Excessive Endplay

[scrub_74]

I have just replaced the pistons/cylinders and heads on my 1600 DP. The case, crank and connecting rods looked fine. I cannot set the endplay of the flywheel to less than 0.050 inch. If I increase the shims, the flywheel locks up. So, the end play is either 0.050 with three shims, or no end play at all if I try to reduce it. Looking for clues to solve the problem.

[Glenn]

Increase how?

Add a 4th or use 3 larger shims?

[scrub_74]

I am trying to keep to the 3-shim approach. If I increase one of the three shims to try to reduce the 0.050 end play then the whole crank/flywheel will not turn. Even if I try to use 4 thinner shims to increase the overall shim thickness to reduce the end play then the crank/flywheel will not turn. Going back to the 3 shims I started with that allowed 0.050 end play will allow the flywheel to turn, and the end play is 0.050 again. There seems to be no logic in my results.

I forget what the end play of the flywheel was before shims were added. I was suspecting that the main bearing was turning in the case,or not seated somehow, and the end play process was getting fouled up. I am pretty sure the rear main seal is seated well and not protruding past the case surface around it. I definitely do not want to tear down the motor and open the case.

Can I machine the flywheel on the surface that mates up with the crankshaft? Also, what will happen if the end play is way past the 0.004 spec?

[Marc]

It appears that the majority of the measured endplay is not between the flywheel and the thrust bearing, but between the bearing and the case. If so, there's no proper repair that can be made without a complete teardown to machine the case for a thrust bearing with a thicker flange.

With the flywheel and shims off, hold your fingertips across the periphery of the thrust bearing flange while an assistant clunks the crankshaft to & fro from the pulley end. ANY motion of the bearing relative to the case is unacceptable.

Another thing that can cause random endplay measurements is a crank with a slice cut into its nose (from running with early endplay shims that have a 1mm larger I.D. than the late ones - they sling about like a hula-hoop and cut right through the crankshaft until they hit the harder dowel pins). The shims tend to catch on/drop into the slice, causing inconsistent readings.

If the thrust bearing is loose as I suspect, all you can do short of an overhaul is to peen its flange towards the case to snug things up - the looser it is, the looser it gets; this may buy you a few thousand extra miles. If you can find one, there's a motorcycle oil scraper ring that can be spiralled into the gap between case and bearing if it's greater than ~.025"....very sleazy, but I've used it to keep engines on the road for several months while looking for a replacement.

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[scrub_74]

Thanks for your earlier posts on end play issues, and on my post as well. You are correct - there is something fouled up with at least the thrust bearing. I get axial play in the bearing relative to the case when I removed the flywheel and pushed/pulled the pulley end. That is the source of the problem I have. I will be digging into the short block to rebuild it. You mentioned in your response that I can put in a fresh thrust bearing with a thicker flange to eliminate the axial play. Are thrust bearings available with various flange thicknesses?

Bummed, but at least on the right track now....

[ONEBADBUG]

If you can find one, there's a motorcycle oil scraper ring that can be spiralled into the gap between case and bearing if it's greater than ~.025"....very sleazy, but I've used it to keep engines on the road for several months while looking for a replacement.

The old metal "Slinky" fits perfect, not that I would know anything about such a practice.

[Marc]

...Are thrust bearings available with various flange thicknesses?...

In 0.5 and 1.0mm (.020/.040") O.D., you can get thrust bearings with standard width flanges or with the flywheel side 1.0mm thicker. Larger bores come in 1.0mm and 2.0mm "oversize" (the latter's box will typically be marked "OST+2")....at least that's the way it was 20-odd years ago when I was still actively building engines.
I've always subscribed to the idea of cutting no more from the case than is necessary to make a thrust bearing fit (unless it's a trashmo that for other reasons will never be rebuilt again anyway) - the more "meat" left in the case, the more potential lifetimes remain. I prefer to just cut the case's thrust surface far enough to clean it up, and then trim the flange of an "oversize-thrust" bearing on the lathe until it's a good fit.

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