use a C3 or C2 roller bearing in a KH ?

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Vincent.vanGinneke
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use a C3 or C2 roller bearing in a KH ?

Postby Vincent.vanGinneke » Wed May 30, 2018 6:32 pm

The empty crankcase I have for my KH project had a Hoffmann outer ring in it.
It has 3 engraved rings that mean it was a C3 fit.
Is that normally recommended for a KH ?
I can now buy a Hoffmann but only in C2, would that be o.k. ?

DS roller bearing KH   (3).JPG

inner ring with brass cage comes from a separate crank and is a R&M item

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alan.moore
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Re: use a C3 or C2 roller bearing in a KH ?

Postby alan.moore » Wed May 30, 2018 11:04 pm

Vincent,
I asked this question some time ago reference my VH rollers and did not get a definitive reply. Hopefuly you will have better luck.

The bearing internal clearance coding goes C2 (tightest) CN (normal) then C3 (looser) . So a C2 is significantly tighter in its internal clearance than a C3.

From my investigations CN bearings do not normally have any size markings, C2 and C3 normally do.

I ended up getting my bearings from Drags and none had any size markings on them (or on the boxes) which tends to say for the VH they are CN clearance.

Cheers
Alan
1939 VH Redhunter;1942 RN WNG;1951 Triumph 6T Thunderbird;1970 BSA B175 Bantam;1986 Yamaha SRX600 single
http://cloggymoore.wix.com/triumph-pre-unit-6t

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Re: use a C3 or C2 roller bearing in a KH ?

Postby nevhunter » Thu May 31, 2018 12:21 am

Imperial bearings are getting more scarce and pricey. In a stepped roller you might have to take what you can get. The 500cc Triumph and BSA's I've worked on just use ball bearings. Probably a quality one of those would work satisfactorily. Later ball races have higher load ratings than the earlier (period) ones especially if you get the best ones. IF you have a race that has little or no play when straight out of the box , it runs the risk of being loaded when installed especially if it's tight on the shaft and in the casing. Many come loose in the case with use so I wouldn't recommend removing any from the OD. Always install using heat carefully applied to the case to preserve the interference fit as long as possible. Nev

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Re: use a C3 or C2 roller bearing in a KH ?

Postby david.anderson » Thu May 31, 2018 10:13 am

It is my understanding that any bearing that is shrunk into an alloy case should be a C3. The use of a tighter fit bearing generally results in reduced bearing life. However as we all know the cases do heat up when the engine has run so I do not see any real problems, especially with the likes of square 4 cases.
David

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Re: use a C3 or C2 roller bearing in a KH ?

Postby keith.hodgenia » Sat Jun 02, 2018 6:29 pm

I'm just thinking out loud, is there a risk with tight clearances of problems caused by flex in the crankshaft like they have with norton commandos?

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Re: use a C3 or C2 roller bearing in a KH ?

Postby john.whiting » Sun Jun 03, 2018 12:32 pm

A KH wouldnt have enough power to flex a wet noodle,let alone a forged crank...I would suggest the reason for the C3 bearing is the tight fit of the inner race on the crank.....because unlike the single,the races stay fixed in place when the cases are separated.

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Re: use a C3 or C2 roller bearing in a KH ?

Postby Vincent.vanGinneke » Mon Jun 11, 2018 8:57 am



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