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Thread Like Summary
drunkenmonkz, leon bee, Nick H
Total Likes: 5
Original Post (Thread Starter)
#831524 11/30/2020 3:09 AM
by drunkenmonkz
Hey all,
On my 64 thunderbolt motor I'm about to start assembling, the parts diagram shows a shim cup, part 68-0168, that looks like it goes between the crank and whatever shim/shims needed for end float then crank bearing then inserted into case. Is this correct? I don't have a shim cup in my pile of parts. There's someone that has the part listed on ebay and the picture looks to me like the lip of the shim cup would hit/rub on the bearing - protruding past the actual shim.
Am I painting a clear picture?
Am I missing something?
The shim cup rides against the crank...?
Doesn't seem correct...
Liked Replies
#831692 Dec 1st a 02:50 AM
by Nick H
Nick H
I went with the roller bearing. I had 2 shim cups, and early and a late version. As I recall neither fit my KLH bearing.
I ended up buying shims from McMaster Carr that were a close fit to the crank size. No shim cup.
Then discovered the fillet on the crank so had to enlarge the ID of the shims. As I recall...
1 member likes this
#831744 Dec 1st a 04:47 PM
by Allan G
Allan G
Be worth adding that if your using a ball race you do the check without the mentioned sprocket/rotor etc fitted otherwise you won’t be able to feel the end play.

If your using a roller, fit the sprocket etc and tighten it up that way you will be feeling all available end float
1 member likes this
#831725 Dec 1st a 01:58 PM
by MarcB
Originally Posted by drunkenmonkz
Cool. Hopefully the new bearing fits with the shim cup I'm purchasing off eBay!
I've rebuilt a later (68) so am familiar with the end play setup. How do you set running clearance on the earlier ball bearing setup?

"Running clearance" simply means that there will be enough space in the case to spin the crank freely once warmed up. The goal here is to ensure there is some space on the right side of the crank, between it and the lip on the timing-side bush.

It doesn't have to be much, probably .003" (about the same as the endplay set with the roller bearing). With the cases bolted together, I aim for no rubbing when installed dry. Obviously, this is from experience so may require a number of test fits to get it right. You need to "hear" with your hands as much as with your ears. Installing the sprocket, rotor, and nut will only increase this space so I've found this to be a good setup.
1 member likes this
#832459 Dec 7th a 12:19 AM
by drunkenmonkz
Originally Posted by NickL
A lot, probably most of the engines i've built have been a mixture of parts.
IE, early cranks into later cases etc etc. The only correct way of doing the
job is to measure it. It's close enough to use the flywheel as the guide, just
measure the width and halve it, mark a line around it, then put a piece of
shim into the joint faces of the cases and line that up.with the mark. That
will then allow you to move the crank back and forth with a clock on one end.
Thus establishing the shim size.

It's not that critical but makes for a sweeter engine if all is lined up. Doing the
job with mixed parts can be a little more complicated. With the later cranks
and roller setup you have to setup for minimal end float or make up TS thrust
washers etc. If all your parts line up with the book, just follow the instructions there.

The crank and cases are from the same motor. Connecting rods are new cromoly from map cycles, srm oil pump and newby clutch/belt drive. The head and cylinders are from other years/models. The cylinders I'm using were in better shape than the ones original to the motor and I'm putting a thunderbolt head on instead of the lightning. all those things shouldn't be an issue now though (I'm sure will be later...)
I rebuilt the 68 motor in my bike now almost ten years ago and it ran solid for many thousand miles (until return oil line popped off on my way to work this spring)
I may seem dense and repetitive in my questions, sorry for that, I just want to make sure this motor will be as solid as an a65 can be. And that I'm understanding things absolutely correct.
all the tips, tricks and ideas for building it are greatly appreciated!!!
1 member likes this
#832465 Dec 7th a 01:36 AM
by drunkenmonkz
Rhp c3 main bearing. Seemed like the best option. That I know of anyways. Something better in your opinion? Also a friend of mine is a fantastic machinist so we bolted the cases together, had them blocked on the mill bed, trammed in the head to be inline with the cases, removed the left side case then bored the bush to fit the crank. I think we got it to .0005 or .0008 or something like that. I can't remember what the tolerance call out was but it was as close as we could get.
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