Qualcast 2 stroke strimmer sometimes won't stop after use. I've changed the switch and will see if this cures the problem. I'm wondering if a 2 stroke can run if the plug isn't sparking, like a car engine "running on" ? Maybe the shorting coil is breaking down when hot?
Strimmer won't stop...
- Thread starter DaveHerns
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The switch effectively connects the ignition module to earth and I'm sure this will sort your problem.
I've never heard of two stroke plugs getting so hot as to cause pre ignition - but it was an issue years ago with some carburettored cars. These were given a fuel shut off valve to cure it but the problem stemmed from incorrect ignition timing.
John
I've never heard of two stroke plugs getting so hot as to cause pre ignition - but it was an issue years ago with some carburettored cars. These were given a fuel shut off valve to cure it but the problem stemmed from incorrect ignition timing.
John
I shouldn't complain, most people post because they cant start or keep them running, you may have to judge it so you finish the job as it runs out of fuel
litl
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You stole my line! (No pun intended)I shouldn't complain, most people post because they cant start or keep them running, you may have to judge it so you finish the job as it runs out of fuel
litl
How does it stop? The shorting may be being stopped by a film of oil or something
I grew up with a lawnmower that was a pig to stop and the most important thing was to clean the bit that touched the plug to earth before starting
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A build up of carbon inside the cylinder can glow red hot and then act like a spark plug and ignite the compressed air and petrol vapour.
it's possible if it is badly coked up and there are glowing carbon deposits in the cylinder. it would run pretty rough.
edit
too slow
Have you checked for continuity between the earth side of the switch and the engine?
litl
litl
Love itI shouldn't complain, most people post because they cant start or keep them running, you may have to judge it so you finish the job as it runs out of fuel
litl
The scavenging (Schneurle effect - excuse the spelling) causes the carbon build up to be in the exhaust port and silencer of two strokes and won't cause 'run on'.
John
It does seem to happen mostly after a good session when it's hot . I'll see if the new switch does any good. This machine is a good starter and I can always stop it by closing the choke flap. Shouldn't really complain ,it's 6 years old.
Try whipping the plug cap off if it won't play ball.....but wear a rubber glove
John
John
Ive not seen a 2T run on in nearly 60 years of use and repair f them.
If you want to try flipping the plug cap, ease it off the springy part with an insulated screwdriver so you dont get a belt.
Back in the days when no suppressor caps were fitted I worked with an old guy who used to stop them by catching hold of the brass end of the the lead and pretty quick learned to keep beyond arms length from him, some will know just what Im talking about
litl
I guess the answer is yes - so long as there are glowing deposits within the combustion chamber. If the spark plug is the incorrect grade or the timing is way out then theoretically its glowing tip could do the same.
In practice, its an extremely rare occurrence, particularly in two strokes......I've never come across it, and that includes exhaust development work in my early days (1970's) with Rotax and JLO engines where huge revs were common place. Weak mixture never caused running on, but was sufficient to melt pistons - the heat was so great.
John
In practice, its an extremely rare occurrence, particularly in two strokes......I've never come across it, and that includes exhaust development work in my early days (1970's) with Rotax and JLO engines where huge revs were common place. Weak mixture never caused running on, but was sufficient to melt pistons - the heat was so great.
John
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