tree removal - chaisaw problem, wrog fuel mix

[cnice37]

Whe was the last time the 359 was run? I don't think a poor mix run for a short time will hurt the saw so bad. Also, just mix 50:1 and run it in everything, modern oil is much better and will lube the old stuff just fine.

I'd suspect carb needs a rebuild if the saw sat with gas in it. Maybe fuel lines and filter. Pull the muffler and check what Moto7 said. If no scoring, stick a thin screwdriver in there and see if the ring is stuck.

Where are you in Mass? I'm in the Fall River / New Bedford area if you want someone to take a look.

 

[NS Gearhead]

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.

Same issue with my Sthil 250. The dealership cleaned out the carb a couple times and accused me of using old gas/ not running it empty after use. It happens after as little as three weeks sitting with fresh gas! I've found limmited success mixing marine ethanol Stabil, and carb cleaner in with my mix. Funny thing is that my Stihl Kombi can go a full three months and fire up first pull with full power. Very frustrating. My next saw probably won't be a Stihl because of this.

 

[Ken45101]

I try Seafoam any time there is a problem. Works most of the time. Run it for a bit, let it sit for a day, repeat as necessary.

+1 for sticking to a 50:1 mix with premium oil (Stihl, Husky) for all. I've been told the same, the new oils at 50:1 are great for the old saws.

 

[arrow]

Same issue with my Sthil 250. The dealership cleaned out the carb a couple times and accused me of using old gas/ not running it empty after use. It happens after as little as three weeks sitting with fresh gas! I've found limmited success mixing marine ethanol Stabil, and carb cleaner in with my mix. Funny thing is that my Stihl Kombi can go a full three months and fire up first pull with full power. Very frustrating. My next saw probably won't be a Stihl because of this.

Depending on how old this saw is with enough exposure to what I call one of the biggest hoaxes on the American people (ethanol), the diaphragm in the carb could be weakened.

 

[arrow]

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):

I've seen this with lean "air" fuel ratios. Never with too much oil ratios. My career saw everything from 16 to 1 to 50 to 1 gas mixes and with a crew of 8 guys, anything could happen with fuel mixes.

 

[JimRB]

I use Stihl oil. The orange or silver bottles and premium gas. All my equipment from a few Stihl MS saws, KM110, Hedge trimmer, Husky weed wacker, and an Echo blower all start the same even when sitting for months. Maybe something else is going on. For my Stihl engines I squeeze the throttle and flick to start/run. I do full choke. Pull a few times to hear a putter. Half choke and start taking it off half choke. The only time it does not work is if the diaphram gasket has dried out. This is the gasket that is part of the fuel pump circuit. If the equipment has a primer bulb I will press that a few times.


I have a Honda generator I bought used at least 3 years ago. I start it when I think of it. Gas looks ugly but it starts every time. Ever since I got it we have not had a power outage so it is doing its job.

 

[tractchores]

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):

Thanks. Would scoring of the piston cause the issues I'm experiencing? It seems to run fine at other speeds, but dies when given full throttle. Though yesterday I got it to run almost normal for a few minutes then start doing it again and now it stalls pretty much immediately. I'll take a look in the cylinder today and see what it looks like. This is a pretty old saw (90's vintage), so maybe that something else just decided to fail finally VS having anything to do with the fuel - though that's unlikely.

Whe was the last time the 359 was run? I don't think a poor mix run for a short time will hurt the saw so bad. Also, just mix 50:1 and run it in everything, modern oil is much better and will lube the old stuff just fine.

I'd suspect carb needs a rebuild if the saw sat with gas in it. Maybe fuel lines and filter. Pull the muffler and check what Moto7 said. If no scoring, stick a thin screwdriver in there and see if the ring is stuck.

Where are you in Mass? I'm in the Fall River / New Bedford area if you want someone to take a look.

Thanks. The saw was running perfectly before I put the wrong fuel in (like 2 minutes prior), so the only variable is the fuel. It had actually just been tuned up and has gotten regular use. I haven't checked the fuel line and filter (requires more disassemble), though that is probably the next stop. Thanks for the offer to look, I'm NW of Boston. I'll probably drop it off at my small engine guy if I can't figure it out today, he's pretty good and familiar with the saw.

Depending on how old this saw is with enough exposure to what I call one of the biggest hoaxes on the American people (ethanol), the diaphragm in the carb could be weakened.

I did check the diaphram, which looked ok. I was afraid it got gunked up with the oil. The saw didn't sit at all with fuel, so while I agree ethanol is evil stuff it probably isn't to blame here. I did put brand new higher test gas in it yesterday just to 100% rule out the fuel itself and had the same issue.

 

[LD1]

Is the exhaust free and clear?

Ditto that.

Check and see if you gummed up the spark arrester screen.

If that is good, I'd just keep limping through. Give it another tankfull of fresh fuel, and try to keep it running. Sometimes It just takes some time to flush all the bad mix out.

BUT......I still think there is a possibility that something else is going on here. 25:1 fuel for 1/2 a tank shouldnt hurt a thing in a 1990's vintage saw. When I rebuild a saw, I run the first tankful with extra oil. It isnt an exact science, but I add about a capfull of oil directly in the saw then fill with 50:1 mix. Smokes alot, I tune it pretty rich, run that tank out, another of just 50:1 rich, then tune accordingly. Never had any issues you describe in 20 some saws.

 

[Egon]

Same issue with my Sthil 250. The dealership cleaned out the carb a couple times and accused me of using old gas/ not running it empty after use. It happens after as little as three weeks sitting with fresh gas! I've found limmited successes mixing marine ethanol Stabil, and carb cleaner in with my mix. Funny thing is that my Stihl Kombi can go a full three months and fire up first pull with full power. Very frustrating. My next saw probably won't be a Stihl because of this.

Hmm; a couple of weeks ago my chainsaw started after the third pull after sitting four years with a half tank of fuel.

 

[tractchores]

I took it totally apart today, including the carb and block. Everything visually was fine, no scoring on the cylinders and everything was in great shape. The fuel system was clean and fine. The carb seemed ok, though the jets don't appear to come out so i couldn't manually clean them out though i soaked it in some cleaner. Exhaust was fine as was the air filter and intake...

Unfortunately once i put it back together it was exactly the same. I guess the next stop is the shop.

One last possibility is the fuel octane. I did switch to 93 octane for all my fuel (small engine mechanic claimed that would help it last longer), so the new fuel is that octane. Anyone ever heard of saws running poorly on higher octane fuel?