Stihl 026 chainsaw - no power

ejb · Sep 7, 2005

I have a 15 year old Stihl 026 chainsaw...its been a great saw and seen a good amount of use...much more than an average homeowner I would guess, but not nearly as much as a logger.

It started running badly this year so I changed the tank to fresh gas, put a new chain on it (which I usually do every 1-2 years) and cleaned out the air filter and new spark plug(which was pretty bad).

Starts up fine now, accerelates fine, but when under power it smokes like crazy and has not much power at all...can barely cut a tree without a gas mask on /forums/images/graemlins/ooo.gif

My guess is a carb adjustment...but which one? With these symptoms, is it getting to much gas, or not enough? starved for O2?...is it asking too much of a 15 year old saw, or do they pretty much run forever?

SkyPup · Sep 7, 2005

They run forever.

I have a 25 year old 026 Pro that has seen unreal hours of heavy duty use. I tried to trade it in on a new 028C this year but the folks at the Stihl shop told me it would be a crime to trade it in as they last forever, so I kept it and got a new O28C too!

I suggest that you make some new fuel using fresh gas and full synthetic 2-stroke oil, and gap the spark plug.

You'll need a tachometer to set the high rpm carb setting and the low rpm setting (make sure the air filter is clean or new too).

If that does not work, do a compression check on it, it could need new rings if they are worn or have lots of gum sticking on them, howver a fresh tank of gas and good synthetic two stroke oil will clean that up.

slowrev · Sep 7, 2005

Muffler some clogged up ? Will cause power loss and smoking.

Ben

RobertN · Sep 7, 2005

You've checked some of these, but here's my list /forums/images/graemlins/wink.gif

Dump the tank
replace fuel filter in the tank and check fuel hose
refuel with FRESH PREMIUM gas and good quality mix
Clean or replace the air filter
Put in a new plug; check gap before installing
Remove the muffler
Clean the muffler
Clean and/or replace the spark arrester screen

Blow out the cooling fins and stuff whle covers are off too...

What mix are you using, and at what ratio? Stihl and Husky both make excellent 2-stroke mix. Mix as noted on the container; Husky mix is formulated for 50:1. I only mix a gallon at a time. I always use premium(these are high perforamnce 10,000rpm motors after all). I buy the little bottles of Husky oil that are made for mixing one gallon. 2-stroke mix degrades after mixing with gas. Remember it's a 10,000rpm engine; degraded lubrication is bad for it. I know of motocross dirt bike racers that use thier gas with 12-24 hours. Longer than that, and they won't run it in thier race engines...

It sounds like you have old mix, or the mix is at too rich a ratio. Either that or the spark arrester is too clogged to run at high rpm. Or, a mixture of both problems...

You could mess with the high speed jet. Try turning it 1/4 turn either way and see if it clears.

Kits are availble for carbs like that. I got one for an older Husky for about $15. Wound up replacing the carb; it was only about $75.

DrRod · Sep 7, 2005

RobertN brings up an oft overlooked point -- chain saws need high octane gas. I have an 026 and the manual says 91 or higher. I'll bet only 1 in 100 users has ever read this or follows it.

MikePA · Sep 7, 2005

chain saws need high octane gas. 
I just bought a Stihl string trimmer (4 cycle engine that uses a gas oil mix) requires premium gas, too. My dealer made a point of mentioning this several times.

bczoom · Sep 8, 2005

ajb,

Any update/fix?

If we're taking bets, I'm going with slowrev (and others) that think the muffler may be clogged.

One other thing that I didn't see mentioned was to avoid using 2 cycle oil that is made for marine applications. Don't recall exactly but do recall that it's a no-no.

Brian

PineRidge · Sep 8, 2005

My Stihl started doing the same thing so I took it into the shop for repair. There was a stainless steel screen in the muffler that was plugged. It now runs like new. Check to see if yours has the screen and make sure it's clean.

RobertN · Sep 8, 2005

Air cooled 2-stroke mix and water cooled mix are different because of the higher heat involved with air cooled engines.

A few years ago, I had rode rode my dirt bike on a Saturday. I mixed premium gas with a high grade racing 2-stroke mix. I had a gallon or two left over at days end. Went wood cutting the next day. Decided to use the gas mix from the dirt bike. My saws would start, idle, and rev without a load. As soon as I started to cut, no power! These were good running saws, using a premium motocross racing mix /forums/images/graemlins/shocked.gif

I gave up, dumped the tanks on the two saws. Went and got fresh premium gas, and mixed with chainsaw mix. Both saws ran great and cut like crazy.

