"New" CB crank main bearing journal size

[Mike Cott]

Hi guys
Started to mock up an engine I'm planning for my rail

I've a new Cb 76mm forged crank, what id  bearings size should they be?
I've bought silver line  steel back STD size and boy are they tight, so much so I don't want to force them on without getting some advice off you guys first.

Ta Mike

[Martin S.]

You should mic the journals to see what they measure. Too tight is not good. When my engine was built, the bearings were plastigauged and then clearanced using paper towel and WD40. It took an hour of rubbing by hand per thou of clearance. The idea is to get oil flowing thru the bearing.

[Mike Cott]

I think I've settled on the bearings being supplied incorrect, going to see what another set fit like first

[jay c]

I had a problem with silver line bearings. The little tangs didn't sit in the case properly making them too tight on the crank. Changed to kolbenschmidt bearings and it was all good

[Martin S.]

I believe bearings that have tangs on them are the cam bearings and the rod bearings, not the crank bearings.
The other thing you can try is an old set of bearings that came out of an ok motor and try those and see how they fit the crank. Also you can test the new bearings swapping them out one at a time in combination with a known good used set. That's what I did when I had a tight bearing problem. No measuring!

[Mike Cott]

Good idea Martin. I hadn't thought of that I'll dig out my old crank and bearings if I have them and try Them 

[Mike Cott]

Supplied the wrong bearings in the wrong box, sent the correct Ines and all is well


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