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I've never had this before. Genuine Italian GP200 manifold and genuine SH2/22 carb. Carb came loose and will not tighten up. Nylon carb sleeve looks fine but manifold stub looks like it's been fretting away reducing the diameter. I'm going to try a new manifold tomorrow. Let's see.
Paul.

if anything the plastic would wear first

hullygully wrote:if anything the plastic would wear first

I agree but parts came from different sources. I could well have thought it was tight when it wasn't.

Had this before, the nylon reduces in size due to over tightening, unlike rubber does not expand.

St George wrote:Had this before, the nylon reduces in size due to over tightening, unlike rubber does not expand.

I forgot to mention, it's even looser when mated to a brand new Jetex. I'm convinced the alloy has worn away.

I suspect that Jetex manifolds are slightly different in size to our Italian versions otherwise people would not be after Italian GP 200 manifolds.

The nylons do wear but so do the manifolds. If fitting a new nylon doesn't cure it you will need a new manifold. This was a common problem back in the 60s/70's

New manifold from Allstyles. Now a tight fit. The old, original, manifold was definitely worn.

Learn every day. Glad it's sorted.

St George wrote:Learn every day. Glad it's sorted.

Thanks. Yep, I've never seen the like before either.
Paul.

coaster wrote:The nylons do wear but so do the manifolds. If fitting a new nylon doesn't cure it you will need a new manifold. This was a common problem back in the 60s/70's

Resurrecting this as I've had a problem recently with the carb appearing tight but over a few miles it seems to rotate clockwise on the manifold resulting in the throttle cable becoming tight and lifting the slide.

Any tips on changing the plastic bushes?

Ross,

The conclusion of the above thread was that the most likely cause of the loose carb was the worn manifold.

Although people don't believe this, it is the ali manifold that wears out before the nylon insert. I have witnessed this many times.

Investigate the cost of a new manifold. You might be pleasantly surprised.

martin

Thanks, I may just replace both as a matter of course.

Just to answer my original question, if you remove the slide there are two points where you can get a small thin punch against the bush and gently knock it out, but it's unlikely to come out without some damage to the plastic. Once it was out I opened up the slots on the carb which were almost completely closed up.

Fitting the new bush is another game altogether...

In the end I got it in by squeezing it in the jaws of the workmate, it went quite a frightening shape before it popped in.

It seems to be very solid on the new manifold whereas the old one was distinctly wobbly until tightened. I just hope I don't have to take it off again too soon...