If it's running stably in that position you're not hurting anything. For
some reason the mixture with the choke off is too lean and leaving it
partly on corrects that. The engine is then getting what it needs.
It *should* be repaired but it's not like it's hurting itself if it's
Of the possible causes previously given it won't be a dirty air cleaner as
that would have the same effect as the choke, richening the mixture. Fuel
filter....maybe but I wouldn't bet money on it. Carb adjustment...well
that doesn't change by itself but readjusting it could fix things. (Back
off the main carb adjustment screw maybe a turn and see if it then runs
I would guess the problem is caused by dirt in the carb's fuel passages.
Repair would require disassembly with some tiny parts to deal with and you
still might never find anything specific but a general cleaning and
reassembly might correct that. But that might not be something you want to
get into. For now I would just try readjusting.
If it's a halfway recent engine, it won't even have any mixture
adjustments. Some of these consumer grade engines won't run right,
brand new. However, the OP said it used to run OK, which means the carb
probably needs a thorough cleanout.
I had a gas powered weed eater with the same problem. After many
(self done) failed fixes the final problem was found to be a factory
assembly problem where the cylinder head was not tightly secured to
the crankcase. This allowed air to get in during the crankcase
suction cycle and therefore degraded the carb suction. A half choke
permitted enough suction for the engine to operate. Of course it
became worse with time. Just something simple you can check on. Make
sure all the screws are tight. Do not over torque.
Of course, if you can, clean the carb, the fuel line and the fuel
filter. In an earlier case of a cranky lawn mower the problem was
traced to "dissolved" grass scraps forming a slimy cellulose fiber
film over the fuel filter screen. The cellulose film was barely
noticeable on casual inspection. The grass scraps got into the fuel
tank when refeulling and my not taking care to clean the funnel
throughly before pouring.
Probably the gasket between the carb and the side of the engine is missing
or damaged. It could be sucking in unfiltered air, which might contain dust
and dirt. That could damage the cylinder.
I'd try to get it fixed.
Christopher A. Young
"BoyntonStu" < email@example.com> wrote in message
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