"Optimism turns out to not to be mis-placed" shock

[mark_in_manchester]

Did you ever have a blow-up with a likely, expensive and terminal cause, and an unlikely, cheap and easily-fixed alternative possible explanation?

Did you then nurse the vehicle home hoping for the latter, but knowing things always turn out to be due to the former?

Before Christmas I siezed my Ural-Daihatsu on the way home from a friend's funeral. (An MZ rider, he chose cremation but close family forgot the bottle of 2-stroke oil in his casket to accompany him to the other side. It would have been great to see it accompanying him up the chimney).

The engine made loud sounds of distress from the rear, slowed, and stopped. The kickstart was siezed. After 10 minutes it freed off, started (sounding terrible), and I crawled home on it.

Today I plucked up courage, broke the frame in half (it's made that way) and removed the gearbox. One of the 6 set-screws which hold the clutch together had undone itself and started to chew into the gearbox case. Nothing bad enough to need repair - except for replacing one set screw, and putting them all back in with thread lock.

I once read of this happening in an old Cossack Club mag, but barely hoped it would explain away what I really thought was a piston siezure. For once, such optimism has been shown to have been well-founded. Although given the occassion which necessitated the original journey, perhaps such optimism should be considered provisional

[coachgeo]

Im not knowledgable enough to know the in depth workings of any engine but it seems to me the direction to think right now is..... if it was that set screw that did cause a bind that siezed it, the angle of attack once fixing it may lie in.. .... what stresses did that siezure cause and what do to about them? Is there bearings that should be looked at, does it force a piston to move oddly thru a cylinder possibly scaring the walls? What about the crank or crank journals, bearings, etc. Try to decipher what to look out for and how to evaluae thing that got stressed?. Once you decide that I hope for you that what you watch out for turns out to be fine along with everything else.

Should you locktite all your set screws in now? Should all be replaced since they got a crap load of force put on them during that seize?

[mark_in_manchester]

well...the set screw which was on its way out, became the cutting tool in an odd lathe in which the tool was rotating and taking an interrupted cut once per rev, out of a steel plate on the end of the gearbox. Clutch is still true, and siezure was gradual, not a big bang - from the revs it was achieving I'd say the load on the engine before it conked out was similar to running up a shallow incline at tickover. So - although it certainly sounded horrible, I don't think I'll be delving further into the engine (oh - and clutch on this is in the open air, so no need to go fishing for swarf...). Actually this could all be a blessing - I needed motivation to take the engine out and finish welding the frame up properly, in those areas where the presence of an engine had previously dissuaded me...

[mark_in_manchester]

Well...bike made it down to mates in Anglesey (say 130 miles each way) the other weekend, with no major problems. So...perhaps optimism was not misplaced afterall...running fine on 50/50 chip oil, filtered to 1 micron. Even treated it to new oil and filter...whatever next...

[Stuart]

Good stuff! Maybe the rally next

[johnfireball]

Hi Mark,
It's recommended to stake them screws with a centerpunch.
John.

[mark_in_manchester]

John - sure did hit those set screws with a centre punch, as well as thread lock. Belt and braces.

Well, I said 'whatever next'. I put a new clutch cable on, fixed the temp gauge, and soldered a slow leak in the radiator. And then the alternator caught fire. It was soaked in diesel as two-tank plumbing seems to have sprung a leak on the long journey. Of course, this is all nothing compared to the fires of Mouse's sanctification, with which the God of home-brew transportation has seen fit to test his character...would've destroyed the will to live of a mortal such as I...