Yanclone/Suntom 186F No compression fault finding & repairs

[old clunker]

Or how to screw up and fix an Yanclone engine!.... This info is for the installation in a Royal Enfield motorbike, which I hope will be a useful guide for the many converted diesel Enfields out there, and I've found that there is a lack of actual practical technical information about the engine and primary drive conversion.
The engine information applies to the original Japanese Yanmar L100, and it's other Chinese diesel engine copies, such as Changfa, Punsun, Winsun 186F/CF versions.

In the middle of last April, suddenly my Suntom 186F engine decided not to start, and with very little compression after working fine the previous day, so a long and at times tedious process of finally fixing the diesel engine was started two weeks ago! Well, other more important priority things got in the way first!...
The thing to remember about these small diesel engines, is that they give very little warning that they are about to fail, which can be a problem!

The first thing I thought was to check the fuel supply to the injector, and check if it wasn't blocked and check the area for leaks. That was to cause me a lot of headaches in the future!
As I used the electric start, I didn't know that the engine compression was going.

This job can be done with the fuel tank in place; carefully undo the coupling nut with a 17mm spanner and pull out the high pressure metal fuel pipe. Then remove the two 10mm securing nuts and the injector retaining plate. Also disconnect the rubber fuel return pipe from the side of the injector, and stuff a suitable sized bolt in the end of the rubber pipe, otherwise fuel will slowly and relentlessly leak everywhere over the engine.

Then very carefully pull out the injector, it might need a little bit of careful levering out if it is very tightly located.

The copper shims quite often stick to the injector when removed, and you must be careful not to lose any of them! As they affect the injector operation. My one had three very thin shims installed. I stuck them together and in place, with a small smear of Vaseline, which makes life easier when refitting the injector.

After checking the condition of the injector tip and seeing if the four offset 'microscopic' injector nozzles aren't obviously blocked! it was time to see if any fuel is getting to the injector and check the spray pattern.

The pipe coupling is tightened to hand tight, plus around a quarter of a turn 'nipping up' with the spanner - that should prevent leaking. Then reconnect the rubber fuel return pipe from the side of the injector, after removing the bolt.
In the glass Jar you should have four fine spray patterns, and no leaks at the pipe coupling end! This is a high pressure system, so you have to be a little bit careful about high pressure fuel, and take precautions.

In my case, that looked ok, so it was time to really start taking things apart! The fuel tank has to come off now, plus the exhaust manifold and air filter.

Now I have to take off the rocker cover and cylinder head, as I noticed a small oil leak from the front of the cylinder.

Be careful when you take off the rocker cover and the four cylinder head bolts, since the rocker arms aren't fixed in one place,(they are normally held in place when the rocker cover is fitted) and can slide off the rocker shaft. My exhaust valve rocker always wanted to slide off for some reason, when not restrained!!

Time to take off the cylinder head, which is heavier than you think! well, it's a diesel engine!!! Make sure that tappets stay in place and don't get mixed up! I placed some paper towel to keep them in place, and stop unwanted items to fall into the tappet housing, which is quite wide.

Now we can see the mess on the cylinder head face and inlet and exhaust valves, created by my last unsuccessful bio-ethanol.vegetable oil mix - you have been warned now!!!

With the engine cylinder, you can easily see where the copper head gasket has blown, and the carbon crud deposits on the piston crown. The barrel honing pattern and condition looks good, just very oily! The combustion/swirl recess in the piston can also be seen, also clogged up.

So lots of time now spent carefully scraping and cleaning off the very hard carbon crust, on both the cylinder head and piston, which was a very dirty and boring job - that crud sticks to the surfaces like the proverbial s**t to a blanket!!!!
It's then time to inspect the valves and valve seats. Luckily I still have a very old car valve spring compressor lying around. Just brush off the dust and cobwebs, and it's ideal for the job!

Have to be careful that the valves, springs, spring retaining collets and seals don't get lost or mixed up! I found each valve and valve seat in good condition, but needed careful crud removal to get a good seal.

The cylinder head castings look quite well manufactured, it's just some the machining details on the mating faces in places, that lets the overall quality of the engine down. I suppose it's down to Chinese practice of meeting manufacturing quantity targets, rather than quality control targets. I found some small imperfections in the area where the cylinder head gasket had blown, so I used some fine emery paper and blended down the rough area as much as I could. I also went over the whole cylinder head mating surface and piston crown, with the fine emery paper to give a smooth finish again.
Time to refit the valves in the same way as they had come apart, with hopefully nothing left over!

[old clunker]

Eventually I got around to cleaning out the carbon in the combustion recess, and foolishly I thought that it looked like the piston rings weren't gummed up!
Also can be noticed the piston identification number, and the 'F' for correct piston location, which always faces the primary drive output side.

Next, I have to replace the copper head gasket with a new one, put a very thin smear of head gasket silicone sealing compound over the blended imperfection area, and put the cylinder head back on.

