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#419244 - 02/17/12 9:09 pm T140 crankshaft in pre-unit cases  
Joined: Aug 2011
Posts: 8
john deering Offline
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john deering  Offline
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Posts: 8
Kent
Just got hold of a T140 crankshaft to go into my late p/u cases and wondered about what modifications need to be done to make it fit. What balance factor for fast road would be recommended ?
Have tried the search functions ( Honest ! ) and had no success, computers ain't my thing.

Spec is Wideline Triton, 60'Thunderbird cases, Morgo barrels and oil pump, new late 650 rods, 69' Bonnie head, Norton g/box and Commando primary cases ( hence T140 crank ).

Any help pointing me in the right direction much appreciated !

Cheers,

John.

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#419365 - 02/18/12 3:58 pm Re: T140 crankshaft in pre-unit cases [Re: john deering]  
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GrandPaul Online content
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GrandPaul  Online Content
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Laredo (South) Texas, USA
Timing side main bearing:

Buffalo Bearings # CON LS-11-2RS

(JAF # RLS-9-2RS)

No modifications to the case are required with this bearing.

Last edited by GrandPaul; 02/18/12 3:58 pm.

GrandPaul (does not use emoticons)
Author of the book "Old Bikes"
Too many bikes to list, mostly Triumph & Norton, some BSA & European
"The Iron in your blood should be Vintage"
#419375 - 02/18/12 4:32 pm Re: T140 crankshaft in pre-unit cases [Re: john deering]  
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Pete R - R.I.P. Offline
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Pete R - R.I.P.  Offline
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Vic. Australia
Buy the 3-piece 30mm double-lipped timing-side roller bearing,and grind about 0.020" off the O.D. so it fits the pre-unit case.Give it 0.0025"-0.003" interference fit.
I always replace the flywheel bolts on these cranks with grade-8 UNF bolts.1-1/2" long bolts,cut down and modified to fit,with thick hard washers.

Pre-unit engines are normally happy in a Triumph frame with 71% (dry) balance factor,and it looks like they should still be happy with that in a featherbed frame.

Norton twins often use a higher percentage,but there are two reasons:
*Their different rod/stroke ratio requires about 2.5% more balance factor than a T120.
*When you fill a Triumph crank with oil,the balance factor reduces about 2%.When you fill a Norton crank with oil it reduces more than that.Some claim only 4%,but more often they claim 10% or 11%.Still no-one uses more than 84% (dry) on a Norton,and others use less.

#419391 - 02/18/12 6:01 pm Re: T140 crankshaft in pre-unit cases [Re: Pete R - R.I.P.]  
Joined: Jan 2006
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GrandPaul Online content
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GrandPaul  Online Content
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Laredo (South) Texas, USA
Originally Posted By: Pete R
Buy the 3-piece 30mm double-lipped timing-side roller bearing,and grind about 0.020" off the O.D. so it fits the pre-unit case.Give it 0.0025"-0.003" interference fit.


Why risk a bodge-up on an incorrect bearing, when the correct direct-fit part is available very inexpensively?


GrandPaul (does not use emoticons)
Author of the book "Old Bikes"
Too many bikes to list, mostly Triumph & Norton, some BSA & European
"The Iron in your blood should be Vintage"
#419396 - 02/18/12 6:31 pm Re: T140 crankshaft in pre-unit cases [Re: GrandPaul]  
Joined: Jul 2009
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Pete R - R.I.P. Offline
In Remembrance
Pete R - R.I.P.  Offline
In Remembrance

Joined: Jul 2009
Posts: 3,549
Vic. Australia
This crank has a 30mm metric timing-side bearing ('72 onward).
There is no imperial bearing that fits this crank.

I think the bearing you listed fits a 1-1/8" crank to a small-bearing (1") crankcase.
These crankcases take the large bearing 1-1/8" x 2-13/16" x 13/16".

I'd rather grind a bearing to get a perfect fit in the housing.The housing could be less than a perfect fit on a standard bearing,because the bearings are always loose at running temperatures even at 0.003" interference cold.

The other alternatives are to grind down the mainshaft to 1-1/8" (more likely to break?),or bore out the crankcase to 72mm.If the crankcase housing wears 0.001" or 0.002" in the future,you can't then just fix it by grinding the next new bearing to fit.

#419398 - 02/18/12 6:34 pm Re: T140 crankshaft in pre-unit cases [Re: Pete R - R.I.P.]  
Joined: Jan 2006
Posts: 6,645
GrandPaul Online content
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GrandPaul  Online Content
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Joined: Jan 2006
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Laredo (South) Texas, USA
Yes, sorry about that.


GrandPaul (does not use emoticons)
Author of the book "Old Bikes"
Too many bikes to list, mostly Triumph & Norton, some BSA & European
"The Iron in your blood should be Vintage"
#419546 - 02/19/12 1:30 pm Re: T140 crankshaft in pre-unit cases [Re: john deering]  
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john deering Offline
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john deering  Offline
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Kent
Many thanks Gentlemen, I will talk to my friendly toolmaker mate and bribe him with copious amounts of beer !

#419742 - 02/20/12 12:23 pm Re: T140 crankshaft in pre-unit cases [Re: john deering]  
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Dick Harris Online content
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Dick Harris  Online Content
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East Bethany New York
Wouldn't there be a problem with the extra shaft length on the drive side for the triplex chain on a T-140?? guess you could cut it. How about it Pete?? Dick

#419766 - 02/20/12 2:39 pm Re: T140 crankshaft in pre-unit cases [Re: Dick Harris]  
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Posts: 3,549
Pete R - R.I.P. Offline
In Remembrance
Pete R - R.I.P.  Offline
In Remembrance

Joined: Jul 2009
Posts: 3,549
Vic. Australia
The Commando primary case normally contains a triplex sprocket and rotor.I think it should fit OK.
The thread on the timing-side could need trimming,to clear the bush in the timing case.


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