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wrote:
Nick no_bother@all wrote:

I have a Mountfield lawnmower with a Honda GCV135 engine. I tried to use it
the other day and although it started immediately it wouldn't run at a
constant speed. It slowed to a stutter and then speeded up then slowed down
and so on.
There is a linkage between the carburettor and a spindle projecting out of
the engine casing. This is oscillating backwards and forwards. I know what
it's connected to at the carburettor end but have no idea what the spindle
is connected to inside the engine.

That's the speed regulator, there's a flap inside the cowling which
gets pushed by the flow of air as the engine speeds up, this closes
the throttle and (if it's all working correctly) should prevent the
engine from over-revving.

Please can anyone suggest what might be going on?
I've done the obvious things like renewing the spark plug, cleaning the air
filter, checking for fuel line blockages. Next on the list is to strip down
the carb. but I thought I'd post here first.

It sounds like fuel starvation, so double check the fuel lines first,
then I think your next move is probably what you said, there may be a
blocked jet in the carburretor.

It may also be worth cleaning out all the accumulated grass and gunk
that's in with the regulator flap too.

I agree entirely with usenet's statement.

Also, the fuel pick up in the petrol tank has a mesh filter which tends
to block.