Carb problem.

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MalcW
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Carb problem.

Post by MalcW »

Hi all. I have recently bought an AJS Model 31 fitted with an Amal Concentric MK1 carburettor. I have found that if I nip up the nuts holding the carb to the inlet manifold, all is well. But if I fully tighten them the carb slide sticks. Anyone else come across this, or have any ideas? Thanks.
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thornebt
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Re: Carb problem.

Post by thornebt »

I think if you overtighten the nuts to the inlet manifold it distorts the body and can mis-shape the carb. That's certainly the case with the Monobloc carbs anyway. It's important to do them up just enough and use loctite, or maybe nyloc nuts. Bruce.
SPRIDDLER
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Re: Carb problem.

Post by SPRIDDLER »

Short answer: You're distorting the body by over-tightening the nuts.

It depends what you mean by 'fully tightening' ?
They only need be tight enough to compress the 'O' ring and prevent the carb from coming loose whilst riding.
Over-tightening will squash any spacer at the stud holes and distort the carb flange/body.
'There is a tide in the affairs of men
Which taken at the flood............'
alanengineer
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Re: Carb problem.

Post by alanengineer »

I agree with both above. Its only a zinc casting and distorts easily. Use nylock nuts and tighten just enough to pinch the 'o' ring
Mick D
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Re: Carb problem.

Post by Mick D »

Hi

In addition to the spot on advice given above, you may have inherited a carb where the flange has been distorted due to over tightening and nipping up may not allow the O ring to seal the joint.

I suggest you confirm that both the carb flange and the spacer are perfectly flat, check against a straight edge, (a good rule will suffice). If the flange is bowed it can be restored flat by taping a sheet of fine wet and dry paper, (around 400 grade), to a flat surface, (sheet of glass / MDF / surface plate), and linishing the flange face back to flat. If the carb was bowed I'd recommend replacing the spacer as a matter of course, (it's a lot more difficult to flatten a convex surface by hand).

Regards Mick
MalcW
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Re: Carb problem.

Post by MalcW »

Thanks all. Mick, checked the flange with a straight edge and it's OK, so as the others pointed out I think I was just being a bit over enthusiastic about tightening it down.
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