On 12/01/2019 14:04, rick wrote: I have a McCulloch 360T
Starts fine .. either hot or cold ... which in itself is a good
indicator that many things are Ok with the saw.

In use ... be cutting fine then revs will die, then get to a point with
chain out of the wood .... tickover is fine, but when I try to rev it
picks up, but after about 20-30% of power then dies off ... often to a
stall.
It can often take 10 or more attempts before it will get to point that
revs will open up .. then it cuts fine ... but a few minutes later it
will start again.

When it is revving it cuts fine with no loss of power.
If you quickly loosen the fuel cap after it has died does it suck air?
Similarly will it run for longer if the tank is half full rather than
full?
I have cleaned air filter, checked plug gap, used new fuel, general
clean to get rid of any oil or wood chip build up.

Always a good idea to have a new plug available, I have one here that
runs for 20 seconds then stops, it had me fooled for a long time as I
thought the fault was in the coil.

Apart from vacuum forming in the tank there are a couple of things:

1 cracked or leaky impulse line, this is the bit that communicates from
the crank case to the diaphragm pump in the carb, some say these
deteriorate due to increased ethanol in fuel.

2 blocked filter in gallery between pump and needle valve in carb, this
is a metal mesh. Occasionally this can also trap a blob of water which
leads to erratic behaviour.

AJH