Drive Side Bearing Setup Question Series ‘A’

billirwinnz

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I can't find a spring to fit between the bearing inners. Does anyone have a spare or a source?

In the absence of a spring is there any reason I can't fit an outer sealed ball bearing and a plain (non-lipped) inner roller with a spacer between them with both bearing outers retained by loctite? The shaft is held axially by the timing side and the shafts are a sliding fit in the bearing inners so free to move with expanding cases.
 

BigEd

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Not sure what you mean by "In the absence of a spring ". Do you mean the ET125 circlip?
When the engine sprocket nut is tightened up the crank is pulled up to the drive side bearing. The bearings should be a light interference fit on the shafts.
 

Simon Dinsdale

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BigEd, Bill is asking about series A which is a completely different design with a spring between the two bearings on the drive side main shaft.

Bill, my understanding is on series A the crank is secured / located on the timing side and everything floats on the primary side. The spring is there to ensure the outer drive side bearing is pushed tight against the outer shims and shields to ensure the small clearance determined by the shims is maintained. With no spring the outer bearing could move and the shim and shield clearance alter and so could cause the primary to fill up with engine oil. The purpose off all those shims and shields on the drive side is to form a sort of oil seal between the engine and the primary.

Simon
 

Simon Dinsdale

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Have you tried something like a post war valve spring cut down in length to suit?
I don't think the spring pressure is a critical figure.
Simon
 

Bill Thomas

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Peter thinks this is for a Twin, I have been looking at it for about 40 years, Trying to think where it goes,
Brother Ron must have left it when he left home !, I let Peter have this one. Cheers Bill.
 

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billirwinnz

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BigEd, Bill is asking about series A which is a completely different design with a spring between the two bearings on the drive side main shaft.

Bill, my understanding is on series A the crank is secured / located on the timing side and everything floats on the primary side. The spring is there to ensure the outer drive side bearing is pushed tight against the outer shims and shields to ensure the small clearance determined by the shims is maintained. With no spring the outer bearing could move and the shim and shield clearance alter and so could cause the primary to fill up with engine oil. The purpose off all those shims and shields on the drive side is to form a sort of oil seal between the engine and the primary.

Simon
Hi Simon

My understanding of the purpose of the spring is the same as yours. With a sealed outer bearing it is redundant. I've often wondered why PEI didn't fit two roller bearings on the drive side. Perhaps cost? A ball was good enough.

Cheers Bill
 

BigEd

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BigEd, Bill is asking about series A which is a completely different design with a spring between the two bearings on the drive side main shaft.

Simon
Dear Simon,
Thanks for that. I hadn't looked closely enough at the thread title.:oops:
 

Simon Dinsdale

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Hi Simon

My understanding of the purpose of the spring is the same as yours. With a sealed outer bearing it is redundant. I've often wondered why PEI didn't fit two roller bearings on the drive side. Perhaps cost? A ball was good enough.

Cheers Bill
Bill
I'm not sure a sealed bearing will stop the pressure in the crankcases from blowing oil into the primary. Usually the seals on a sealed bearing are to keep the lubrication the manufacturer put inside the bearing. I know owners have used sealed bearing on post war bikes but that still has the scroll seal to get past first.
Simon
 

Bikerjoan

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Bill,
heres a photo of the one that was in my Comet, Im assuming it is correct & looks like a big thackeray washer. Maybe others can confirm if its correct ?

Jon
 

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Robert Watson

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That is the one.

I converted all the shafts and bearings on both my A's ( I use the word I quite loosely) to post war style. That left me the two springs on the shelf. I have already given one away and I understand they are very much made of unobtanium at the moment. I am not sure what the Aussie boys did in there and if they kept the original setup.
 
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