Thinking that I had done enough, I tightened the four cylinder head bolts up diagonally in two stages. Finally torque loaded up to 40 ft lbs.
Then I was time to refit/reconnect everything else, adjust the tappets/valve clearances to 0.15mm/50 thou inch gap at piston TDC, also marked as a 0 on the top of the flywheel/cooling fan assembly.

At last everything was back together again, only to find that the compression was a bit better, but the engine still didn't start! I have to get really serious with the engine now, as I found that there was also an oil leak from the bottom of the crankcase gasket, when I tried to start the engine, so it looks like the gasket has also blown!
The next instalment of this saga is to come soon.... with hopefully a happy ending?!

[coachgeo]

Wonder if having a machine shop take the piston top swirl cup and smooth it out will help what ever fuel you put into it automize better. Those cups look like your in space looking down at a moonscape mountain and valley. Course the imperfections might help though (splash automization more so than swirl automization?) What areas in the cup does it appear to you that the injector spray hit and at what approx angle? Straight down w/each of the sprays hitting 4 corners of the valley in the cup.... or each hitting a different side of the center mountain orrr???

[old clunker]

Hello Coach, the black rough looking 'moonscape' as you put it! is due to the irregular build up of carbon, due to incomplete fuel combustion in the combustion recess in the piston head.
It took me about a hour to carefully scrape the majority of the crud out, and also using some fine emery paper, to get the finish back nearer to the original smooth cast alloy profile, with a smoother cone shape in the middle for the fuel swirling process.

What the piston design needs is a less or different heat conducting metal insert, such as stainless steel in the combustion recess, and a glow plug fitted to the cylinder head to give more complete fuel combustion of alternative fuels. Unfortunately diesel engine manufacturers can't be bothered/or it's not in their interests to do so.

The injector is set into the cylinder head at an angle of about 30 degrees approx. from vertical, and it looks like with the 4 spray injector pattern, each hits a different side of the cup and cone, in the piston crown.

[henneberg]

Could the cause of the missing compression be hard carbon veg crust at the piston rings

[old clunker]

Partially Henneberg, and a bit more complicated as you will see!

[old clunker]

So round one of the "competition" was won by the engine, but I'm determined to win round two!

You have to have a reasonable set of tools to do this, and be prepared for a very oily, messy and sometimes tricky job! Patience and a sense of humour at times, is also an essential requirement!

I took the engine oil sump plug out (rear facing at the back of the engine) and left the engine oil to drain out overnight into my used oil tin. It's no problem, as the engine was due for an oil change after about 550 miles, and was turning a murky black colour anyway.

First the rear brake pedal has to be disconnected from the rear brake rod arm and brake switch lever. Have to make sure that it is carefully disconnected, otherwise you could end up with a broken rear brake light micro switch as well! and also try not to lose the split pin used.
The rear brake pedal then drops out of the way, and now the left foot peg can also be unbolted.

At last the primary chaincase cover can be loosened off; with plenty of old newspaper and a oil tin ready to catch the approx. 420 ml of engine oil or automatic transmisssion fluid - whichever you prefer to use.
Unfortunately the chaincase has no drain plug, just the oil filler plug and a small oil level screw like plug, on it's forward lower half. So it's going to be a messy job to drain!

You get a good view of the engine drive sprocket, the duplex primary drive 'endless' chain and the larger clutch assembly sprocket, all suitably very oily, slippery and messy to handle!

Here's a close up of the engine sprocket, secured by two quite large and stiff allen head grub screws.

You can also see the 'slipper' type primary chain adjuster, which is also unbolted and removed.

And a close up of the clutch sprocket and assembly, so you know what it should look like again, when you hopefully get it all back together!

Despite what the scarce found information in the few manuals around say, I found that trying to put the engine in gear, and locking up the rear brake, didn't work in stopping the engine turning over. The easiest and most reliable method I found, was to use a small but strong piece of square sectioned hard grained wood, and let it jam in between the engine sprocket and primary chain. That was effective in stopping the engine turning over...... I had no problems with bits of wood getting mixed up in the chain and sprocket. The sprocket teeth just left large marks in the wood. If you are worried about wood splintering, you could wrap the wood in an old cloth.

Now the engine is locked in place the engine shaft bolt can be undone, and a 13 mm socket fits, and the bolt unscrews anticlockwise. The spring washer and penny washer can now be removed, and the old Loctite thread adhesive can be scraped off. The engine output shaft has a welded woodruff type locating key in position, so don't bother trying to get it off! Lucky for me that I have an old impact driver with hardened steel bits, and a hex headed one that fitted perfectly!
The two sprocket securing grubscrews are a bit stiff, but are fairly easily removed with the impact driver.

Another useful old car tool to have available, is a gear puller, which I used to pull the initially stiff engine sprocket out, after the securing grub screws had been removed. When the sprocket was loose on the shaft, I now started to dismantle the clutch assembly.

