Forum

[ChrisD]

Hi all.
I am rebuilding my 1996 500 classic ready for the next long trip (CT-UK) and am fitting new mains, roller bigend, GB sealed bearings, bushes etc and I also need to replace the timing chest gasket. Our hosts sell two thicknesses, ~28thou and ~35thou. How much they will compress over time?

There’s the correct 5 thou gap between cam faces and timing chest cover (from Plastiguage) so I’ll need to add the gasket amount, and the idlers have ~20 and 24 thou spacing so I’ll have to add thicker shims there. I also have to cure the offset of one idler by ~40thou (the supplied shims are nearly 2mm so they are too thick to adjust that out). But I don’t know how much the gasket compresses, so I don’t know how thick to make them. I thought I’d do this in advance and have a selection made (if I don’t use them now they’ll be great for the Redditch 350) but the local cost is horrendous.

Our host don’t sell a set of shims for these shafts, so I’ll need to make some. Can I punch them out of aluminium instead of having to use steel? After all, the casing is aluminium.
I’d welcome your comments.
Cheers, ChrisD

[andy w]

Hi Chris.I have bought shims from our hosts for the camshafts,about 5 thou each.This was a few years ago and was to stop the clatter of the shafts.I think the rotation of the cams against the followers leads to some side thrust.I have a few shims on each cam,it is all to do with gasket thickness.I can look back and see if I have a part number if you like.Andy.

[Norm]

Hi Chris, Which shims are you talking about, if it is the shims on the cams then the sprag clutch shims will fit, must be millions of those sitting in sheds by now

[ChrisD]

Gentlemen
Thanks for the quick input. Yes Andy, cam shims are available but they are as you say 5thou. I'd need to use a lot to fill the gap of ~25-30thou and even more for the idlers.
That sprag clutch shims would also fit is really interesting and I'll follow up - thanks Norm. I was quoted a price of ~R80 each or some GBP4 apiece to make to my sizes in stainless steel! I also seek shims for the idlers and to correct the offset nature, need at least 1-2 at ~40 thou.
Can I use aluminium or should I stick to steel?
Cheers
ChrisD

[simon]

I've made several shims for the Ducati by parting them off on the lathe. If you have access to one this is quite a good method for bespoke shims.

[Norm]

Chris, from the spare parts catalogue the idler gears shims are part number 140121 and you need 4 of them and the cam shim is 112078.Don't try doing your head too much about them, main thing is making sure they aren't too tight against the timing cover