Author Topic: B31 crank shaft  (Read 283 times)

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DEDGE

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B31 crank shaft
« on: 15 February, 2018, 19:08:20 »
Hi All
More help needed with my 1950 b31 renovation.
I have split the crank case, the big end seems ok but I intend to change the main bearings. There is a ball race and a lipped roller race on the drive side and a lipped roller race on the timing gear side.
Should I replace the lipped races with the same or use plain ones.
Wat’s the advantages and disadvantages of using lipped ones.
Why were lipped one fitted in the first place.
What way round should the lip go.
All the Best
Dedge

JulianS

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Re: B31 crank shaft
« Reply #1 on: 15 February, 2018, 19:41:22 »
The ball bearing locates the crankshaft.

The roller bearings have a high load capacity, lipped rollers bearings were fitted as original equipment. The lip goes on the outside, makes it easier to dismantle the bottom end, the timing side should just fit off leaving the outer in the case and the inner on the shaft.

On the other side the ball bearing and roller outer will stay in the case and again the inner will stay on the shaft.

Stick with what BSA intended, it would present considerably more problems reassembling the bottom end if you changed to a non lipped bearing.

DEDGE

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Re: B31 crank shaft
« Reply #2 on: 17 February, 2018, 16:18:00 »
Hi All
This might be a silly question, but now I have flywheel & conrod unit out what's the best way to clean it all before I fit the new bearing'
All the best
Dedge

Thanks for the bearing info Julian

DEDGE

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Re: B31 crank shaft
« Reply #3 on: 17 February, 2018, 17:31:20 »
Re above I am only fitting new crank shaft bearings not the big end

ANDY HIGHAM

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Re: B31 crank shaft
« Reply #4 on: 17 February, 2018, 22:26:27 »
it would be folly not to put a new rod and big end in it while it's apart. A leg out of bed can be expensive