Go figure /forums/images/graemlins/crazy.gif

SkyPup · Sep 8, 2005

I been using Amsoil's Full Synthetic 2-stroke motor oil in my three dirt bikes, six chainsaws, two weedeaters, and two outboards for years now, works great in everything.

ejb · Sep 8, 2005

Thanks everyone for all the suggestions. Glad to know this 026 can crank out for another 10 or more years...these saws aren't cheap.

Anyway, looks like the clogged muffler screen was the correct answer to the question; I already had fresh gas and a new spark plug, but didn't help at all. A good cleaning of the muffler and screen seem to do the trick...so thanks for that suggestion.

BTW: I used gasoline to clean it out (after removing from the saw)...is the a better/safer product to accomplish the same thing?

RobertN · Sep 8, 2005

A little Gunk parts cleaner(or similar product), and a toothbrush works. Then blow it out with compressed air.

Or, use diesel. Diesel has a much higher flash point than gas, so the chance of it igniting is much less.

Since I got my EMT certs while I was a volunteer Fire-fighter, I have always had a box of diposable latex gloves around. They are handy for that kind of work, so your hands are not in the icky stuff.

That excessive back pressure is a doozy; Diagnosis: Chainis sawous Constipationous /forums/images/graemlins/grin.gif

bczoom · Sep 8, 2005

( Anyway, looks like the clogged muffler screen was the correct answer to the question

Glad to hear it was a cheap fix. Consider everything else you did to it either preventative maintenance or just a good tune up.

Brian

Michael_E_Tx · Sep 8, 2005

Just a suggestion: If your spark arrestor screen was plugged, it is also possible/probable that your exhaust port is carboned up as well. If you have the muffler off, check the port to see if it is it's original size, a restricted exhaust port will also really affect performance.

Mike

SkyPup · Sep 9, 2005

I tossed the muffler screen on mine decades ago.....screams allot better without it. /forums/images/graemlins/wink.gif

RobertN · Sep 9, 2005

Be careful out there... It is not a muffler screen, it is a "spark arrester screen". Watch it in dry condidtions...

FBBSBG · May 16, 2011

I had a similar problem with my 1984 vintage Stihl 024. It started running fast then slow, almost like the gas tank was nearly empty with no power. In the past I've had to clean to exhaust screen and that helped, but not this time. I also cleaned the air filter, but it didn't help.

Since it was acting fuel starved, I took the fuel pump cover off and - low and behold - it had a lot of sawdust just under the cover. Looked like enough sawdust to keep the membrane from vibrating freely.

There is a small air hole on the cover that allows the air pressure to equalize, but I'm still puzzled how so much sawdust got under the cover. Could it be an air leak in the membrane that I could not see? Anyway, I didn't break the seal, just cleaned the sawdust out and it runs like new for now. Hope this helps anyone with a similar problem.

williekioti · May 31, 2011

I know this is an old thread, but since it was dragged to the surface......

A good method for cleaning a clogged spark arrestor screen instead of using volitile liquids; place screen in a pair of vice grips. Heat it up with a simple Propane torch till hot. Then brush off with a small steel or bronze wire brush. Let it cool, then re-install. Done.

FBBSBG, that membrane is your metering diaphram and yes it needs to be able to move freely with with changes in pressure. It opens/closes the needle valve allowing fresh fuel mix from the tank into the carb. With time and cutting with dull chains too often the fines can accumulate in there to restrict movement. Best advice? Keep your chain sharp so you're throwing bigger chips and blow out the airbox (not just the filter) once in a while. Good luck.

D7E · Jun 1, 2011

DrRod said:
RobertN brings up an oft overlooked point -- chain saws need high octane gas. I have an 026 and the manual says 91 or higher. I'll bet only 1 in 100 users has ever read this or follows it.

We cut hundreds of cords a year and have always used cheaper or dyed farm gas in all brands of saws including ( 2x 026 and 2x ms260's) and most of which are many years old now with no problems .

RobertN · Jun 12, 2011

They'll run on regular.

I run premium, based on inputs from a friend who is and arborist. He figures these are 10,000+ rpm motors. They are like miniature race engines. So he runs hi grade gas and oil.

D7E said:
We cut hundreds of cords a year and have always used cheaper or dyed farm gas in all brands of saws including ( 2x 026 and 2x ms260's) and most of which are many years old now with no problems .