QuestionQUESTION: Hi, i just baught a 73' kawasaki 100 enduro. Lookd great for the age, runs great. Fires right up. Its 2 stroke. So, after i ride it for about 20-30 min it backfires a couple times n dies. I let it set for 10 minutes and it fires back up and runs great again for about 5 r 10 minutes. Then backfires a couple times and dies again. Even after a brand new plug. Ive worked on a lot of older 2 stroke yard tools like leaf blowers and lawn mowers and snow blowers and i know that there has been points r somehing that burns up in those engines and cause em not to run. But i know nothing about bike engines. Can u help me please?
ANSWER: Hi Brian,
It sounds more like a fuel problem to me at this point
since it dies after a fair amount of time passes.
A few things to check first are:
When it quits running check if there is pressure
or vacuum when you open the fuel tank cap.
Could be a plugged air vent in the cap preventing
fuel from leaving the fuel tank.
Next, make sure the fuel if flowing freely
from the tank shut off valve
to the carburetor.
I would highly recommend you put an inline fuel filter
in the fuel line on an older bike as there is always
bits of dirt or rust that can plug up the carb.
If that checks out it might need a carb clean and check
if the float inside the carb is free or sticking.
The carb on older Kawasaki's is inside the right engine
case as this is a rotary valve two stroke.
There is a disc that rotates on the crankshaft and
allows the fuel in at the correct timing moment.
The carb is removed by pulling out a small rubber
plug at the front of the engine case
and inserting a screwdriver to loosen the carb clamp.
The carb can be wiggled out after removing the outer
cover and loosening the carb clamp screw.
The ignition is under the left side engine cover.
There may be contact points under the flywheel
magneto there.
You have to purchase a puller to remove these flywheels
without damage but you may be able
to look through the inspection holes and
see if the contact points are opening
about .013" when the timing marks align on the
flywheel and the engine case.
The points should just break open when the marks
align. You can sometimes connect a light
or multimeter to the points wire to check
when they open or do a careful visual setting.
A timing light may work also.
If the points are worn they may not open properly
which may eventually cause running problems.
Check the fuel supply and carb first and then
the points, that should get you going.
Let me know if you need more info, nice bike!
Wayne S
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---------- FOLLOW-UP ----------
QUESTION: First off, thank you for all that info...i had no idea. Also i checked all the fuel issues and also replaced the fuel line. Still does it. I notice, it starts doing that a few minutes earlier with the lights on. Ive been doing a few things to get a better idea and i know that if the lights are on nd it starts to die i can shut off the lighrs and get an extra couple minutes of excellent run time. But after a couple more minutes it will die anyway. Almost like its losing electeicity until it doesnt have enough to run. Sounds weird i know, but i dont understand. Thats all i can figure out. Does that give u any other ideas? And also thank you for complimenting my bike...it is a pretty nice bike for its agen..if i could only figure out its immediate dieing issue of electrical power after 30 minutes. Its really got me stuck.
AnswerHi Brian,
By your description of the power loss I think you might
have a bad ignition component.
This could be just the ignition coil to the spark plug
is failing when it gets hot. By turning the lights off
you may be providing it with a bit more voltage
which keeps it going awhile longer.
There are a few older bikes which run off the battery
and need a good battery to run at all.
The other possibility is the coils under
the flywheel are failing to provide power
to the main ignition coil when hot.
The ignition switch is often wired to provide more
power to the battery when the lights are on.
My first attempt to solve this would probably
be to try another motorcycle ignition coil of similar
specs. Even some ordinary older car coils
might work just for testing.
The primary or smaller wire to ground
should read about 1 to 2 ohms.
If the coil still dies after a time
then I would buy a flywheel puller
so the lower coils and ignition points/condensor
could be checked.
Sometimes the flywheel magnets need to be sanded clean
as they can rust up.
If it happens to be a battery ignition bike
then you would need a fully charged battery
in good shape and then check if the
charging system is working.
It should charge about 13 volts on a 12 volt system
and maybe 7.2 on a 6 volt system.
Another way you may be able to test the coil
is buy some compressed air in a can
or maybe even an ice pack.
When it stops running spray the coil
cold and see if the bike will start up again.
If it starts when made cold then you know the coil is faulty
and just quitting when hot.
There are some cheap coils on ebay that might work
or get a new or used one from cycle shops or cycle
wreckers.
Wayne S
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