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Buell Motorcycle Forum » XBoard » Buell XBoard Archives » Archive through January 04, 2008 » Question on the '08 crankshaft bearings « Previous Next »

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Harryd
Posted on Tuesday, December 25, 2007 - 08:12 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I did not see a catagory in the Knowledge Vault for this question, so I will ask it here.
I read Al's very informative account of the '08 cam setup where the cams run in the aluminum case instead of bushings (plain bearings?) as earlier, although with much improved oiling from the new oil pump design with ~12 psi. more pressure.
My question is regarding the main bearings on the new stronger crankshaft, are they now plain bearings instead of the previous roller bearings?
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Ducxl
Posted on Tuesday, December 25, 2007 - 09:49 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Definately NOT PLAIN bearings.Not fact but.....well,definately NOT plain.I think it isn't possible,but the reasoning escapes me right now.But i believe it's related to the fact that they're air-cooled.

And plain bearings are superior to rollers
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Billybob
Posted on Tuesday, December 25, 2007 - 11:17 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

where is Als' thread on the 08 cam set up
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Harryd
Posted on Wednesday, December 26, 2007 - 08:51 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I am not convinced that roller bearings are "absolutely necessary" in the Buell motor, especially with the new oil pump design. If the pump has the necessary pressure and volume to lubricate plain bearings, than plain bearings would allow a stronger 1-piece crankshaft instead of the pressed-together design.

Al has some comments on the '08 cam bearings and new oil pump design in the following thread:
http://www.badweatherbikers.com/buell/messages/384 2/313029.html?1192906064
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Mcgiver
Posted on Sunday, December 30, 2007 - 02:59 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

A plain bearing crank would need side by side rods instead of the knife & fork arrangement. This would develop a rocking couple balancing problem that our current engines and isolation system cannot handle.(I think) Brian
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Harryd
Posted on Sunday, December 30, 2007 - 03:43 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Thanks, Mcgiver
That does make sense, as it would take some pretty creative engineering to cap the ends of the current type rods with a non-offset (side-to-side) cylinder layout in the current design.
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Blake
Posted on Sunday, December 30, 2007 - 07:13 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I don't see why knife and fork couldn't work with journal bearings too. The width required would be the issue. The roller bearing configuration can be much narrower.
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