tree removal - chaisaw problem, wrog fuel mix

[tractchores]

I'm doig some tree work and i accidentally put the wrong fuel mix in my chainsaw. I have two saws, one akes 25:1 and the other 50:1. I put 25:1 in the 50:1 saw and ran half a tank. That saw (husqvarna 257) was running great before. With the wrong mix it was stalling out anytime it was reved or losing power. I discovered the issue and switched fuel, cleaned the sparkplug and it still has the issue. Starts fine, idles ok, but when revved loses power and stalls. I ran a half tank of the right mix and still have the issue. Before i bring it to the shop can anyone think of other things to check?

Done so far:
New sparkplug
Checked and cleaned exhaust and spark arrestor
Air filter checked and is clean
Air injection systqem checked and cleaned
New tank of properly mixed fuel
Chain spins freely

 

[murphy1244]

Run a shot of Sea foam in it.

 

[Gary Fowler]

With the low oil ratio, you may have burned the rings out and may require an overhaul. Hopefully there was enough lube to keep the piston rod lubricated.

 

[BukitCase]

Uhh, Gary - he used 25:1 in a 50:1 saw - that would be TWICE as much oil:gas ratio, not half... Steve

 

[arrow]

Uhh, Gary - he used 25:1 in a 50:1 saw - that would be TWICE as much oil:gas ratio, not half... Steve

He said "low oil ratio" (meaning numerically) not "low oil content" There's alot of controversy about fuel/oil mixes with increased oil causing "lean" conditions. ( with more oil causing less fuel to be burned) I'll let the smarter people argue that one out. What I have experienced when this has happened is a ring that has gotten so gummed up that it becomes stuck. You can try dissipating solvents like Marvel and Seafoam but usually if a ring is stuck, its stuck with nothing short of pulling the piston and reseating the ring will work.

 

[Egon]

Is the exhaust free and clear?

 

[cycle_gator]

I have had similar problems with my Stihl 50:1 saw and running "old" fuel ("old" being more than 6 months). Once I got good fuel in it, it still did not run right, until... I feathered the throttle until I got it running at max RPM and I let it run there for quite some time. After two or three times doing that the power returned. I am not sure if the rings were gummed up, or the reeds, but getting enough stress on it or fuel flow through it made it run correctly again.

 

[newbury]

Try mixing in, as suggested, Sea Foam or similar into ETHANOL FREE GAS then run thru a tank of fuel. Try to run it at idle and gradually increase and decrease the speed.

Before switching to eFREE my Stihls (021, 660, 660, 088) would "gum up" and run poorly or not at all. SeaFoam saved the day.

 

[luvmexfood]

I once put bar oil in the gas tank. To big of a hurry and not paying attention. Wondered why saw would not start so I quit for the day. Couple days later found the problem, poured the oil out and added gas/mix like it should have had. Started and no problems since.

 

[MotorSeven]

Believe it or not 25 to 1 leans the mixture and you might have scored the piston/cylinder. Pull the spark plug and the muffler, get a bright flashlight and inspect the inside of the bore and the piston/rings. If you see scoring, you will need at least a new piston & rings. If the aluminium transfer is not too bad on the cylinder it can be cleaned off using muratic acid and Q-tips(do not breath those fumes).

Scoring will look like this(the vertical lines on the left side of this piston):