Stihl 025 Fuel Puddling Problem?

[Hinterlander]

I have a 9 year old Stihl 025 that has been a workhorse for me. I have never laid a wrench on the engine with the exception of air filters and spark plugs. This saw likely has hundreds of hours on it, but it still has plenty of compression and with a sharp chain and clean bar, cuts like an animal.

Recent problem has been with seems to be a fuel puddling problem. When I get the saw hot, then set it down idling for any more than 10 seconds, I get an off-idle hesitation that feels like the saw is loading up. I get a little puff of black smoke out the exhaust if I can get it off idle without stalling. If it does stall, it fires back up easily.

My experience with 2 strokes tells me that fuel has accumulated in the crankcase, and when the throttle is opened, the fuel is sucked through the ports into the combustion chamber and I get a momentary rich mixture. Outboards have a check valve in the crankcase to prevent this, but I don't think the saw does.

Has anyone else had this problem with a Stihl saw? Any maintenance I may have missed that caused it?

 

[Sandor]

I have an 025. Have you went through the carb adjustment?

I get an off-idle stumble when its not adjusted correctly. Last time - it was a quarter turn, counter clockwise on the "L" screw. Then reset idle. Also, did you remove the plastic divider so it sucks warm engine air for wintertime operation?

 

[Hinterlander]

Thanks Sandor -

I have not put a wrench or screwdriver on the powerhead at all since I bought the saw, which includes carb adjustment. All I've done to the saw is maintain the bar & chain, but I do that dilligently. This saw has been so predictable the way it runs that it's amazing. Always starts on the 4th pull, always the same. It has never stumbled once. However, last Sunday, I was cutting some oak in 20 degree weather, and it kept stumbling.

First I will replace the plug since I can't ever remember doing that (shame on me), then will try removing the cold air baffle under the filter housing. If that doesn't do it, I'll try the carb adjustment.

These saws are so darn good compared to any other two stroke I've owned that I start thinking of it as a home appliance and not the fine machine it is!

I had an old 031av that ran the same way until it lost compression. I gave it to my brother, who pulled the cylinder and found the piston skirts to be about the thickness of an aluminum beer can. He honed the cylinder, rebuilt the carb, replaced piston/rings & gaskets and the thing still runs like a clock.

 

[elkimmeg]

You did not mention the gass how old was it? There are times when mixing the oil even changing brands of oil will effect the saw's preformance.
In that case one sometimes has to adjut the carb richer leaner probably just a 1/4 turn either way Till the gas can is used up.
This is common. You also did not mention whether you had more exhaust smoke. I have 6 saws here I cannot have 6 cans od fuel one for each saw so either I use it up for one saw or adjust the carbs so all will run on the 2.5 gal of gas

 

[Hinterlander]

Hi Elk -

It is fresh gas, about two weeks old. I mix all of my 2-stroke 100:1 using Amsoil synthetic and go through two or three gallons a month using it in the saws, snowblower, weed whips and blowers. Nice thing about Amsoil 100:1 pre-mix synthetic is no plug fouling, no exhaust port plugging and no pisting ring land coking. If any of the gas starts getting old, I dump it in my truck and replace with fresh.

 

[KarlP]

I mix all of my 2-stroke 100:1 using Amsoil synthetic

Maybe your saw is just pissing out half the gas to get the 50:1 it wants? :-D

 

[Hinterlander]

Nine years of hard work and no engine problems - the synthetic oil works for me!

 

[elkimmeg]

things change in 9 years lot of vibration I think its a carb adjustment. Shoot it up with carb cleaner while you have the cover and filter screen off might as well clean the screen too. Stihl recomends 40 to 1 using their own or equilvant oil The syn oil allow for larger ratio. But things change with time, wear does occure you may not have 100% compression now could be 90% M eaning it still runs fine but not as good.

 

[begreen]

I agree with everything except the oil-mix. My Stihl manual says 50:1 as does the Stihl fuel oil bottle.

http://www.stihlusa.com/accessories/twocycleoil.html

 

[Sandor]

Hinter,

You could have had a carb icing issue since you were cutting in 20 deg weather.

Let us know what you find out.

I have had my 025 for about 5 years and it works like a champ!

 

[pinefarm]

On a saw that old this may not be a problem but, on newer saws, there is a screen on the exhaust outlet to prevent sparks from exiting. This is apparently the law in the West. Your dealer won't remove the screen but, if you are not in a high fire area, you could remove it yourself. Otherwise, remove it and clean off any carbon before replacing. It can cause problems if left unattended. Dave Johnson

 

[Hinterlander]

OK, thanks for the advice guys. I flipped the carb heater 180 degrees, warmed the saw then started working on a pile of chokecherry in about 26 degree weather. Ran about the same with the carb heat on, so I adjusted the low speed lean about a quarter turn as directed in a previous post. It ended up taking a half turn lean on the low speed adjustment to get rid of the off-idle problem, but I backed it a quarter turn from the benchmark to be safe (too lean means more heat). Runs much better (won't tell my wife that, I want a new saw!).

Also, checked the screen tonight. No problem there, clean as can be.

 

[BrotherBart]

OK, thanks for the advice guys. I flipped the carb heater 180 degrees, warmed the saw then started working on a pile of chokecherry in about 26 degree weather. Ran about the same with the carb heat on, so I adjusted the low speed lean about a quarter turn as directed in a previous post. It ended up taking a half turn lean on the low speed adjustment to get rid of the off-idle problem, but I backed it a quarter turn from the benchmark to be safe (too lean means more heat). Runs much better (won't tell my wife that, I want a new saw!).

Also, checked the screen tonight. No problem there, clean as can be.

Mark another one up for hearthnet.

Glad it is back to running good.

 

[Hinterlander]

It's amazing how much one can learn on these forums. There is an incredible amount of wisdom here, and my kind of people (chain saws and wood stoves all in one place? AWESOME!).