Motorcycle Repair: Klr 250, check air filter, air leaks

Question
QUESTION: I have a 1999 klr 250 that I bought. The bike had been sitting outside for a while. I cleaned gas tank, carb and changed spark plug, and fluids. After a few kicks it started and ran great. Ran probably 2 or 3 times and no problems. Parked it and came back on a week. Started right up and responded fine until 3rd gear, then engine started losing power and then cut off. Cranked right up and same outcome. If I keep it revved, it will behave erratic. If I bring the RPMs it will stay for a short period, then start popping and then die. It is then hard to start, but will eventually. Any suggestions?

Thanks
Stan

ANSWER: Hello Stan,

First thing I would check on these
bikes is if the valve clearance
is okay. If none of the valves are too
tight then it might be a sticky valve.
Run some ATF in the fuel for a bit.

The exhaust camshaft has a decompression device on
it's end. See if the spring is missing.
It could be sticking and lowering your compression.
http://photos.smugmug.com/photos/99727251-M.jpg

Sometimes fuel tanks will have rust particles
after sitting so long.
Invest in an inline fuel filter if it doesn't
have one. Dirt or rust or moisture can
stop the engine quickly as the carb idle and
main jets are small.

Even after a carb clean the carb can plug
quickly if the fuel is not clean.
If the center main jet plugs it will affect
3/4 to full throttle running.

Check that the carb slide is not sticking
in the carb bore. It has to lift up and down freely.

If you didn't soak the carb it might be a good idea.
Use yamaha carb cleaner or boil the carb in lemon
juice for 20 minutes and blow out all the passageways.

The main and idle jets should be cleaned with
guitar wire or such to make sure they are clear.

Check that the carb is installed tightly with
no air leaks on the intake tube.
Air leaks can lean out the fuel mixture causing a misfire.

Check air filter is clean.

There is also a fuel filter on the fuel
petcock valve inside the tank, it might
be plugged up.

Tank air vent needs to be clear.

Check spark plug color for clues on
the problem:
http://verrill.com/moto/sellingguide/sparkplugs/plugcolorchart.htm

Use NGK plugs and make sure your spark
can jump a 5mm (1/4")gap.

Last resort might be cleaning all
the electronic ignition connections
with a good electronic spray cleaner.
A loose connection can wreak havoc.

Luck!
Wayne S.

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---------- FOLLOW-UP ----------

QUESTION: Thank you so much for your response. I never imagined I would get such a detailed response. One other question.

You stated "Run some ATF in the fuel for a bit."

You mean Automatic Tranmission Fluid in the tank or am I being stupid here and ATF stands for something else?


Also, how much do you mix in the tank?

Thanks Again!
Stan

Answer
Stan,

yes, ATF is auto trans fluid.
It is a good substitute for a
top end engine lubricant.

You can also use any top end fuel
additive you can find locally.

Just add an ounce or so as it may
cause some exhaust smoke.

Often sputtering is a lack of fuel
but a spark plug reading should tell
you that. Black is too much fuel and
light colors mean lean or hot fuel mixtures.

Wayne S
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