crank shim issue

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Scottish888
Posts: 266
Joined: Wed Feb 07, 2018 1:47 am
Location: Edinburgh, Scotland UK

crank shim issue

Postby Scottish888 » Wed Jun 19, 2019 11:38 pm

Today, tried to fit my newly rebuilt crank and shim correctly into cases with all new bearings but had some issues I expect could be due to my lack of experience with these engines.
First checked the crankcases fitted well together with just the new crankcase oiled gasket fitted, no problem, tight and aligned.Fitted a non shimmed crank, all good.
The new gasket is a little thicker than the old so I expected the old shims would not be enough but fitted the old shims in the case halves they came from, one each side. 0.53mm on LHS and 0.32mm on RHS.
The crankcase would not close together, it was pivoting around the crank leaving the case to rock a little, removed one (thickest) shim, better but still rocking a bit.
Removed all shims, kept crank in, case closes perfectly. Measured the end float at 1mm so all my shims should have fitted fime still leaving a little too much end float.
Put the 0.32mm shim on LHS, slowy and by hand tightened the case to close the case gap to see if the crank locked up...it did.
Tried the shim on the RHS, case fitted a little better but not much but it gave the same result, nipping up the crank if try to tighten the case.
I know not to use the case bolts to force it together but this was a test.
Stuck now, got 1mm end float with no shims but cases close perfectly and crank spins easily, put a 0.32mm shim in and the case wont fit square and will lock the crank if slowly tightened.
Bearings are all flush to rear of housings
Any suggestions will be most appreciated.

double diamond
Posts: 555
Joined: Thu Apr 28, 2011 1:20 am

Re: crank shim issue

Postby double diamond » Sat Jul 06, 2019 1:21 pm

Sounds like the shins you’re using are too tight a fit on the pinions. There is a radius where the pinion joins the flywheel. The shins have to clear the radius either by a bevel on the shim or enough inside diameter to clear the radius.

Matt

ranton_rambler
Posts: 439
Joined: Sun Jun 04, 2017 11:33 am
Location: Stafford UK

Re: crank shim issue

Postby ranton_rambler » Sat Jul 06, 2019 3:03 pm

Don’t the shims all go on the same side? Will need to check my notes to see what I did.
What I can remember is that apparent endfloat does not exactly relate to the shim thickness to adjust. I guess there is a little bit of distortion when everything is tightened down.

double diamond
Posts: 555
Joined: Thu Apr 28, 2011 1:20 am

Re: crank shim issue

Postby double diamond » Mon Jul 08, 2019 12:49 am

I’ve typically found all the shims to be on the left side since the left is the case half that would be lifted to replace the shims. But shims can be located on either side in an effort to center the connecting rod.

Matt


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