Motorcycle Repair: rf900r lacks power, plug colors, plug caps

Question
hi,

i just bought a 1994 suzuki rf900r that had been sitting for several years. i can
usually figure out these problems, but i am stuck. when i got it, it dint run
because the gas was bad, the carbs were gummed up and the tank was rusty, and the
ignitor was bad. so i cleaned the carbs and tank, put a liner in the tank, and
replaced the ignitor. i also changed oil/filter, and replaced spark plugs just
because.

the bike was running perfectly in rpms below around 7000, but it was stuttering and
topping out at like 120. about forty miles later, it has lost power and has a hard
time pulling away from a stop and tops out at 70. i pulled the muffler off: same
problem. gas from tank is flowing smothly and is clear. all carbs are clean and are
sending gas through. i suspected the valves, but i opened the top and i think they
are the shim type and the bike has only 10,000 miles on it. spark plugs are firing
when i pull them out and push starter button (while grounding). when i pull away
from a stop, and give it a lot of gas, it balks and as i continue to give it gas and
roll away the engine makes noise as if it is making power but it is not.

thanks for any help


Answer
Dana,

-are all the pipes warming up the same?
-Is it running on all the cylinders?
Check the plug caps, coils, connectors.
Do you have a fuel filter?

-It almost sounds to me like the clutch
is slipping badly. Do the rpm's speed up
but the bike doesn't?
-Check out the clutch plates, maybe they are
burnt out.
-If clutch is okay, check the compression and
or get a leakdown test. Should have
150 psi or higher.
-Also make sure air filter has lots of air
space available and is not plugged.
-Check your spark plug colors for clues,
black=too much fuel, whitish=too lean on fuel,
light brown= good combustion and fuel mixture.