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J.R., Small Engine Technician
Category: Small Engine
Satisfied Customers: 7445
Experience:  Owner of outdoor power equipment business, repairing all makes and models.
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I have a Stihl 025 chainsaw with very low hours. The other

Customer Question

I have a Stihl 025 chainsaw with very low hours. The other day I was cutting up a pile of branches. The saw started as normal and ran great. A little while later I would set it down to arrange my cutting, then when I picked it up real fast it would kill. I would start it back up and it would run cut etc. Then I had trouble starting it. I thought maybe a spark plug. I pulled the plug and it was black and soaked with gas. I cleaned up the plug and got it to fire but it will rev, it is very skiddish on acceleration, and it won't stay running for long. I cleaned the carb. put new screen, diaphram and gaskets in the carb. It still doing the same thing. Any ideas on what it could be
Submitted: 7 years ago.
Category: Small Engine
Expert:  J.R. replied 7 years ago.
Have you checked the sceen in the exhaust?
Customer: replied 7 years ago.



The screen is clear. almost like new good flow

Expert:  Deere Dr replied 7 years ago.
Sounds like when you rebuilt the carb you got the metering lever to high.

The metering lever is the part that attaches to the needle and has a spring under it. This lever needs to be level with the base of the carb. Not the outer edge but the center area where the lever is attached.

After you adjust the lever and before you install the carb tip the saw carb mount down and allow any fuel in the crankcase to drain out. Remove the muffler also and do the same there.

Good luck.
Customer: replied 7 years ago.


The needle was wrong in my rebuild kit. So, I used the same lever needle and spring. It was carefully reinstalled back to where it was. I did no adjustments to it. I just cleaned the carb, put a new main screen back in and a new diaphram and gaskets.


Do you still think it was the needle?

Expert:  Deere Dr replied 7 years ago.
If it was the wrong needle that makes it even more likely the culprit.
Customer: replied 7 years ago.



The kit had the wrong needle. It was obviously 2 times longer and would have never fit, so, I used the old one.

Expert:  Deere Dr replied 7 years ago.
Did you check the height of the metering lever when you took it apart the second time?

Adjusting needles preset at 1 1/2 turns out.

When I am working on a saw that was flooded, wet plug, I pour out the fuel and try to start the saw with an empty tank. I know, sounds silly, but it will burn out any residue fuel in the crankcase.

Have you actually removed the entire muffler and looked in the exhaust port at the piston. If it is black below the rings you have a stuck ring. If the piston is scored you have a boat anchor.
Customer: replied 7 years ago.

I checked all of the things you mentioned earlier. Seems ok. The piston looks great on intake side and exhaust side. Also good compression. I had run it already without the fuel line hooked up to burn out the gas in the crank and I did try to spill out any gas from the crank. It would not start last night no matter what I did.


Here's the confusing thing. This morning I choked like nomal. It sputtered. I put it to run. And it ran like a champ. Great acceleration, good responsiveness. I ran it for a good 5 minutes Ideled great etc.


Then I was going out to cut wood put my jacket and bibs on. Took it outside and it would not start again. I'm about ready to take it to the Stihl dealer in town. I'm baffled!!!



Customer: replied 7 years ago.
I talked to a friend that works on chain saws. He suggested that I check the kill switch wire to make sure it is not broken or damaged thus grounding out the ignition spark. No such luck. It was in great shape no cuts or breaks. Still not running
Expert:  J.R. replied 7 years ago.
Did you compare the gaskets and diaprams in the new kit with the ones you took out. The correct carb kit should have had the correct needle as well.
Customer: replied 7 years ago.
the gaskets and diaphram were exact. there were quite a few items that did not match in the kit. I'll check with the shop on monday
Expert:  J.R. replied 7 years ago.
Let me know.