"robinfrance" wrote
My first post on this forum, so a brief intro: we're Brits living in
northern France (Normandy) for the last four years, though hoping to
return to the UK in the new few months.

I have a mower with a Briggs and Stratton XP40 mower which is not
running well. This will be only its third year of use, and I've never
had a problem with it until now. I used it for the first time this year
a few weeks ago – no problem, seemed to be running as normal. I then got
it out again last week and found that it wasn't running smoothly. I
would say the engine seems to be "hunting" – almost like it's coughing
slightly – it sounds at various points as though it's going to die but
always manages to keep going. Two further symptoms: (1) puffs of black
smoke are visible by the grill on the L/H side, and (2) it used an
awful lot more petrol than usual when I cut the grass with it the other
day.

I'm no mechanic, but have done my best to do the basics in an attempt
to rule out obvious causes: I've cleaned the air filter (seems fine),
taken off the plastic engine cover and cleaned round everything I can,
and changed the oil. Doesn't seem to have made any difference.

One other thing I've noticed: when first starting the engine (even
after only a few minutes' break in running), it seems to run nice and
smoothly for maybe ten seconds or so before starting to cough and
splutter again.

I would have taken it in for repair, but there's only one place in the
vicinity and they have a 3 week wait! I'd be very grateful if anyone
has any ideas or suggestions. (N.B. I've looked on the B&S site, but so
far only found quite generic advice that hasn't helped me.)

Thanks in advance,

Hunting is when an engine speeds up and then slows down of it's own accord
instead of ticking over. This is usually caused by fuel starvation and
usually a dirty carburettor is the cause, sometimes a knackered fuel pump
but mowers don't have those.

However you mention it's using a lot more fuel than normal and making black
smoke which suggests it's actually running rich. Others have mentioned a
stuck choke but it could also be a stuck float in the carburettor. My
suggestion is to remove, partly dismantle, and clean the carb, just taking
the top of is usually enough to clean it out (use petrol not water). Make
sure the float moves easily and that there is no muck in the float chamber.

--
Regards
Bob Hobden
just W. of London