Washer between the main bearings on HW singles

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LynP
Member
Posts: 335
Joined: Mon Jan 01, 1990 12:00 am
Location: GWENT UK

Washer between the main bearings on HW singles

Post by LynP »

Please could anyone enlighten me as to the function of the large washer that fits between the two deep grove bearings on the drive side of HW singles? I was told by a bearing supplier that it would be to do with spacing the bearings, while I could understand his reasoning I felt there would be more to it as there are various part numbers for this washer. Is it for example to restrict the amount of oil reaching the outer bearing and so lessen the over spill into the primary chaincase? and what are the difference between the various washers used and why?

Thanks, LynP
Braaap
Posts: 75
Joined: Mon Jul 09, 2018 10:24 pm
Location: New Zealand

Re: Washer between the main bearings on HW singles

Post by Braaap »

Hi.
My best guess is: The large washer is nearly big enough to contact the outer race of the bearing it is up against, forming a partial seal.
Remembering that there were no modern lip seals when the bikes were made.
(Witness the sealing method on the camshaft extension which has the mag drive sprocket on it... a spiralled groove in the bush).
I LOVE that technology.... and abhor the fitting of lip seals.
Let the next generation see how it was made!

Using 2 seperate washers will reduce any wear caused by the bearings moving relative to each other... as they may do, with the cush driven sprocket working against the outer bearings' inner race.
Braaap
Posts: 75
Joined: Mon Jul 09, 2018 10:24 pm
Location: New Zealand

Re: Washer between the main bearings on HW singles

Post by Braaap »

I read an old thread from this forum re "the bearings going tight as the casing cooled after instalation.

Some folk suggested a C4 bearing may be needed..
or perhaps they were faulty bearings?

The fact is... as the cases shrink radially and grip the bearing outer races, they also contract axially and crush the inner races against the spacer washers.

The trick is: insert a 3 legged piece of paper in the assembly (between a bearing inner race and a spacer) when u put the bearings in the heated case.... as it cools the outer races will be gripped first... then PROMPTLY remove the paper by pushing the center piece thru...

As the assembly cools and contracts more the inner races will come into perfect light contact.

Some experimentation may be needed to get the right thickness paper.

(Paper drawn in white... bearing INNER race yellow )
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LynP
Member
Posts: 335
Joined: Mon Jan 01, 1990 12:00 am
Location: GWENT UK

Re: Washer between the main bearings on HW singles

Post by LynP »

Thank you Braaap, we both seem to both think the Washer between the bearings is to restrict oil going outwards. When I fitted the main bearings in my last set of cases I did as my manual said and heated the case and just dropped drop them in using an old shaft to ensure they were lined up, I did not tap them down. However, as you say they did tighten against each other as the cases cooled. The information I have is that the factory specified a C3 fit for the outer smaller bearing which I used, so I assume this was to allow for this cooling effect. When I fit a set into another pair of cases I have I will try your paper trick.
My last question was as to why different washers were used between the bearings, were some thicker/thinner or different diameters. Part numbers for these washers are 010628 Skefko and 021859 1958 on.

LynP
Braaap
Posts: 75
Joined: Mon Jul 09, 2018 10:24 pm
Location: New Zealand

Re: Washer between the main bearings on HW singles

Post by Braaap »

The later engines have a single spacer, (no cush drive).
The early engines have two spacers, (and a cush drive on the engine sprocket). Presumably to reduce wear from the bearing inner races moving.

The outer bearing is a c3 because it is a tighter fit in the cases. The inner bearing is less tight, presumably to allow it to find its own position in service, while the outer bearing remains fixed to control crankshaft end float.
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Last edited by Braaap on Thu Oct 18, 2018 11:33 pm, edited 1 time in total.
LynP
Member
Posts: 335
Joined: Mon Jan 01, 1990 12:00 am
Location: GWENT UK

Re: Washer between the main bearings on HW singles

Post by LynP »

Thank you again Braaap, the pictures explain the set ups clearly, I did not know about the differences in the interference fits.
LynP
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