Crank and thrust bearing holes not lining up.

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John Holmberg
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Location: SC

Crank and thrust bearing holes not lining up.

#1 Post by John Holmberg »

I am starting the rebuild of S90 engine #800295 since it developed a rod nock. The engine is now totally dis-assembled. I decided not to reuse the S90 crankshaft and bought a new crankshaft and main bearing set from NLA/Stoddard. The thrust bearing is a one piece bearing and fits properly in the engine case with the oil supply hole and notch properly aligned. However when I slide the bearing on the crankshaft the bearing oil hole and the crankshaft oil holes do not line up perfectly in the direction of the centerline of the crankshaft. The bearing is up flush to the crankshaft throw and the end play shim will go between the bearing and the flywheel. They overlap each other by about one third of their diameters. The bearing hole is closer to the flywheel and the crankshaft holes are closer to the crank throw. My concern is will the crank shaft journal and the rod journal it supplies receive enough oil? I think that it is OK as it is, but I am by no means an expert on the subject. Any advice will be appreciated.

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Vic Skirmants
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Re: Crank and thrust bearing holes not lining up.

#2 Post by Vic Skirmants »

John; I just examined a couple of cranks and main bearings. On a stock crank, the holes line up; on an old SCAT, they are off slightly. Without seeing your particular set-up, I probably wouldn't worry about it.

John Holmberg
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Joined: Thu Oct 21, 2010 9:24 am
Location: SC

Re: Crank and thrust bearing holes not lining up.

#3 Post by John Holmberg »

Vic. Thanks for the reply. The subject crank is an aftermarket one purchased from NLA. I also took the crank and the new bearing to a local engine builder who does BMW motorcycle air heads. After looking at it he thought that it would be OK but told me to get another opinion. Thank you for taking the time to look at some crankshafts.

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Wes Bender
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Re: Crank and thrust bearing holes not lining up.

#4 Post by Wes Bender »

Any thought of possibly enlarging the hole in the bearing slightly, say with a chain saw file? I'm with Vic though. Probably OK to use the way it is. Once you've pumped up the oil pressure a bit before starting it for the first time, there isn't a huge flow through there.
Some days it's just not worth chewing through the restraints.....

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