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ShearedCrank
ShearedCrank
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Main bearing
#812009 06/09/20 6:51 pm
Joined: Jan 2006
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Just starting to reassemble the race motor that had an unhappy ending. With all that happened, I thought it a good idea to replace the mains.
This motor is a 71 code EE. The bearing I took out from the left drive side was a C3 condition. Last night, I heated the case, got the old race out, dropped the new CN bearing into the race and left it all to cool. This morning, I found that the bearing will spin in the race, however, it will not come out of the race as every other bearing I've had will. Too tight.
What is the proper bearing for this particular motor? And possible consequences of running it?

Thanks

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Re: Main bearing
Mike Baker #812013 06/09/20 7:28 pm
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It would be helpful if you mentioned what bike it was.
With an interference fit you need to use a C3 bearing, the housing causes the outer ring to close the clearance on the rolling elements. If you use a CN bearing it could overheat and seize


BSA B31 500 "Stargazer"
Greeves 200 "Blue Meanie"
Greeves 350
Greeves 360
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500 sprint/LSR bike "Deofol"
Jawa 500 "Llareggub"
Aprilia RSV Mille "Lo Stregone"
'35 & '36 OK Supreme
Kawasaki ZZR1400 "Kuro no senshi"
Re: Main bearing
Mike Baker #812027 06/09/20 8:18 pm
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T120

Re: Main bearing
Mike Baker #812044 06/09/20 11:57 pm
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If it's that tight, use a C3.

Re: Main bearing
Mike Baker #812082 06/10/20 10:35 am
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I kept no detail records the first time I built the motor. There had to have been a reason there was a C3 in it.
Things will be different from now on

Re: Main bearing
Mike Baker #812088 06/10/20 12:15 pm
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Simple rule of thumb, if the bearing is pressed in to the housing or shrink fitted then a C3 is required


BSA B31 500 "Stargazer"
Greeves 200 "Blue Meanie"
Greeves 350
Greeves 360
Suzuki GSX1100 EFE "Sorcerers Apprentice"
GM500 sprint/LSR bike "Deofol"
Jawa 500 "Llareggub"
Aprilia RSV Mille "Lo Stregone"
'35 & '36 OK Supreme
Kawasaki ZZR1400 "Kuro no senshi"
Re: Main bearing
Mike Baker #812104 06/10/20 3:43 pm
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I'm pretty sure that a CN was spec'd for these motors. The race is shrunk into the case.
Even though I did not keep record of it, the fact that I removed a C3 (that I installed previously) tells me that I came up against this issue 4 years ago when I initially built this motor. It must have worked well as it was one of the mechanically quietest motors I've had. The old race shows a bit of wear where the rollers ran though nothing I can feel with fingers. I'm going to have it measured to satisfy curiosity.

1 member likes this: Gordon Gray
Re: Main bearing
Mike Baker #812119 06/10/20 8:58 pm
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Originally Posted by john healy
Triumph Unit 650CC 1966-1972 Roller D.S. CN (70-2879) - RHP MRJ1 1/8-CN

Quote
Triumph Unit 650CC 1963-1965 Ball D.S. C3 (70-1591) - RHP MJ1 1/8-C3
Triumph Unit 650CC 1966-1972 Roller D.S. CN (70-2879) - RHP MRJ1 1/8-CN
Triumph Unit 750cc 1973-1976 Roller D.S. CN (70-2879) - RHP MRJ1 1/8-CN
Triumph Unit 750CC 1977-1982 Roller D.S. C2
Triumph Triple 750cc 1969-up Ball D.S. CN (70-1591) - RHP MJ1 1/8-CN
BSA Unit 500CC / 650CC 1962-1965 Ball D.S. C3 (67-1240 aka Triumph # 70-1591)
BSA Unit 500CC / 650CC 1966-1972 Roller D.S. CN (68-0625) Hoffman RM11L (Currently RHP MJ1 1/8 (Triumph #70-2879-CN) is supplied and shim cup 71-3288 should be used)

full classroom discussion here .
http://www.britbike.com/forums/ubbthreads.php?ubb=showflat&Number=711675
.


Moderated by  Allan G 

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