The three clutch spring pin bolts are now loosened off evenly in turn, with a 11mm or is it a 12mm socket? since they are sprung loaded, and the clutch cap plate, springs and pin bolts are carefully removed and stored, in the exact order they came off.

We're getting close to the interesting bit now!! The outer clutch plate can be removed with the other clutch plates, and it's best to keep them in exactly the same order that they came off! when storing them. A quick inspection for wear, locating splines are smooth and free from wear, and the backplate is not warped. Mine were in good condition and clean.

The greasy clutch pad rod is now removed, and you'll also find that a small ball bearing will also pop out behind, when you least expect it! lucky for me that I found it, when it fell out. Without the tiny ball bearing fitted, the clutch wont work!! so keep it safe!

The clutch centre and assembly is held on with a large securing nut and circlip. After locking the clutch sprocket assembly in place with the brake bar, and then removing the large securing nut, I preferred to leave the circlip in position, and take it off later.
A clutch centre extractor (PED2005) using the original three clutch spring pin bolts, and brake bar (PED2025) or equivalent, makes the clutch sprocket removal relatively easy.

I jammed the brake bar against the rear brake pedal, which made things easier when removing the clutch, and freed up one hand.
The engine sprocket and primary chain and clutch sprocket, can now be removed together, and placed in a clean safe place out of the way.

[Sphere]

Press on! I don't like this sight, but I have to take it apart again soon, my sec. drive sprocket wobbles ever so slightly

[old clunker]

The engine sprocket, primary drive chain and clutch sprocket and assembly, checked for condition and now stored out of the way.
The engine sprocket is a split assembly when removed. The inner split part is separate from the outer toothed part. When the grub screws are fitted, it expands the inner part of the sprocket, which also expands and grips both the engine drive shaft and the outer toothed sprocket, with an interference fit.

At last I'm just left with the inner chaincase, which just has a few securing bolts and a plate to remove - we're almost at the engine now!

There's just four allen bolts and a inner chaincase flange plate assembly with a metal bush insert to remove - the flange plate is secured with 4 hex head bolts.
The four allen bolts are removed first with the impact driver and hex bit, some of them are quite stiff to move. Also noticed was an oil leak from the crankcase rubber oil seal. Part of the oil seal lip wasn't in contact with the driveshaft properly, and the oil seal had appeared to be 'blown', as indicated.

Next was to remove the four chaincase flange securing bolts with a 10mm socket and ratchet wrench. You have to be careful removing the flange assembly here, as there is a paper gasket behind and a rubber oil seal also in the assembly. Both can be easily damaged during flange removal.

Now we can use a little bit of controlled "brute force" on the chaincase! with a metal bar. This is to break the seal caused by the original thin layer of silicone gasket jointing sealant used between the chaincase and the large drive shaft adaptor collar.

After all this work, the engine crankcase and gearbox drive sprocket are revealed!

In my case, a green coloured paper gasket is used to provide an oil tight seal for the chaincase flange assembly, which can be seen.

More to come fairly soon.... It gets really messy with the engine!!

[old clunker]

I've now got access to the oil filter, which is a tight push fit, secured by a bolt on the r/h side. A 10mm socket fits.
Be prepared for some more thick black old oil to leak out!

Looking at it, I'm lucky that there's no small metal particles in the filter. Just needs cleaning up.

Now to put it safely away with all the other bits removed, before I lose anything!

At this point, it feels like I have dismantled nearly half of the motorbike, as the fuel tank is removed, exhaust has to be disconnected, high pressure fuel pipe and injector disconnected, canister fuel filter assembly unbolted, air filter unscrewed, cylinder head removed etc...etc... have I left anything out?!!

Because the motorbike and the diesel engine are very heavy, and I have a bad back and knees - the Royal Enfield is about the heaviest motorbike I can cope with, pushing around in and out of the garage, and I'm not getting any younger!! It's worth considering this when buying or building a diesel motorbike, especially when doing serious maintenance on it.
With these considerations, I decided to do the work with the engine in place, and remove the two nearest engine bolts, and just loosen off the ones on the other side of the engine.
Then I can jack up the engine under the sump to access the lower crankcase bolts, that are obscured by the bike frame.
At least I can sit down most of the time, whilst doing the work.

The first thing to do was to number the crankcase bolts as shown in the Yanmar L100 PDF manual, as they eventually have to be tightened up in a specific diagonal order, for the crankcase to be tightened correctly. So I removed them in the same order, loosening them off in stages, using a 12mm socket and ratchet. Then when I got to the difficult to remove bolts at the crankcase bottom, I removed the required engine bolts and jacked up the engine just enough for access, using a trolley jack under the engine sump. Then don't forget to take the oil filler plug/dipstick out!

