I recently aquired the above brushcutter and although it was initially
running well, it will no longer start. A few times it has been
running ok and then stopped fairly abruptly, maybe after 30 mins use
or so !

Having removed the fuel filter (end of the fuel line in the tank) it
is now getting fuel (The plug is getting wet). It seemed to be quite
dry prviously, although it must have been getting some fuel or it
wouldnt have run at all. The filter seems to be some sort of porous
substance that allows fuel to "seep" through. The plug sparks fine
and even runs in my Mountfield lawnmower.

I've set the "L" screw to 1 1/4 turns out and the "H" to 1 turn as
prescribed by my local repairer, but still no joy ! Albeit maybe 3 in
300 pulls, it has tried to catch but not fully. After this the
cylinder is quite hot to the touch, so there is evidently something
going on.

The repair agent spoke of an impulse vent/port/something that may be
blocked between the carb and inlet. Anyone any idea ?

Beyond that I may have to resort to taking it to the Brushcutter Dr
but would prefer to make an attempt at fixing myself first !

Anyone feel they can help me ?

(Col Forsyth) wrote:

Hello Col

CF I recently aquired the above brushcutter and although it was
CF initially running well, it will no longer start. A few
CF times it has been running ok and then stopped fairly
CF abruptly, maybe after 30 mins use or so !

Aha! A *proper* strimmer! I got two. (One for work, one for home)

One of them recently exhibited similar problems. It's Ok to start, but
won't idle and cuts out when you lift the head. But I think both our
problems are related - fuel supply.

CF Having removed the fuel filter (end of the fuel line in the
CF tank) it is now getting fuel (The plug is getting wet). It
CF seemed to be quite dry prviously, although it must have been
CF getting some fuel or it wouldnt have run at all. The filter
CF seems to be some sort of porous substance that allows fuel
CF to "seep" through. The plug sparks fine and even runs in my
CF Mountfield lawnmower.

It's unlikely to be the plug, but it is still possible. Wet or dry is
not relevant - what is is the colour. White means it's not getting
enough fuel and running hot. Black means its getting too much fuel.

The end of the porcelain should be a "light biscuit brown". This could
be down to air or fuel blockage (likely) or tuning.

CF I've set the "L" screw to 1 1/4 turns out and the "H" to 1
CF turn as prescribed by my local repairer, but still no joy !

I was going to suggest that...

CF Albeit maybe 3 in 300 pulls, it has tried to catch but not
CF fully. After this the cylinder is quite hot to the touch,
CF so there is evidently something going on.

The cylinder can get warm just by the compression of the air, it
doesn't mean it's firing. You should be able to hear it fire, though.

CF The repair agent spoke of an impulse vent/port/something
CF that may be blocked between the carb and inlet. Anyone any
CF idea ?

Sounds very likely. What I did, and what has worked is:

Remove engine cover. Wash it in a bowl of soapy water.

Clean EVERY crevice of the engine housing. Compressed air is perfect,
but patience, a toothbrush and soapy water is almost as good. Get rid
of all muck, seeds, fluff. Clean out the block fins - everything.

Close choke, remove air filter. Wash in soapy water and dry. With
filter removed and strimmer turned so that the carb throat is not
facing upwards (to prevent any oddments falling in), open the choke
and inspect. Usually clear, but a cotton bud in petrol will remove any
muck. Also clean the inside cover of the filter. Replace filter.

Remove the four allen keys that hold the start cord assembly on.
Remove. Clean this thoroughly AND the fan inside the engine too. Can
get very dirty as this is the first place muck meets when it's sucked
over the engine. Wash the assembly in soapy water and dry. Also clean
the two dogs on the assembly carefully and give them a light grease.
When refitting - introduce gently and pull the cord slowly until you
hear the dogs "click" into position - too rough and they can snap off.

This thorough clean is a good yearly service thing to do just before
winter, and a liberal spray of WD40 over everthing just before you put
it away is a good idea too.

Now retry with the cover off (but air filter in place) - keeping your
hands away from the spark plug and HT circuit. It may run sluggish a
few seconds if the air filter is still damp, but will clear quickly.

You've removed the fuel filter (bad idea for a long period, btw). They
can be replaced cheaply and worth doing anyway. Another thing is to
remove the fuel line from the carb and blow down it to ensure it's not
blocked. Fuel lines can perish and collapse, or get pinched in the
case - the only way to check is to suck through it - but ensure fuel
tank's dry first...

If it runs for a bit then cuts out, try freeing the fuel cap. The
breather section in the middle can block sometimes causing a vacuum -
you'll hear a small hiss if this is the case.

If all *that* fails, the next step would be to take the carby apart
and clean it - but that can be very fiddly and might be worth leaving
to your expert. It's possibly the diaphragm has a puncture which will
make it run very lean.

HTH, any probs just ask.

--
Simon Avery, Dartmoor, UK Ý http://www.digdilem.org/

"Simon Avery" wrote in message
...
(Col Forsyth) wrote:

Aha! A *proper* strimmer! I got two. (One for work, one for home)

One of them recently exhibited similar problems. It's Ok to start, but
won't idle and cuts out when you lift the head. But I think both our
problems are related - fuel supply.

The end of the porcelain should be a "light biscuit brown". This could
be down to air or fuel blockage (likely) or tuning.

Yep, plug is/was a light biscuit brown. Bit damp now from excessive
attempts at starting.

Remove engine cover. Wash it in a bowl of soapy water.

Close choke, remove air filter. Wash in soapy water and dry.

This is about the only thing I havent done.

Remove the four allen keys that hold the start cord assembly on.
Remove. Clean this thoroughly AND the fan inside the engine too. Can
get very dirty as this is the first place muck meets when it's sucked
over the engine. Wash the assembly in soapy water and dry. Also clean
the two dogs on the assembly carefully and give them a light grease.
When refitting - introduce gently and pull the cord slowly until you
hear the dogs "click" into position - too rough and they can snap off.

Yep, had all this off and cleaned everything. Had the pickup off and
refitted
with the 10 thou clearance to the magnets as suggested by repai man.


Now retry with the cover off (but air filter in place) - keeping your
hands away from the spark plug and HT circuit. It may run sluggish a
few seconds if the air filter is still damp, but will clear quickly.

Nope, no such luck !


You've removed the fuel filter (bad idea for a long period, btw). They
can be replaced cheaply and worth doing anyway. Another thing is to
remove the fuel line from the carb and blow down it to ensure it's not
blocked. Fuel lines can perish and collapse, or get pinched in the
case - the only way to check is to suck through it - but ensure fuel
tank's dry first...


With the filter ON and the fuel cap FITTED I blew down the pipe and hey
presto
a fountain, so I guess the filter is ok !

If it runs for a bit then cuts out, try freeing the fuel cap. The
breather section in the middle can block sometimes causing a vacuum -
you'll hear a small hiss if this is the case.


Thought about that, but no such luck. Been slackening it every dozen or
so pulls.

If all *that* fails, the next step would be to take the carby apart
and clean it - but that can be very fiddly and might be worth leaving
to your expert. It's possibly the diaphragm has a puncture which will
make it run very lean.


Had the carb off, gave it a good blow thru. Nothing obvious. Diaphram in
good
condition as was the rubber tip on the main needle. Also discovered the
breather thru
into the inlet that he spoke of, seemed fine.


HTH, any probs just ask.

--
Simon Avery, Dartmoor, UK Ý http://www.digdilem.org/


Guess its gonna have to be a trip to Dr Huskie ! However, thanks very much
for
the extensive reply. I'll let you know what fixes it !!!

Col