What causes scaring on intake cylinder wall?

Hello everyone!

I would like to find out more info since, I'm not getting it from my mechanic. What causes scaring on the intake cylinder wall on Yamaha YZ426 motor?

My crank was off by .010 so my mechanic trued the crank back to .001 . Would this cause my motor to run very hot and cause my piston hit the cylinder wall on the intake side?

Has anyone else experience this same problem

Please let me know

:thumbsup:

YZ426 motor if this helps

Dirt getting past the air filter usually is the cause. When I've torn my bikes apart in the past, if the motor has many hours on it, you'll see this. When changing the air filter, it's crucial to be careful not to let any dirt drop in the air intake.

Dirt getting past the air filter usually is the cause. When I've torn my bikes apart in the past, if the motor has many hours on it, you'll see this. When changing the air filter, it's crucial to be careful not to let any dirt drop in the air intake.

I change my air filter after every ride and this motor has less than 5 hours since last rebuilt, which I was told. But I noticed this motor had the same wear marks as it did on the last cylinder, which came with this engine.

Thanks

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