Thanks again for the helpful reply.

"Alan" wrote in message
The carburettor has 2 tuning screws.

There is only one on my machine (which I think is a 2001 model) and it's
marked 'H......L' on a circle.

My much older Stihl 015AV chainsaw has 2 screws as you remark.

These should be tightened (not too tight!) and then slackened 1 turn
(ie 360 degrees) to give the correct tuning.
If this doesn't work, judging by your symptoms, you can try opening the
low speed screw (the one nearest the engine block) a little (1/4 a turn
or so)

I don't think it is the gauze in the exhaust (spark arrester) as that
would prevent it revving as the previous poser says. A clogged fuel
filter would have the same symptoms.
Are you sure the fuel is OK? - stale fuel is a common problem with
similar symptoms. Have you tried emptying the fuel tank and using
freshly bought fuel - run it for a minute or so to clear out any old
fuel?

Thanks, I'll try that although I thought that I was using recently purchased
fuel.

I'm not convinced about the plug being the problem either. I think that
if the tuning or fuel doesn't sort it then I would have it
professionally looked at in your local repair place. My money is on a
carburettor problem. Please let me know what the problem is. I am
intrigued.

I have noticed that the black ?plastic? flange where the carb. fixes onto
the cylinder body has a hairline crack in it - I'm wondering if too much air
is getting in, but to me that would seem to show up at bad starting -- it
starts easily enough.

regards,
Mutley