Had this saw probably 10 years but only put 5 or 6 hours a year on it. The original symptom had it bogging down sometimes at full throttle then started to loss power more frequently. Usually this meant a good cleaning and it would be back to normal but not this time, eventually it would not stay running. It sat for a couple of years and I thought I would try it again, now it wouldn't start. Replaced the leaking fuel lines, fresh gas, disassembled and cleaned the carb, eventually bought a new carb, replaced the filter, swapped the plug and tried again. It will start now but will only idle for about 3 seconds and stop. Sometimes I could get the rpm up but it just bogged down. Pulled the choke abit and it died instantly, tried multiple jet settings but no help. One symptom I noticed that doesn't seem to happen as much on my other 2 cycles is something I noticed in the priming circuit. Should I pump the bulb fast/hard I get alot of air thro the circuit, not so if it pump it slow. I don't see bubbles in the line coming out of the gas tank pumping the bulb hard. Can it suck air somewhere through the carb circuit even if all is normal or is this a symptom of a bad pump diaphragm?
Husqvarna 240 won't run
- Thread starter teseal3
- Start date
The purge valve is not so much priming to a pressure- as it is purging the carb of air by replacing it with fuel.
Incorrect assembly or connection of lines to and from the purge valve will suck air back in- rather than fuel.
Lack of compression, massive air leaks will stop a saw firing up if all else is present.
Remove the muffler and lets see the piston as viewed through the exhaust port.
Or- keyway sheared on the flywheel- timing a long way out and spark at wrong point in compression stroke- saw wont go.
Fact it will run for a few seconds and die if you get on the gas- Im picking low compression and torn up piston.
Incorrect assembly or connection of lines to and from the purge valve will suck air back in- rather than fuel.
Lack of compression, massive air leaks will stop a saw firing up if all else is present.
Remove the muffler and lets see the piston as viewed through the exhaust port.
Or- keyway sheared on the flywheel- timing a long way out and spark at wrong point in compression stroke- saw wont go.
Fact it will run for a few seconds and die if you get on the gas- Im picking low compression and torn up piston.
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Thx for your reply Bob. I did check the bulb lines to make sure it draws thro the filter out of the tank and returns to the short line.
I had the carb, both carbs, apart several times without a change much in the symptoms so I'm thinking odds are less for mis assembly.
I can check the compression, any idea where it should be? There is what seems to be normal resistance when I pull the starter rope.
I will inspect the piston and shaft key and get back to you. Appreciate you.
I had the carb, both carbs, apart several times without a change much in the symptoms so I'm thinking odds are less for mis assembly.
I can check the compression, any idea where it should be? There is what seems to be normal resistance when I pull the starter rope.
I will inspect the piston and shaft key and get back to you. Appreciate you.
Compression needs to be around 120 psi- have seen saws run at 90- but not very often.
However, you cannot use a standard automotive tester and expect a true result- often the valves in the lines are too stiff to allow a true reading- ideally you need a tester designed for small single cylinder engines.
However, you cannot use a standard automotive tester and expect a true result- often the valves in the lines are too stiff to allow a true reading- ideally you need a tester designed for small single cylinder engines.
Depending on the tester used- 110 might be more like 150- or it might be 110.
Easiest Bubba sneak around is to remove the spark plug, tip say a teaspoon of oil on top of the piston- swill it around a bit and try to start the saw with the plug back in.
The oil gives a temporary and false compression boost- if it starts it will kill any mosquito within 100 yards- but will also prove compression is down.
Pressure and vacuum test would be a good idea- airleaks if good enough will stop a saw from running.
Easiest Bubba sneak around is to remove the spark plug, tip say a teaspoon of oil on top of the piston- swill it around a bit and try to start the saw with the plug back in.
The oil gives a temporary and false compression boost- if it starts it will kill any mosquito within 100 yards- but will also prove compression is down.
Pressure and vacuum test would be a good idea- airleaks if good enough will stop a saw from running.
Prior to the pressure test and piston check I did, I had also switched the carburetors, I have two of them one is new only didn't know which one it was. After switching carbs I could not get the saw to even pop once.
When I was removing the muffler to inspect the piston I noticed how dirty the spark arrestor was. Checking it again before reassembly decided to take wire brush to the screen which was nearly solid with carbon. Thought I would give it a try before checking the shaft key and the darn thing popped on the first pull. Few pulls later it fired up, going to need the carb adjusted just didn't have time or tool yesterday.
It's my spare saw so I'll get to it when I can, got to find that damn carb tool, but I think it is as they say "out of the woods." I'm guessing the screen was keeping it from breathing decently. You agree or is that too easy?
Thx for your expertise, appreciate ya, be safe.
When I was removing the muffler to inspect the piston I noticed how dirty the spark arrestor was. Checking it again before reassembly decided to take wire brush to the screen which was nearly solid with carbon. Thought I would give it a try before checking the shaft key and the darn thing popped on the first pull. Few pulls later it fired up, going to need the carb adjusted just didn't have time or tool yesterday.
It's my spare saw so I'll get to it when I can, got to find that damn carb tool, but I think it is as they say "out of the woods." I'm guessing the screen was keeping it from breathing decently. You agree or is that too easy?
Thx for your expertise, appreciate ya, be safe.
Yes= I totally agree- and something I often forget in the list of obvious go to's .
A carbon plugged spark arrestor screen or muffler full of insect nest will stop a saw starting.
Often caused by a heavy oil fuel mix and or rich tuning. The top of the piston and exhaust port can become clogged up with carbon as well under the same conditions.
I am used to bugger saws and the fact most bigger saw users un the Americas delete the spark arrestor screens soon as they get a saw and more often than not modify the mufflers with more outlets before the get go,
Apologies for not suggesting check the screen earlier- but well done you for finding it.
EDIT: easier than wire brushing the removed screen and more thorough- is to hold the screen with pliers and burn it clean with a propane/map gas torch.
A carbon plugged spark arrestor screen or muffler full of insect nest will stop a saw starting.
Often caused by a heavy oil fuel mix and or rich tuning. The top of the piston and exhaust port can become clogged up with carbon as well under the same conditions.
I am used to bugger saws and the fact most bigger saw users un the Americas delete the spark arrestor screens soon as they get a saw and more often than not modify the mufflers with more outlets before the get go,
Apologies for not suggesting check the screen earlier- but well done you for finding it.
EDIT: easier than wire brushing the removed screen and more thorough- is to hold the screen with pliers and burn it clean with a propane/map gas torch.
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