The crankcase can then be carefully prised apart, and despite it leaking oil at the bottom, needed some quite strong blows with a plastic faced mallet to separate the halves. It eventually came away, with even more old oil leaking out everywhere on the floor. It's amazing that after being left to drain overnight, there's still lots of the horrible old oil "lurking" around in every corner of the engine! Finding any excuse to cover your hands and tools with it.
A "Jeremy Clarkson" style motoring metaphor for it all would be: - " The engine oil's like a alcoholic going home after a Saturday night drinking binge; spewing up all night and randomly into the next day as well!"

For some strange reason the balancer shaft assembly came off with the crankcase, rather than remain in with engine. I took it off eventually, though it was a tight fit in it's crankcase bearing, and refitted it to the engine before re-assembly. Also seen, is the nylon gear assembly of the engine governor, a remarkably small device!

Enough 'waffling on' for now - hopefully back again soon?!

[Sphere]

At this point, it feels like I have dismantled nearly half of the motorbike, as the fuel tank is removed, exhaust has to be disconnected, high pressure fuel pipe and injector disconnected, canister fuel filter assembly unbolted, air filter unscrewed, cylinder head removed etc...etc... have I left anything out?!!

I don't you need to dismantle the thingie in the lowerright corner (in your tin) from the inner primary cover. Should save you some work next time? I would like to say thanks for another thread with pics, I love it

[old clunker]

Glad that you enjoy my engine experiences Sphere! the reason why I took the inner chaincase flange assembly off, is that it made taking the chaincase off easier, as it fitted quite tightly on the slotted shaft, which could damage the internal rubber seal in the flange. I wasn't looking for extra work and things to remove!!!

[Rhynri]

My favorite thing about this kind of work is that *POCK* sound that that gasket sealer makes when it gives way. Odd, I know, but its the little things that make life fun.

[old clunker]

Back again after a welcome weekend break!
Now the inside of the "Yanclone" diesel engine can be seen in it's oily glory! There's not much in there, though what's there is heavy duty....

The crankshaft has 'F' markings etched facing the crankcase, to aid in correct fitting, and the large gear assembly on the right is the camshaft.
There are also alignment/timing marks visible on both gear wheels.
Overall the condition looked good inside the engine, and following the old engineering adage:- "If it ain't broke, don't fix it!" so I didn't pull the camshaft assembly out, which would have meant removing the tappets, and loosening off the fuel pump. As it looked ok - best leave it alone, so a bit less work to do!

A closer look at the crankcase showed the source of the slow oil leak, after the engine wouldn't start.
The aluminium gasket had been fitted with some distortion and a crease at the bottom edge of the crankcase, and with a very thin layer of gasket sealant applied by the manufacturer, was an oil leak waiting to happen! It looks like they were trying to save money on sealant as well.

After cleaning it all up, definitely time to replace the metal gasket.

The engine speed governor can also been seen more closely now on the right. Seeing Japanese bearings fitted in the crankcase provided some re-assurance - even the Chinese don't appear to trust fitting their own manufactured bearings! The component and casting quality appears to be quite good.

Closely looking at the crankshaft rubber oil seal set into the crankcase, I could see that the seal lip on one side wasn't seated on the crankshaft properly, causing an oil leak, and possibly helping in the lack of engine compression.

The 45mm internal diameter oil seal has the identification 35 50 10, when it comes to ordering a spare.

I can now get on with removing the piston and con rod. The piston has to be at TDC to get access to the two con rod bolts. A 13mm socket fits the con rod bearing cup bolts.

Don't be surprised by having to use an extension bar/tube eventually with the socket/ratchet, as the bolts are a very tight fit, and loosen off with a bit of a crack!

The lower big end bearing cap can be removed from the tight space.

The white metal bearings looked in good condition, and nice and oily, so plenty of lubrication is happening, which is a good sign.

I'm getting to know this cylinder head very well now! A second time I've had to dismantle things off it and remove the head.....

At last the cylinder head can be removed, and make sure that the tappet rods stay in the right place, and nothing falls into the large gap, by stuffing a rag or kitchen paper towel in.

It's piston time again! but now to remove it.

Despite the rings being gummed up and not providing a sufficient seal in the barrel, the piston was still a tight fit in the bore, and I had to knock it upwards using the wooden shaft of a small hammer placed under the piston, and then given some sharp taps.

Some more piston experiences hopefully to come soon......

[pietenpol2002]

Great series on your tear down Clunker. I'm greatly enjoying the read. Keep it coming.

[old clunker]

Thanks for the comments Pietenpol2002, glad you like it!

Continuing on again, after some effort the piston could be carefully pulled out of the barrel.

At last the piston is out!

The sides of the piston needed careful cleaning; again scraping off the carbon crud off the affected surfaces. The three piston rings were found to be gummed up, and not providing a proper gas tight seal any more.
So lots of time was spent cleaning up the piston sides, and freeing up the rings, until they are able to move in the piston grooves again.
It's at this point that I made a big mistake. I had a feeling that the rings should be replaced , but trying to save time and money - the replacement rings would have taken a couple of days to arrive, so I decided that cleaning would be enough and I could put it all back together.
From my experiences, It's always best to replace the piston rings at this point with new ones, and if any are jammed and cannot be removed, then replace the piston as well.
This would have saved me a lot of extra work in the end!

