CVT Bronze bush's, Help needed !

[Dougy]

I've been through a few belts now on the diesel build we done, I was out on it today when it occured to me why, when the engines running but we're not moving the front pully just rubs away on the belt like a little grinder, its smooth but the friction is wrecking the belts, my model cvt does'nt (allegedly) need the bronze bush that comes with other cvt's....but I think it does, I have a copy of a comet tav 20/30 torque converter (a GTC), there have been a few company's copy the design over the years and I've just orded a bronze bush that may fit, part number 200349A, I'm hoping it will fit but even if it does Its not recomended and therefore who knows how it will pan out an why was one not used by the makers anyway ?

My question is does anyone know if I should use this bronze bush ? It will run on steel and I cant really lube it because my belt runs on the same crank and dont want it slipping so is it ok to run them dry ?, I read about oilite bronze bush's which if I've read right come pre-oiled for life ! Is this right ?, they will be Ideal for the job I think over a normal bronze bush but If I dont get them In the size I want can I buy a solid lump and make it myself ? The pto is an Inch thick and theres a sleeve over that where the bronze bearing will run on although I havent measured it yet the inside Id will be approx 30mm I guess. Any thoughts on this.

[gilburton]

If it doesn't fit try http://www.bearingboys.co.uk they have a range of oilite bushes inc 30mm. They are very good and if ordered before 4pm you usually get it next day,
Would a needle roller work??
The aixam cvt has a thin bearing to do the same thing.

[pietenpol2002]

Another option might be to go with a lubrication-free plastic bushing/bearing such as Delrin.

http://www.coorstek.com/resources/8510- ... shings.pdf
http://www.igus.co.uk/default.asp?page= ... &C=GB&L=en

[Dougy]

Thanks for the replys, Gilburton, the bearing boys fella was a really nice guy and gave me a rundown on the oilite bearing which I've gone for, the only problem is that Its to go over the front pully which has an OD of 29mm and there is no standard bearing size for this, so I've gone for a standard one of 30mm which gives 1mm worth of slack (is that normal ? I dont know !). The other option here is getting one machined up but I'm going to try it, I'm going to pick them up tomorrow, I've orded them locally, they where only £2.50 so I bought two, the other thing is the OD which is 35mm so I guess I'll be stretching the belt by at least 6mm but it will still have a good bit of slack left and will be far from rigid, Its all an experiment this so I'll be keeping a watch on how it performs as well as keeping an eye on belt and bush wear.
pietenpol, those plastic bearings you mention look really good, I want to be able to get the servive parts over the counter at any bearing place here in the UK, but saying that I may give them a go yet....thats my plan B .

[coachgeo]

Can you get a 1mm sleeve? Not sure how to lock the sleeve on shaft, though though?

[gilburton]

if the bush seems to work in principal and helps your belt problems I would suggest getting the 28mm bush. The outside dia is 36mm so plenty of room to enlarge it. 29mm is a funny size maybe an imperial bush might be better?? Anyway you don't want it too tight as friction will make it swell so you might find 30mm works well?
The slack will actually be 0.5mm ie 1/2 a mm so it might be just right. The belt stretch will be 3mm.
Bearingboys do actually list 29mm needle roller bearings but the outside dia is 38mm?? ie 4.5mm belt stretch.
The aixam microcar cvt has a very thin width roller bearing which is roughly 1/4" wide(I'm old so I don't do metric lol) which sits centrally under the belt. The belt is quite wide so it doesn't fall off.
I'm not familiar with the comet but will bush width interfere with the pulley movement as it moves in??

[Dougy]

if the bush seems to work in principal and helps your belt problems I would suggest getting the 28mm bush. The outside dia is 36mm so plenty of room to enlarge it. 29mm is a funny size maybe an imperial bush might be better?? Anyway you don't want it too tight as friction will make it swell so you might find 30mm works well?
The slack will actually be 0.5mm ie 1/2 a mm so it might be just right. The belt stretch will be 3mm.
Bearingboys do actually list 29mm needle roller bearings but the outside dia is 38mm?? ie 4.5mm belt stretch.
The aixam microcar cvt has a very thin width roller bearing which is roughly 1/4" wide(I'm old so I don't do metric lol) which sits centrally under the belt. The belt is quite wide so it doesn't fall off.
I'm not familiar with the comet but will bush width interfere with the pulley movement as it moves in??

