Carburettor needles not staying where they should

[nobrob]

Hi all

I posted this on an alternative forum and didn't get much of a response, so I'm trying my luck here. My apologies if it's not the done thing.

I have two engines (two carburettors) and the needles (high speed and low speed) are both very easy to move. So much so that the high speed moves itself while the engine is running due to the vibration, annoyingly it moves itself inwards (leaner) until it's as lean as possible!

The only thing I think might be the reason is that I used to put after run oil in the carburettor, before being told it could cause damage, at which point I stopped.

Any thoughts on (a) why this might have happened and (b) how to fix it without replacing the seals?

Thanks