The bore can now be inspected closely, and found to be in good condition wear wise, so a smear of new engine oil was applied to its sides, to aid piston refitting.

The crankshaft bearing surface can also be seen and inspected, and some new engine oil is also applied.

When refitting the piston, make sure that the big end bearing cap number identification marks match up, so the piston is correctly attached to the crankshaft again.

Also new engine oil was applied to the bearing shells, and it's all now ready to refit!

More piston experiences to come.....

[Sphere]

It seems we are in for a nasty surprise, although it appears to water under the bridge for you already!

[old clunker]

Yes Sphere, without trying to give away too much of the engine story away for now! I got the engine working again o.k for one day, started it many times and had it running for over 15 minutes, and idling well . And then the next day it wouldn't start again when I was working on the fuel system!
Just slightly frustrating, and all due to a seized top piston ring!
Should have changed them all when I had the opportunity.....

[TnFan]

Hey Old Clunker!
Been following your repairs with great interest.
Youy pictures and descriptions have been most generous .... Thank You.

What (again) was the WVO fuel method/mix were you were using?
TnFan

[old clunker]

That's great TnFan that you've been finding my engine 'ramblings' interesting.
Hope people find it useful.

My last 'vegefuel' mix was a bio-ethanol/vegetable oil, with a little bit of petrol blend (to try to emulsify the ethanol). The engine didn't like it much! and I don't recommend using this experimental mix, after running the bike over 50 miles with this fuel.
Previous to that, it was white spirit/vegetable oil mix, which I have explained in my alternative fuel post. The engine appeared to run ok on that blend, though looking closely at the injector and combustion area, they don't look robust enough over the long term, unlike with car diesel engines.
You have to be very careful when experimenting with small diesel engines, as the designs are very refined to run on Diesel; and what vegetable blends found on the web (eg.Peter Schur with the now quite vague description of it, that still remains now on a few info boards) that appears to work with cars, doesn't necessarily work with these small engines.

Keep on experimenting but be aware of this......

[old clunker]

Back again, after a rest!

After a good scraping and clean, the piston was ready to refit. Rather than spending at least £12.99 at Halfords on a piston spring compressor tool, which would hardly be used, I decided to make my own using a Jubilee clip kit, which I had lying around the garage and cost under £2! With plenty left to make more clips
The piston sides were lightly smeared with new engine oil, and the large Jubilee clip just tightened enough to compress the piston rings, but could slide slightly.

The piston was carefully centred up with the engine barrel, and slowly pushed in, as it's a tight fit, and the big end, approximately located on the crank shaft.

Now the piston has to be carefully tapped in with a plastic faced mallet. When this is done, the Jubilee clip slides upwards, releasing the piston rings. The piston is tapped down, until it is level with the top of the barrel, and the big end bearing shell is in place on the crankshaft bearing face.

To fit the bottom crankshaft big end bearing cap, the piston has to be at TDC, and the alignment marks have to be lined up for engine timing purposes.

Check the crankshaft and camshaft gear alignment marks line up as shown.

The bottom bearing cap can now be fitted and tightened up. A torque loading figure is given for the two bolts (28lb-ft), but there's no way realistically I can see to get a torque wrench in there, let alone turn it!! I just tightened the bolts up to approx. hand tight, then tightened them up again about a quarter/half a turn. It's a "rule of thumb" that usually works for me in most cases, when you can't torque load something, due to access or no figures available.

I can now apply a bit more generous amount of Loctite black engine gasket sealant to the now cleaned crankcase faces, and fit my nice new shiny metal crankcase gasket - this time with no creases and distortions!
You get about 15 minutes using Loctite sealant to fit the crankcase, whilst the sealant is still tacky.

The bearings were also smeared with some new engine oil, before the crankcase cover is refitted. The rubber oil seal has a bit of engine general purpose grease smeared on its lips, so it will give a good seal when re-fitted around the crankshaft.

It's all ready to fit the crankcase bolts, with the engine jacked up a bit, so the lower bolts can be fitted and accessed. Using a 12mm socket and ratchet, the bolts are tightened up in specific diagonal order twice, until ready to be torque loaded in diagonal order to 15 lb-ft. Don't forget the two longer engine stiffener bolts, which are tightened and torque loaded after the crankcase bolts have been done. These are in the lower middle half of the crankcase cover.

All of this ensures that the crankcase cover gives a proper even seal, and there should be no oil leaks!
The trolley jack can now be removed, and the engine mounts now bolted back in position.

Crankcase cover greased oil seal lips are pushed carefully into position with a wooden spatula - or ice lolly stick! whatever you have!
This now gives a good seal, and should prevent leaks.

