Piston scoring symptoms?

[Pstuffel]

I remember being told that depending on what side of the piston gets scored it is indicative of bad air or bad gas. So any help? I am replacing two pistons and cylinders with the scoring on the muffler side right now.

 

[BostonBull]

Muffler side is usually a lean seizure, too little fuel, lots of air OR straight or under mixed gas/oil combo.

What color was the plug? Smoke grey, or cocoa brown?

 

[Pstuffel]

Plug was dark lots of carbon build up.

 

[BostonBull]

wasnt straight gas then

 

[Pstuffel]

I mix all the gas that goes through 24 260's. We dont have a huge problem with burning up saws but it does happen. The saw in question is only about 8 months old. I tend to take an "it happens" attitude because these saws see allot of different sawyers and allot of abuse. I would just like to start narrowing down the possible causes to avoid $200 repairs in the future.

 

[BostonBull]

very dirty ilter, or no filter

messing with carb adjustments

dull chain and pushing the saw too hard

air leak formed and was ignored

 

[Pstuffel]

Thanks for the insight Boston. My Idea is bad filters for sure. Carb adjustments are a no no for our Corps members. Dull chain is another possibility.

 

[flyingsquirrel25]

Dont forget to mention Ethenol. A change in ethenol rates in the gas you buy can cause a change in the way the saw runs. Thus creating the "out of adjustment" problem. Train your guys to listen for the screaming saw, and to stop running it when it happens. With proper adjustment for those changes a saw can last a long time.

When the saw starts running different check list:
Fuel? running out? When you hear it dont keep running it.
Air? Is the air filter cloged (Stihls are known for this)
Fuel filter? is it clogged
Adjustment? Why is it out? Air leak? change in fuel? repair problem

This is where I start. Anyone want to add anything else?

On the ethenol question... Has anyone used the pre mix stuff 50fuel?