FH primary alignment?

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Simonjones
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FH primary alignment?

Postby Simonjones » Wed Dec 26, 2018 8:05 pm

Hi guys.

I’ve fitted a BSA A10 into a 58 Ariel frame.
I assumed that this would be an easy enough job as I thought the engine was basically the same in many ways to the FH.
Well I’ve already found that it isn’t quite the same as FH engine plates weren’t quite right to pick up the mounting holes in the crank cases.
I had some plates laser cut and the engine is now in.
My next hurdle is aligning the engine sprocket with the clutch sprocket.
The clutch sprocket with its thrust washer (3394-36) fitted needs spacing out about 4mm from its existing position.
The gearbox is a Burman GB39 that was running a two plate clutch. I was expecting to change the clutch centre and outer basket to run three plates.
Question is, Is the main shaft longer on an FH gearbox. I could easily get a thicker thrust washer made but is that the answer??
Is the engine sprocket the same for the A10 and FH??
I’d really appreciate some advice from any FH experts.
Many thanks Simon
1950’s NH350 bitsa 1949 Triumph Speedtwin

Mick D
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Re: FH primary alignment?

Postby Mick D » Thu Dec 27, 2018 8:38 am

Hi
I'm certainly no FH expert but have just started a restoration of one.
GB44 main shaft lengths are detailed in section 19 of the Draganfly catalogue - I also received clarification from the 'Forum', see my post earlier in this section titled GB44 Main Shaft
Regards Mick

Simon.Gardiner
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Re: FH primary alignment?

Postby Simon.Gardiner » Thu Dec 27, 2018 12:48 pm

Simonjones wrote:Hi guys.

I’ve fitted a BSA A10 into a 58 Ariel frame.....

A very very difficult feat. Well done to have got so far (although the Ariel and BSA internals are identical almost every external part is so different as to be completely non-interchangeable!)
I'd suggest you have a good look at the engine sprocket spacing before deciding to move the clutch sprocket. The engine sprocket/shock absorber is pretty much the same for A10/FH but there are a variety of spacers used between the shock absorber assembly and the drive-side main bearing and in my experience that's where you need to look first if there are issues with the chain line.

HTH

SG
'55 Huntmaster, '56 VH, ' 51 VH, '80 R100RT, '00 Sprint ST (but all those Ariel parts can only make one running bike...)

Simonjones
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Joined: Wed Nov 09, 2016 8:05 pm
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Re: FH primary alignment?

Postby Simonjones » Fri Dec 28, 2018 8:27 pm

:) Thanks for the replies chaps.
Yes Simon, I will look into what can be done with the engine sprocket although I don’t recall there being a space behind it on the BSA. I think the engine sprocket has a shoulder on the back of it that gives it the spacing. Of cause I could get that machined down slightly too.
I’ll work something out eventually! :)
1950’s NH350 bitsa 1949 Triumph Speedtwin


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