The cylinder head can now be refitted, torque loaded in two stages to 40 lb-ft; and the piston TDC 0 mark is checked on the top of the flywheel against the notch mark on the engine cylinder casting. Now the tappets are adjusted again to 0.15mm gap, so the engine should eventually run!


The rest of the engine/clutch refits are just the repeat of the removal process.

[old clunker]

Some Loctite gasket sealant is also applied to the back mating faces of the primary chaincase assembly before refitting. This also helps prevent oil leaks.

The primary chaincase assembly is refitted whilst the Loctite is still tacky, and then the clutch assembly can be refitted.

With the special clutch holding tool, the clutch assembly nut can be tightened and torque loaded to 40 lb-ft.

The rest of the clutch plates/assembly can be refitted, with the primary drive chain/sprocket. The engine drive sprocket bolt, is also torque loaded to 40 lb-ft.

At this point it's best to check clutch operation. For some strange reason, my clutch cable end came off on the actuator arm in the gearbox, so I had to take the outer cover off, and re-attach it to the arm, and adjust the clutch movement setting with the clutch adjuster nut and screw thread.
When that was done, the correct operation of the clutch pad rod could be checked, and the clutch plates seen to move smoothly.
Now I could fit the primary chaincase cover, and tighten it very carefully to about 20lb-ft. That's around the tightness required to prevent oil leaks! They claim 12lb-ft, but it's not enough....

Then fill up the chaincase with about 420ml of engine oil SAE 10 or 15w 40, or automatic transmission oil.

The engine can now be filled with 1.2 litres in my case, of reasonable quality engine oil . The manual claims 1.65 litres oil capacity, but I can only get 1.2 into it, before it starts to seep out of the oil filler neck, so 1.2 litres it is! After running the engine, the oil level is still the same, so I don't know where they got the 1.65L figure from?!

Make sure everything is back together again and tightened up, and nothing is leftover in the parts tin!

After turning the engine over a couple of times, with the fuel solenoid powered, I was surprised that the engine started up third go, running on straight diesel fuel this time, and only the engine idle setting needed adjustment. It ran well, and I stopped and started the engine several times, and had it running for over 15 minutes - it was too good to be true though! and it appeared that I had won round two of the engine contest!

But the engine had other ideas, and it won round three I tried to start it the next day, but found fuel leaking from the injector coupling. The new cheap replacement injector I had got in April had developed an internal leak, and there is no economical way of repairing it! Also the high pressure metal fuel pipe coupling was staring to cross thread, so that had to be replaced as well. I had to get a much more expensive Yanmar compatible copy replacement injector in the end.
It looks like both the injector and high pressure fuel pipe don't like being disturbed much, and should be left alone as much as possible. if they are removed/disconnected more than about half a dozen times, there is a high chance of fuelling problems and leaks. You have been warned!!! The quality of the high pressure fuel components can be marginal.

After a few days, when I got the spare parts and replaced them, only to find that I had got an air lock in the large canister fuel filter, which took some time to get rid of. Then after trying to start the engine many times afterwards, found that the engine compression had dropped off again!

It looks like the top piston ring, which I thought was marginal in operation, has now seized, hence the lack of sufficient compression to start and run the engine.

So I've now got a replacement set of piston rings and a new piston, just in case I damage the ring grooves in the original piston, when trying to remove the seized top ring, which is highly likely! Luckily a new piston isn't that expensive - a lot cheaper than an injector!
The saga continues.... I'm determined to win the final round four of the engine competition!

Watch this space.....

[alexanderfoti]

Lots of really good information in this thread!

[Rhynri]

I agree, i've learned a lot from watching this space.

[old clunker]

Thanks for all the comments.

I'll keep you all informed of what happens next - eventually!

[old clunker]

Armed with a shiny new piston and piston rings, its now round four of the engine contest, and I'm determined to win it by a knock-out!!
Over the weekend I summoned enough enthusiasm to take the engine apart yet again. It took two and a half days from start to finish, to pull everything apart and put it back together, so the motorbike was ready to run, and clear up the mess!I've certainly now got plenty of experience of working on these diesel engines now....

There's three piston rings fitted, the top one is the 1st compression ring, the next lower one is the 2nd compression ring, and the bottom one is the oil control ring. Each one has a different profile, and has to be fitted in the correct order, and the open ends, are spaced 120 degrees apart, to provide the correct pressure seal/piston compression.
If either of the compression rings isn't working correctly, the engine won't reliably start or run properly, as I have found out the hard way!!

Anyway, back to the process of pulling the engine apart yet again, and removing the piston and con rod. When I got it on the bench vice, I first tried to salvage the usable piston rings, by carefully removing them with the help of two feeler gauges. The piston rings are hard but brittle, and don't like being opened up too much, when trying to slide them on and off the piston. This can cause them to crack! One useful tip I found, was dealing with the seized top ring, by tapping quite hard it many times all around it's circumference with a plastic faced mallet. This eventually released the ring that was jammed in the piston groove, so it could be eventually removed. A small bit of damage was done to the piston side by the groove, so it was a good idea to have a new piston available. It looks like the oil control ring and the 2nd compression ring could be used again for spares, if I'm getting desperate!
I could now remove the two circlips securing the piston pin. There's no mention of them in any manual, and it does help a little bit if you have a cheap old pair of circlip pliers handy, as they are a tight fit!

