Will 10w40 down a fuel injector resevoir on a 83 yamaha pw 50 hurt it?

The bike did not run long with the 10w40 in it before i changed it to 2 stroke but it hasn't run right since. I would like to get this bike running for my son but don't know why it runs so poorly. It will start after a lot of kicking but will only run on full throttle and will not idle. If this is a carbueration issue what do I do. thanks for any inputWill 10w40 down a fuel injector resevoir on a 83 yamaha pw 50 hurt it?It wouldn't hurt the engine.

Just foul the spark plug and leave a lot of carbon deposits in the combustion chamber (top of cylinder).

Drain the injector tank.

Fill with Yama-lube for injector type engines.

Remove the spark plug from the engine and %26quot;do not%26quot; connect it.

Try to start the bike for a minute or two (to get the 4 stroke oil out of the lines).

Install the spark plug and start.

If it still won't idle, you might have to clean any oil that got into the carb..

Turn the petcock to off.

Loosen the float bowl drain screw and drain the float bowl.

Loosen the clamps holding the carb to the engine and air box.

Spin the carb sideways and remove the float bowl.

Remove the pilot jet (long and thin).

Hold it up to the light. You should be able to see through it. Clean it until you can.

Put everything back together.

When you get it running, ride it at high speeds until it stops smoking (that will burn out the carbon and oil).
Will 10w40 down a fuel injector resevoir on a 83 yamaha pw 50 hurt it?
Sorry, I wasn't paying attention to the year of the bike. It's over 20 years old. If the piston %26amp; rings have never been changed, it's way past due.

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Will 10w40 down a fuel injector resevoir on a 83 yamaha pw 50 hurt it?
It will kill it, sounds like a piston ring or carbon problem take a compression test
I hate to say, but the piston and rings probably need replaced. The symptom sounds like very low compression. The engine oil probably did not cause the poor running, but 24 years is a lot of time on a piston that small. Your local Yamaha shop could check it out.