thedktor Posted November 28, 2012 Report Share Posted November 28, 2012 (edited) Not been on here a while, but some may remember my trials and tribulations trying to get this old bike back up and running: http://www.trialscen...-gears-damaged/ http://www.trialscen...y-gear-removal/ http://www.trialscen...9-crank-damage/ …and some more… Anyway, the engine is ON THE BENCH with a genuine intention to put all the many bits back together, and I can’t recall where these things go: Well, I’m pretty sure they go between the main bearings and the crankshaft seal carriers, can anyone confirm? And if so, why??! But what puzzles me is that there at least two different thicknesses of these shim things and I’ve no idea what I’m “shimming”. Note that the picture is all the shims from two engines….. Thanks for any pointers - Steve Edited November 28, 2012 by andy Fixed broken embedded image Quote Link to comment Share on other sites More sharing options...
feetupfun Posted November 28, 2012 Report Share Posted November 28, 2012 yes that is where they go, and they are to locate the crankshaft in the right place. You will need to understand shimming to put that motor together without damaging it Quote Link to comment Share on other sites More sharing options...
thedktor Posted December 1, 2012 Author Report Share Posted December 1, 2012 (edited) OK…. So any clues then?! I have rebuilt quite a few engines but none have this shimming method. Here’s where the shims go: So looks like they hold the main bearings to prevent any creep sideways/outwards as the engine temperature cycles. Which would suggest…. That the crank bearings need to be fitted with zero clearance against the crank. Or??? Edited December 1, 2012 by thedktor Quote Link to comment Share on other sites More sharing options...
feetupfun Posted December 1, 2012 Report Share Posted December 1, 2012 yes the bearing inners rest against the crankwheels on both sides. The shims are to hold the crankshaft in the right spot so the conrod runs in the middle of the crank pin. Be careful you don't bend the crankshaft during assembly of the bottom end. This is a common mistake whe rebuilding motors that have a crank that can be adjusted side to side and it causes the primary drive gear teeth to bind at the tight spot. I suggest that once you get the crank in the middle, you make sure it is straight before deciding what shims to fit for final assembly. The motor was made to use 0.5mm thickness gasket material for the crank seal carriers and the centre gasket. Quote Link to comment Share on other sites More sharing options...
thedktor Posted December 4, 2012 Author Report Share Posted December 4, 2012 OK thanks feetup. Any tips for how to actually do this then as obviously the bearings are not free to float so will need some "persuasion" to move and find the right position. Cheers, Steve Quote Link to comment Share on other sites More sharing options...
feetupfun Posted December 4, 2012 Report Share Posted December 4, 2012 fit the bearings to the crankshaft first by heating the bearings. When the crank is cool (some people put it in the freezer to get it nice and cold) heat the casings to fit each side, one at a time. That will minimise the side loading on the crankshaft. If there is too much resistance when the bearing outers are being fitted into the cases, pull them into place with a puller rather than pushing on the other end of the crank. Work out the positions for where you want the bearings to go before you start, so the bearings end up at the right spot in the casings. Once you have worked out the position, you can use the seal carrier as the stop for how far to insert the bearing. One way to do this is to use the old gasket and the chosen shims. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.