There's also mention in the manual of heating the piston up evenly to about 80 degrees C in an oil bath, for piston pin removal - but since I haven't seen an oil bath for over 30 years now, when I did my engineering training, I'm not about to bother with one now! I just used an electric heat gun to evenly heat the piston to temperature, when I could just about handle it without getting burnt fingers!

When it's hot enough, I could now bash the pin out with a suitable diameter wooden drift and hammer, and the piston pin came out quite steadily without jamming, much to my relief.

And here it is, still warm in my hands! A good condition piston pin, with no wear, signs of scoring, or free play, when it was connecting the con rod. Just some oil staining marks, which provide a useful position guide when refitting.

Now to quickly fit the new piston. I first oiled up all the piston bearing faces, the piston pin, and the con rod small end bearing.

Then heated up the new piston and gently tapped the pin back in as squarely as I could, just enough, so I could attach the small end of the con rod. It's a bit tricky but after a second attempt, it all came together and I could knock the pin right through with the con rod attached.

The piston pin has to be tapped through just enough, so a groove is visible on both sides of the piston pin for the locking circlips to fit into.

[old clunker]

Finally the locking circlips can be snapped into the piston pin grooves, and the new piston rings can now be fitted.

The order I used to fit the piston rings, was the bottom one first then work upwards. The oil ring spring is first fitted into the bottom piston groove, the the oil ring placed over it. The ring end gap is placed facing the exhaust valve side.

Using suitable diameter feeler gauge blades!! I could now slide the second compression ring very carefully into it's groove with the manufacturer's stamp facing upwards, and the ring gap 120 degrees clockwise from the oil ring gap.

Finally the top ring is fitted, again with the manufacturer's stamp facing upwards, and gap facing the inlet valve.

What a relief, it's all done now and it's very noticeable how much more 'springy' the new rings are, compared to the original ones, so that should give much better engine compression. Checked that the con rod moves smoothly and is securely attached to the piston, and there is no side to side free play. It all looks good now.

Next is the repeated laborious process of refitting the piston, oiling every moving surface up lightly, compressing the rings to get it back into the engine bore - also noticing that the new piston is a better tighter fit in the barrel than the original one!
Everything went back together all right, but just had some hassle with the chaincase flange refit; and fitting the exhaust, with a securing nut that had just decided to start stripping some of its internal thread.
Whilst I had the opportunity, I also fitted a low oil pressure warning switch to the crankcase, and wired it up to the spare unused neutral light, so I could use it as no-go warning light, if it comes on when the engine is running, and also acts a reminder when the ignition switch is left in the on position. it's a job I have been wanting to do for some time now, as they are not fitted as standard to diesel engines, as it is a Yanmar optional extra to fit.

Then fill up with oil and check everything for leaks after a while, and for any loose nuts and bolts around on the engine!

Eventually I'll put up a post for fitting a low oil pressure switch to a 'Yanclone' engine....
It's good be a bit paranoid about these small diesel engines, and they give little or no warning that they are about to fail, and can try to run themselves to destruction, with little or no engine oil!!

So on Saturday, it was time for a test start! After first manually turning the engine over several times to get the oil "sloshing" around the engine, and then turning it over with the fuel solenoid powered. Several attempts were made to start it, with lots of smoke and the engine trying to run, whilst there was still a lot of air in the fuel lines. It's a good sign, as a diesel engine should try to start even with very small amounts of fuel.
After a while, it came to life and then idled really well for an engine that has had major work done to it!

On the second start, I then videoed the event to prove that it wasn't a dream to myself!!! and to show you that it actually works. The engine now fires up with just a short push on the start button, and starts much more readily than in the past.

http://youtu.be/nREAcbrJFK0

I was filming this in a space just about large enough to park a push bike in! and was lucky that I didn't trip up on all the tools and bike bits lying around on the garage floor. So I was more concerned about my safety than video quality!
At times I thought I would never get the engine running again, but it's just down to "bloody minded" perseverance that I got it working again, so I've won the engine contest at last! I hope that this gives hope to people out there with a "Yanclone" engine that wont start or run.

I found that the engine is now much more "revvy", and responsive than the original set up, so it looks like the new piston and rings are a better match for the engine barrel - it's those Chinese manufacturing 'tolerances' again, and you just have to get lucky! So now it appears after a lot of work, that I have now got a decent diesel engine, with Japanese main bearings fitted. Should last for some time now....
Also adjusted the throttle linkage, and had to adjust the clutch yet again, using the gearbox access clutch adjuster and lock nut. When you get it right after some trial and error, it really does make a change to the smoothness of the gearbox operation.

