Stihl 026 Struggles

[sritzau]

Hi,

I have a Stihl 026 that I have used pretty steadily since about 2002. Lately the saw has picked up the annoying tendency to all but quit when you give it gas to make a cut. It idles OK, but when you give it gas to get ready to make the cut it first picks up speed and then dies off. Eventually it oscillates between running at close to normal speed and at very slow speed, and it will do that even if the saw has essentially no load.

I have had some suggest that the problem is a clogged tank vent, but even if I crack the tank when the saw goes into this mode it doesn't affect the behavior. I have ended up getting a second saw ( a Husky 455) so that I can keep cutting while I figure out and fix the 026. The 455 is a fine tool for moving wood, but I would like to have my 026 back.

Any suggestions of things to check as I take the 026 apart? To me the surging behavior - where the saw oscillates between slow and full speed - seems likes a pretty conspicuous symptom for people who know 2 stroke engines. I just happen to not be one of those people.

Thanks in advance,

Steve

 

[THALL10326]

Hi,

I have a Stihl 026 that I have used pretty steadily since about 2002. Lately the saw has picked up the annoying tendency to all but quit when you give it gas to make a cut. It idles OK, but when you give it gas to get ready to make the cut it first picks up speed and then dies off. Eventually it oscillates between running at close to normal speed and at very slow speed, and it will do that even if the saw has essentially no load.

I have had some suggest that the problem is a clogged tank vent, but even if I crack the tank when the saw goes into this mode it doesn't affect the behavior. I have ended up getting a second saw ( a Husky 455) so that I can keep cutting while I figure out and fix the 026. The 455 is a fine tool for moving wood, but I would like to have my 026 back.

Any suggestions of things to check as I take the 026 apart? To me the surging behavior - where the saw oscillates between slow and full speed - seems likes a pretty conspicuous symptom for people who know 2 stroke engines. I just happen to not be one of those people.

Thanks in advance,

Steve

That sounds like your getting a restricted fuel flow. Doesn't take much to make it idle but it needs fuel to run. Check your fuel filter first. If ok check the fuel hose. Hoses over time tend to get soft in the tank and can close up under full throttle. On the 026 that fuel hose takes a bend under the carb where it hooks up. I've seen many fold in that bend and restrict fuel flow to the point the saw acts just like yours. Check that hose..

 

[Mad Professor]

If it is like other sthil carbs I've worked on the diaphragm in the carb has a vent under the cover. It can fill with saw dust and prevent the diaphragm from working/pumping.

What I mean to say is the dust gets under the cover, between it and the diaphragm, then it stops pumping.

 

[Lakeside53]

Pressure test it.. then you'll know if it's NOT seals or a crankcase leak...

 

[sritzau]

If it is like other sthil carbs I've worked on the diaphragm in the carb has a vent under the cover. It can fill with saw dust and prevent the diaphragm from working/pumping.

What I mean to say is the dust gets under the cover, between it and the diaphragm, then it stops pumping.

Can you tell me how to check that and/or clean it up? Do I have to take the carb out?

Thanks,

Steve