So continuing from where I left on the fall. I had new bearings in the cases and I needed to determine the required shimms for the crankshaft to obtain the desired preload. The shims were 2,25 mm on the chain(LH) side and 2,15 mm on the clutch(RH) side. But the mains went bad so it made me wonder what's wrong. I actually measured the end float on the fall and came in to conclusion that the preload was actually correct. But I still decided to take a second look now as I'm continuing the project. Found out something new I hadn't noticed before: crankshaft's oilway plug was loose and its thread prevents crankshaft's shimm to align nicely. It actually causes inequal load to the bearing so this could actually be the reason why the main bearing looked like it did. Here is a picture:
I went through my older photos and noticed it's loose in there too. I swear I didn't untighten it and the photos confirm that. The plug even had some scratch marks on it. The shim itself was just polished compared to the one on the other side. Anyway the plug should have thread locker and it should be tightened to fully home. It didn't seem to have anything extra in the thread. It's tight now and thread locked so probably not an issue anymore.
Next the actual measurement. There are two methods in the Workshop manual: the first one is to measure the depth of both cases and the thickness of the crank from web to web and add the preload. I had my doubts because while this should be perfectly good method to measure it requires more precise tools that are on my disposal. So I decided to try out what kind of numbers I'll get using a level and a digital caliper:
The crank isn't any issue since it gives quite consistent readings. The case is a different story. The level is pretty much the best straight item I have but doesn't seem to be good enough. The idea is to measure the distance between the contact surface on the case and the bearing. The readings I got varied for about 0,15mm to 0,20mm so that's way too inaccurate. I didn't even threw out the notes of the measurements but at least I know I can't do it this way. There's one thing this method revealed though: LH side is a little bit wider than the RH side. That may be the reason why the original shims aren't equal size.
The easier way is to get thinnest shims there is and put the crankshaft in and close the cases and tightened the screws to specified torque. So I got a pair of 1,90 mm ones (damn 25€ each) and measured the end float with dial gauge:
Even with this setup the numbers aren't obvious to me. They probably are for someone who has more experience but there's always the first time. So I had the dial gauge at the end of the crankshaft. Then I rotated the crank for a few rounds and the dial still pointed zero, so all good. The book says to use a screwdriver to level the crank up but I found the readings to have more variation that way so I just grabbed the crank with hands from the top and pushed from the botton, and got pretty much only 0,01 mm differences. I came in to conclusion the end float with 1,90 mm shims is 0,25 mm.
I have two versions of Workshop manuals: 2001 and 2002. The newer one suggests a preload of 0,30 mm and the older one 0,15 mm ± 0,20 mm. I think I'm gonna trust a bit more to the newer one of 0,30 mm. It also fits to the older specification which goes up to 0,35 mm preload. So my case:
1,90 mm + 1,90 mm + 0,30 mm (preload) + 0,25 mm (measured end float) = 4,35mm
So I need 4,35 mm of total shimming. What I had was 2,25 mm + 2,15 mm = 4,40 mm. This means a preload of 0,35 mm which may or may not be a bit too tight. It's in older spec but I kind of would like to avoid the limits of the range so I ended up ordering one 2,20mm shim for the LH side. While I wait for the shim to arrive, I can do the valves.
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