Finally after checking for any fuel and oil leaks - it's all leak tight now, and with the final check for loose nuts and bolts, and rear brake operation, "Clunkie" is now back on the road, and I did just over 13 miles yesterday afternoon on the motorbike, with different road and traffic conditions to test the bike out. Only after being off the road for nearly 4 and a half months!
When I was riding the motorbike, I forgave it for all the hassle it had given me, with the bike's excellent road holding and handling on our local pot holed and neglected roads. I can see why it's still so popular in India; and despite its now primitive (and in my case, non-symmetrical) frame design, designed back in the late 1940's austerity Britain (it's strange how things go in circles?!) The handling of this 'ancient' motorbike design is far superior to all the Japanese commuter motorbikes I have ridden in the past.

[alexanderfoti]

Looks and sounds great! Glad you had some luck finally! Is your chaincase still going to fit with the oil pressure switch in place?

[old clunker]

Thanks for that; the chaincase fits perfectly over the oil pressure switch, when fully screwed in place into the crankcase. Just had to bend the connector tab up a bit for the cable connector, and the cable is free from the chaincase.

[old clunker]

Finally, a summary of what I have had to replace and do, to get the engine running normally again:

The cylinder head gasket had blown which needed replacing, and the cylinder head and valves had to be cleaned of incomplete 'vegefuel' combustion carbon build up.
Both the metal crankcase gasket and engine output shaft rubber oil seal had blown, due to the compression pressure leakage past the now gummed up and seized piston rings. These were replaced.
The piston and rings were replaced, because of the above, and the piston can be easily damaged when removing old piston rings, so it's a good precaution.
The injector nozzles got sooted up with carbon/incompletely burnt fuel, and was and beyond cleaning, and there's no way of economically dismantling them and overhauling, so it's another replacement job.
If the fuel system components are disturbed too much - they generally like to be left alone as much as possible! the injector starts to leak fuel internally, and the metal high pressure fuel pipe couplings start to leak and cross thread, so they had to be replaced.
With injectors, it's best to get the more expensive Yanmar part number equivalent replacement from L&S Engineering. I originally got a cheaper one, and it soon developed a serious internal fuel leak which made it useless! The L&S one works really well in comparison, and is better than the original fitted injector!

Then when everything is back together, get rid of the old and now contaminated oil, and put some decent oil in the engine! compression should be restored, and it should start and run easily for a change!

These two spare parts suppliers, which I have found very useful:

Direct Equipment Sales
Unit 17, Arden Business Centre , Arden Road, Alcester, B49 6HW
telephone on: 01789 765827 - generally cheapest price bits, though fuel injectors can be variable quality.
The rest of the spares are quite good for Yanclones.
http://www.directequipmentsales.co.uk/page11.htm

L&S Engineers - directly use Yanmar L100 part numbers to supply equivalent quality replacement parts.
West Coppice Road, Coppice Side Ind. Est. Brownhills,Walsall,West Midlands,United Kingdom
WS8 7HB
General Enquiries: 01543 378189 - more expensive but parts tend to be Yanmar L100 direct equivalent spares.
http://www.lsengineers.co.uk/crankshaft ... -l100.html

Both are helpful and supply spares very quickly, between 24 to 48 hrs of ordering.

What had appeared to happen, was that the last vegefuel blend had caused the minimal cylinder head space dimensions between the piston, and the combustion compression recess cup to slowly reduce beyond a critical point, due to the build up of carbon on the surfaces; where the engine appeared to start and run at low revs normally, but the greatly increased compression pressure in an even more tiny space suddenly blew the head gasket and the other gasket and oil seal. Plus the incomplete vegefuel combustion carbon build up on the injector nozzles stopped the injector from working efficiently, and I found that two of the nozzles were completely blocked.

After closely looking at the engine internals - not through choice! I'm impressed with the design, how it uses the minimum amount of materials to produce a small but relatively strong and compact diesel engine, that's extremely optimized to run on diesel, with a very small efficient injector, but it's not robust. Also the bearings are compact and just big enough to do the job of allowing the engine to run all day, every day, at the engine's rated maximum rpm, producing the maximum rated HP reliably.
With the minimalist engine internals, it looks like they are just not designed to take stresses beyond the tight design limits, such as trying to increase maximum rpm, and fitting Turbos. This would just wear the engine out in no time at all, with expensive repairs, if still economically viable. These Yanmar L100 based engines seem to be a good compromise design to give diesel fuel consumption efficiency in a relatively small size.
I've found that the "Yanclones" are only let down by the quality of some of the components sometimes fitted. When you get them sorted out, it's a good reliable engine within its fairly narrow operating design limits, so not that good an engine to experiment with!

Better off playing around with unfortunately more expensive and larger engines, such as the Punsun V twin, or other twin cylinder diesel engines, as they are potentially more robust internally, due to larger engine size and weight!