BiMetal Bearing

[SoloFrenos]

Having stripped down my new motor i have found that the bimetal bearing has seen better days. Can anyone tell me how i remove and replace the white metal bearing from the 'holder' as i'd rather not replace the whole thing simply on a cost basis. Also on the bearing front, is it a worthwhile upgrade to replace the oil pump side crank bearing with a roller type rather than the standard ball bearing, the engine is not tuned (just a 375cc top end) and i'm not a fast rider. Thanks

[George 350]

Hi Solo,
Bearing removal/ installing: Please don't try with anything other than a press, for no other reason than that is the only way to guarantee it will go in square. A local engineering shop should do it for you for next to nothing. If you try to fit them in with a Birmingham screwdriver and a suitably sized drift, you will almost certainly distort the bearing shell and probably permanently damage it. It doesn't need a high pressure, it is simply the ability to push it in squarely and in a controlled manner that is needed.
Re: Going the crank grind and roller route, I looked at this a few years ago when my Sport's (at that time had been standing 10 years) bearing 'picked up' and wrecked itself and the generator stator. I chose to stick with the plain bearing. It had done 93,000 miles up to that point, so there isn't a lot wrong with the plain bearing design.
If you are, as you say a steady rider, I would stick with the plain bearing, as it is a lot less hassle.

George.

[SoloFrenos]

Hi George, thanks for your reply. My local engineer is very friendly so i'll pop down and use his press (and expertise). I assume then i just press out the old one too?

Again thanks for the advise on changing the bearing I think i will leave the plain bearing as it seems alot of extra work for not much gain (on my bike). Would it be worthwhile upgrading the bearing the other end of the crank to a parallel roller rather then the standard ball, i assume that would be a straight swop? Or should i again just stick with the standard set up?

Many thanks, Tony

[George 350]

Hi,

You must keep the ball race there as it provides the axial location for the crank. Without it, the helical primary gears would push the crank against the right hand side of the crankcase with disasterous consequences.

george.

[EVguru]

Replacing the drive side ball race with a roller would would mean there was no bearing capable of taking thrust loads and you'd wreck the engine.

The 'weak' bearing is the timing side plain bearing which was introduced to solve high milleage reliability problems with the original ball race/sliding sleeve arangement. I run my bike well past the red line each year at Cadwell with the plain bearing, so particularly in the 350 engine, it's not particularly weak.

If the plain bearing journal on the crank is within limits for size, concentricity and parallelism, them by all means simply fit a new shell bearing. If the crank needs to be ground anyway, that's the point at which you might consider a conversion to a timing side roller bearing. There's no real need to except on a high revving tuned 350.

The balance changes a bit for the 500 with its longer stroke and higher crank loadings. Here the drive side bearing was upgraded, to an FPAC (four point angular contact). Most of the gain is in thrust loading, but the construction also allows for more/larger balls and a significant increase in radial load capability. I think Morini never tuned the 500 engine to even the extent of the 350 Strada because of the timing side plain bearing and an upgrade here is a good idea if you want to push the engine any harder.