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Chip205
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joe a. Offline OP
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Hello All.
It has been a while since being active due to some health issues but now I'm back and trying to get the few bikes i kept back up and running properly.
I am trying to find out what type of clearance is required between quill and crankshaft end..
at this point i have approximately .090". I believe there is too much oil spilling over into timing case and possibly not enough going to cams and crank bearing along with less cooling of piston /cylinder..1953 B33
Any suggestions or help would be appreciated.

hope everyone is doing well.
Joe A.

Last edited by joe a.; 04/26/21 11:14 pm.
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Hi Joe,
Centrifugal force from the spinning crank sucks the oil from the quill up to the big end bearing so the quill does not need to be a tight fit
The distribution of oil to the cams is governed by the size of the hole in the quill
Having the crank pinion submerged in oil on start up is a good thing as once the crank spins there is a reservoir of oil in the timing case to feed the big end.
Ariel engines use a similar quill, I have seen some Ariel bikes run for years with the fragile quill broken off without doing any damage

John

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joe a. Offline OP
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Hi John,
Thanks for reply and time..
I rebuilt engine years ago without much thought since it was like that and machine was running ok...But since i had it apart to rebuild mag i questioned gap (clearances)...
I would think with less clearance there would be an advantage for cam bushings lubrication and quantity of oil to cool piston...
unless no oil is lost to larger clearances between feed quill and crankshaft?
Joe

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Originally Posted by joe a.
I would think with less clearance there would be an advantage for cam bushings lubrication and quantity of oil to cool piston...
Hi Joe,
There is a lip seal conversion that the Gold Star guys sometimes do to earlier quill fed engines (pre DB) but the crank needs to be out of the bike to do it properly.

It involves machining the timing case to accept a lip seal, pressing a stub into the end of the timing side mainshaft and then machining it Concentric and to the size that fits the lip seal. I've done it on a couple of engines during overhaul. BSA found that it significantly improved big end life on the GS engines. So, it's worth doing if the engine is already apart but I'm not sure it's worth it in your case on an assembled bike.

For a little perspective, Enfields used a quill with a cork seal on their plain bearing twins!! But I'm not suggesting any such thing partly because it always seemed to me like a shockingly bad idea but also because there isn't enough room for it in your B33.

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Hi Joe,
I believe that the centrifugal force sucks all the oil that is fed through the quill, of course it will drain back down if the engine stops at TDC

The effect of centrifugal force can easily be seen on a BSA / Triumph twin or similar bikes when an oil pressure gauge is fitted, The oil pressure gauge readings will drop with increased revs above a certain point which will frighten a lot of owners
These are my own observations after fitting gauges for testing on newly rebuilt engines

John

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“I believe that the centrifugal force sucks all the oil that is fed through the quill, of course it will drain back down if the engine stops at TDC"

I agree with the B33 or similar engine.

"The effect of centrifugal force can easily be seen on a BSA / Triumph twin or similar bikes when an oil pressure gauge is fitted, The oil pressure gauge readings will drop with increased revs above a certain point which will frighten a lot of owners
These are my own observations after fitting gauges for testing on newly rebuilt engines.”

I wouldn’t know whether this happens on BSA’s but it certainly doesn’t happen on Triumphs. I’ve had a pressure gauge fitted since ~ 1982 on p/u Triumph 650.

If you think about it, for that to happen, the escape flow would have to increase dramatically as rpm rises, beyond the corresponding rise in pump flow.

If such a situation were to arise, it could only be through excess big end clearance (in a B-range Triumph.)

C-range Triumphs with the pre-69 timing side bush and BSA’s may behave differently.


Moderated by  Allan G, Jon W. Whitley 

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