QuestionHi there, I have an 83 GSX550e which struggles to idle and is very flat at low revs. I always need to use full choke to get it started and have to resort to bump starting regularly. The plugs seem fine and I'm guessing it a carb issue. Is stripping / cleaning the carbs the best first step?
AnswerHi Steve,
The idle fuel mixture is handled mostly by
the idle jet in the carbs. If the fuel
has evaporated and left some varnish in
the jets they may be causing your lean idle
condition.
You may want to check the whole fuel system
starting from the fuel tank.
Replace or clean any fuel filters you have.
Also check that the carb mounts are not leaking
vacuum or air into the intake.
Sometimes rubber can dry out and crack
allowing air to lean out the fuel mixtures
at high vacuum or idle speeds.
I would get some safe yamaha carb cleaner
and soak the whole carb(s) in it.
Remove any obvious rubber or plastic parts
but the yamaha brand cleaner will not
harm any parts like other carb cleaners.
After a few hours minimum soaking blow the carb
passageways out with air.
The idle and main jets should be checked
physically for varnish or dirt etc.
Use some smooth line like guitar string
or fishing line to probe the jets clean.
This might be a good time to check
the float valves and the float valve seat
o-rings.
Here is a general carb cleaning document
that will guide you through carb cleaning.
http://www.thegsresources.com/files/GS%20Carb%20Cleaning%20Series.pdf
Turn your idle mixture screws out a couple of
turns and adjust them from there to where the idle is best.
I think it should improve your starting
and idle response if you get some fuel
flowing again and check for air leaks.
To get a good response from the carbs you also
need reasonable compression readings.
You may need to check the valve clearance
and compression if the problem persists.
Good luck!
Wayne S.
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