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#394168 - 09/12/11 8:10 pm Pre unit Triton, Unit crank ?  
Joined: Aug 2011
Posts: 8
john deering Offline
BritBike Forum member
john deering  Offline
BritBike Forum member

Joined: Aug 2011
Posts: 8
Kent
Hi all, this is my first ( of many probably ! ) post on the forum.
Just bought a 59'Wideline with a 60'pre unit engine with Norton box and Commando primary case in lots of rusty and Knackered bits. The previous owners ideas of building consisting of hammers, selection of screwdrivers and Devcon !

Now for no.1 question. Would it be better to replace the crankshaft with a unit one if I wanted to fit belt drive,
ie is the unit crank longer on the drive side, and are there any issues, apart from machining to fit to the crank cases the Commando primary cases ?

Our friend used his selection of screwdrivers to pry out the crank seal with his usual skill so I am looking at Britechs Pre-unit Main Shaft Oil Seal Kit or the similar one from Classic Cycles, any thoughts ?


Sorry to sound lazy but it was totally stripped including bearings, bushes and flywheel and the inner primary ground out by hand way oversize to 'fit' , so any advise is totally appreciated !

Finally, honest ! what crankshaft balance factor would be recommended for 750 ( Morgo barrel on order ) in the wideline frame, Atlas, 650 or 750 Triumph or something different ?
Tune will be fast road ( standard Bonneville cams and compression, balanced and polished crank and 69'Bonneville cylinder head and carbs ).

Any help, advise, or words of encouragment much appreciated !

Cheers,

John.

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#394169 - 09/12/11 8:44 pm Re: Pre unit Triton, Unit crank ? [Re: john deering]  
Joined: Jan 2006
Posts: 6,643
GrandPaul Online content
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GrandPaul  Online Content
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Joined: Jan 2006
Posts: 6,643
Laredo (South) Texas, USA
Buffalo Bearings supplies the plug-and-play bearing to install unit cranks in pre-unit engines. Sorry, I don't have the part number, but ask if they show "Born Again Bikes" on thier client list, they should then have the reference.


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"
#394186 - 09/12/11 11:00 pm Re: Pre unit Triton, Unit crank ? [Re: john deering]  
Joined: Nov 2009
Posts: 571
bon Online content
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bon  Online Content
BritBike Forum member

Joined: Nov 2009
Posts: 571
Tony hayward should be able to sort you out a belt drive kit to fit your pre unit crank, he does them even for the pre unit rigids with the long chaincases.

#394244 - 09/13/11 6:12 am Re: Pre unit Triton, Unit crank ? [Re: john deering]  
Joined: Jul 2009
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
I thought a '60 engine would already have the one-piece crank as standard.
A later one,up to '71, should fit your bearings.'72 the timing side mainshaft increased to 30mm.
I think there's some issue with the thread on the timing side being longer on unit cranks.Check that it doesn't interfere with the bush in the timing case.There's nothing wrong with the bush seal;people are having more trouble lately with the rubber seal.

Most people use 85% balance-factor (dry) on a Triton.I doubt that you'd notice much difference between 70% and 85%.Norton engines are happy at around 74% (dry),and they lose more balance-factor when the crank is full of oil.The Norton riders are suggesting anything from 70% (like a 650SS) to 78%.77%-78% seems popular for Norton twins in featherbed frames.If anything,I'd expect a Norton to use a higher balance-factor than a Triumph,because of the rod/stroke ratio.

It would be worth crack-testing and tuftriding the crank;it will last 10 times longer before it breaks.

Locate the crank to the timing-side bearing,and use a roller on the drive side.This might help: Crank Location


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