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My son's fairly new Stihl MS270 chainsaw engine has seized. It got hot and began running/cutting poorly so he shut it off. A while later he tried to crank it, and it won't turn. He is using Stihl oil in the gas; however, after looking back into the owner manual I see it specifies 89 octane gas, "using lower octane may cause the engine to seize."...he was using 87 octane.
Question: is there something we can pour into the cylinder and free it loose in hopes the engine is not too badly damaged to use?
Thanks

You can try filling the cylinder with deisel fuel and let it sit

Marvel Mystery oil sometimes works. But, it will only work if the piston is siezed to the cylinder. If the rod is siezed to the crankshaft, then a new rod & crankshaft will be needed.

Thanks for the replies. I put some diesel in it this morning.

The diesel worked. After sitting about 3-4 hours I did some gentle tapping on the pulley wheel and got it to turn.
With diesel fuel in the cylinder/engine, is there anything special I should do before trying to fire it up?
Thanks.

Now you take it apart , clean it out and see how badly damaged it was.

You might get real lucky and only need new rings,

essasmallengines said:

Now you take it apart , clean it out and see how badly damaged it was.

Click to expand...

That' s beyond my expertise, so will take it to the shop. My son and I have learned from this experience, and thanks for the help.

redka said:

My son's fairly new Stihl MS270 chainsaw engine has seized. It got hot and began running/cutting poorly so he shut it off. A while later he tried to crank it, and it won't turn. He is using Stihl oil in the gas; however, after looking back into the owner manual I see it specifies 89 octane gas, "using lower octane may cause the engine to seize."...he was using 87 octane.
Question: is there something we can pour into the cylinder and free it loose in hopes the engine is not too badly damaged to use?
Thanks

Click to expand...

fill it with marvel mysterty oil and let it sit for awhile then turn it over it should brake free easy you might have to hone it out depends on how bad its hurt new rings piston and barons it will run like new

It sounds to me like you may be running your engine a bit too lean. You can richen up the mixture with the two screws on the side of the saw, L for low and idle H for high speed. Probably wouldn't hurt to turn both out at least 1//4 turn counterclockwise, maybe more if the saw still runs all right.

a.palmer jr. said:

It sounds to me like you may be running your engine a bit too lean. You can richen up the mixture with the two screws on the side of the saw, L for low and idle H for high speed. Probably wouldn't hurt to turn both out at least 1//4 turn counterclockwise, maybe more if the saw still runs all right.

Click to expand...

Thanks, will try it.

Sorry to hear about your son's saw. If you get it repaired or you purchase A new saw do not use ethanol based fuel.
The alcohol in the gas cuts the oil film on the cylinder wall and there goes your lubrication. Seize up will shortly follow.
In my state (Minnesota) the hot rod and motorcycle lobby persuaded the powers that be to allow the sale of non-ethanol fuel for there older engines and it can also be used in small engines that can't tolerate the alcohol. Perhaps your state has the same program.

Good Luck!
harleyron74.

Harleyton 74

Hi i live in Mn in the southwestern corner and some of the smaller towns don't have gas without alcohol there gas i know this is because i don't use gas with alcohol in the gas in my cars because it get better mileage without it.And i don't use it in my small engines too.I have to go to Iowa to get reg gas with out alcohol in it.:tongue: