HELP!! Setting up a Clutch Bell

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goodgamer

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I have a XTM Mammoth that has not ran in awhile because of clutch bell issues. The top bearing keeps breaking. So earlier I went to my LHS they race only electric but I figure they would know about nitros. The guy not best people person gave me a bearing that fit for $2.50! So I just bought it anyway cause I wanted to smell burning nitro. :) I went home sarted to screw it in and it broke! :( The outside of the bearing fit snug with the inside of my clutch bell. If that makes any sense. But what am I doing wrong? Any tips? I went through Rolex's post about clutch's.
 
What is it that your breaking? Which is the "top" bearing? The bearing in the bell closest to the engine or furthest from the engine?
 
The bearing furthest from the engine.
 
It sounds like your not shimmed properly or something. When you have the bell screw tightened down all the way, you should be able to push/pull the bell just a tick (1/2mm) so that the bearings have absolutely no side load from the screw.

Granted, the two speed setup on the mammoth makes the bearing prone to fail, you should still get half a gallon out of it before having to put in a new bearing. I ran cheap bearings when I had my mammoth and didn't have the issues your having. I used boca green seal, fast eddy and avid yellow/metal shielded bearings. So nothing high $ by any means. I run fast eddy and avid's now all the time. I don't bother with boca's as the cheap ones seem to last just as long.
 
Ok, What sizes were they?
 
Typical 5mm ID x 10mm OD x 4mm wide, for standard 1/8 cb bearings. I keep 5+ on hand and usually buy bearings in packs of 10. I have enough sizes in a drawer from various vehicles over the years to open a hobby shop!

I usually run these:
http://www.avidrc.com/product/8/metric-bearings/1/5x10x4-Revolution-MR105-RSZ-metric-bearings.html

Or these:
http://www.fasteddybearings.com/10-units-5x10x4-rubber-sealed-bearing-mr105-2rs/

The avids with rubber on one side and steel on the other is a bit easier to spin due to drag of only one seal. I make sure to put the seal towards the engine on the back of the bell and away from the engine on the front of the bell.

Not all bells use the same size though. I know traxxas uses larger bearings for some of theirs. I"m not sure why more don't do that... bearings with larger balls inside usually last longer.
 
I will take a dial caliper and see. The bearing should be riding on the enigne shaft right? I also might put my one speed trans on. What gear ratios do you think I should use?
 
The bearing should be on the crankshaft. There should be a tick (few thousandths) of forward/backward play once you have your bell screw tightened down.

I can't recall what I ran, but if your not on a track, it will seem really slow.
 
Ok when I had put together last there was a tiny tiny bit of play forward and backward. What kind of screw should I use for a bell screw?
 
Whatever works. I usually put a washer on it as well so the bearing race doesn't bump up against the screw. Typically a short 3mm bolt with some locktite on it.
 
Use Blue Loctite or you'll have a real hard time getting it back off is you need to.
 
I usually put a washer on there but this last time I did not. But I will next time.

I used just a bit of red and the screw came out. I don't think that it got so hot the Loctite melted because the screw still had all of it on there.
 

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