Hi mate, you've been a big help with this one, THANKS ! After looking at your pic I went low tech and got on the lathe, I quickly realised that the bearing I bought was to big (thick, by 1.5mm !) and this would restrict the front pully advance, I then turned my 20mm long bearing to 15mm, put it on and took it up the road...30 MPH max speed (on another note I, on my build thread for this bike I was trying to restrict my top speed to 30 MPH incase speed / or overheating was a factor in my drive belts breaking, and I just could'nt do it.....untill now, you simply have to stop the front pully from engaging fully ! , then I got it back on the lathe and reduced it to 10mm which equaled a top speed of 35 MPH, then back on the lathe till 7mm which gave me 41.5 MPH, I've still got my throttle screw right in so I can get a bit more speed out of it by opening my throttle a bit further but for now I'm confident that the front pully is opening to the full and I'm getting the best performance possable out of it. When its ticking over now the belt simply rests on the bearing and does'nt wear out ! I'm very happy about this and feel confident enough to go the 20 mile drive to work on it tomororow , in the style of Arnie....I'LL REPORT BACK.

[gilburton]

so you've now got lots of 7mm bushes then

[Dougy]

Yeah mate , three 7mm ones ! And I took my eye off the ball for a bit so theres a 6mm one too ! I'll keep this one and label it 'DANGER !!! HIGH SPEED USE ONLY !!!'
And I'll only use it to get away from Old bill

[gilburton]

The bearing on the aixam is a 61806 30 X 42 x 7 if you have enough slack on the belt ie 6mm this would be the way to go in the long term
You will need some 0.5mm shim steel (or bean tins lol) to make up the 1mm difference and the bearing number is the open bearing but there are also steel and rubber sealed versions. It's listed on bearingboys at around £8 but you should be able to get it locally.
Hope the oilite mod works out
Don't get carried away by all this speed

[gilburton]

Not heard from you for a while? Did the bush mod do the trick??

[Dougy]

Hi mate, I've not had any problems with it at all, Last weekend I went to a party near Blackpool on it, no problems and it goes Great.
When I was first testing it after the build an I was breaking belts left right and Center, I originally thought it was my aggressive riding style, after the fix I continued to ride slow, I then completely chilled out and for a while rode it on the 'Saint' side of sensible, this, on the one hand did end up giving me enormous MPG but was also VERY boring ! I built it to be fun for her to ride after all, so as I gained confidence the belt wasn't going to snap my riding style has got more aggressive again to the point where I blast about everywhere now, like you know if you go too fast too quick or you ride with the throttle wide open but are going slow say up a hill they over fuel like crazy, on a recent MAG demo run I was going up a very steep hill and my mate overtook me and asked was I running it on Coal , the result is my MPG is way down on what I originally stated to about 90 MPG.....I can live with that

[gilburton]

That's good to hear. Such a simple solution Pity it cost a bit in belts/time
The info might help others. Bet you still run with a spare belt though

[Sphere]

Hi mate, I've not had any problems with it at all, Last weekend I went to a party near Blackpool on it, no problems and it goes Great.
When I was first testing it after the build an I was breaking belts left right and Center, I originally thought it was my aggressive riding style, after the fix I continued to ride slow, I then completely chilled out and for a while rode it on the 'Saint' side of sensible, this, on the one hand did end up giving me enormous MPG but was also VERY boring ! I built it to be fun for her to ride after all, so as I gained confidence the belt wasn't going to snap my riding style has got more aggressive again to the point where I blast about everywhere now, like you know if you go too fast too quick or you ride with the throttle wide open but are going slow say up a hill they over fuel like crazy, on a recent MAG demo run I was going up a very steep hill and my mate overtook me and asked was I running it on Coal , the result is my MPG is way down on what I originally stated to about 90 MPG.....I can live with that

Haha, thanks for that, made me laugh. Apparently my Enfield smokes a bit on takeoff as well, but I haven't bothered taping it yet. Though I really should.

[Dougy]

I think I'm going to buy one of the sites 'eat my soot' badges. I must admit on a separate note that I really love the attention having a diesel bike brings, I've only had positive comments of other bikers and public FUN FUN FUN