026 impulse question

[kam]

I just bought my first Stihl chainsaw, a used 026. The gas tank is clean , pickup filter is clean, fresh premium gas and Esso 50:1 "synthetic blend",air filter is clean,spark plug cleaned and gapped at .020 (will replace when I get my order from Baileys). It idles but bogs down and dies when I pull the trigger ( jets temporarily at about 1 turn).

I'm down to checking the impulse circuit. I notice that the Walbro 194 carburator ( this model is not one of the carb options listed in the Stihl parts list for the 026), has a hose barb coming out the back of the carburator and plugs into the impulse hose "stub" coming out the housing. When the carb is seated, very little of the barb is inside the impulse hose (about 3/8' of barb is exposed). Is that normal? It looks
like a very poor seal.

I tried the shaving cream trick, smeared it over the barb and hose and don't see any of it disappear. What's next?

Kam

 

[Lakeside53]

The impulse connection is normal. The WT194 is a correct carb (and one of the best) for the 026.

Check your:

- Fuel filter (just replace)
- fuel hose
- Impulse hose
- carb inlet screen
- carb diaphragms, particularly the metering diaphragm.
then

Crank seals, flywheel side... but if it starts normally this probably isn't an issue.

 

[kam]

fixed today.

Found a hole in the impulse line...replaced it and everything is running fine. Thanks to Lakeside53 for his help.

Now on to the muffler mod.

Kam

 

[jp hallman]

Kam, might as well replace the fuel line and filter too.

 

[kam]

too late

"Kam, might as well replace the fuel line and filter too."

Everything's back together again. The fuel line is easy enough to do later,when it's necessary.

One thing I should mention to make it easier for others to diagnose.I p & v tested the crankcase to show the existence of a leakI could not see the leak even using soap bubbles or shaving foam.I put compressed air at 6psi in the impulse line on the carb side. I heard a leak , but could not see it. I then sprayed WD40 in the impulse tube.The liquide came spurting out the line about 1/2" behind the housing. Voila

 

[jp hallman]

Sure, one day you'll turn the saw it it's side to make a cut and then upright to buck or limb and the fuel line will crack and...viola! Won't run again. Of course this will happen when you're trying to outrun the daylight and finish a job you want done. Always seemed to me if one little rubber line cracked, they all did close together in time.

 

[Lakeside53]

Sure, one day you'll turn the saw it it's side to make a cut and then upright to buck or limb and the fuel line will crack and...viola! Won't run again. Of course this will happen when you're trying to outrun the daylight and finish a job you want done. Always seemed to me if one little rubber line cracked, they all did close together in time.

I find the impulse and fuel to be on different schedules for replacement.. One is affected by heat and the other by gas... and often years apart.

Being a Stihl tech, it way too easy for me to replace everything in sight; some of the customers are happy you did, but most are just plain grumpy about it. I evaluate the hoses - it they are "hard" or show white fracture marks when stretched, it probably time to replace them. If they leak at the tank, no question. If they break off when you pull on them to replace the fuel filter, the answer is obvious..

The impulse hose is exposed to the full cylinder heat cycles, handle/engine AV movement, and usually goes first. The fuel line is affect by gas but if the gas is a high grade (no alcohol), and not stored on the saw for long periods, they last a long time.

More...
Not all fuel hoses are created equally. Old 028 hoses "melt" in the tanks, 025 and 029 hoses turn to chewing gum and breakdown in sunlight (it gets in under the bottom of the air filter cover) and takes out the exposed part. Most of the hoses have been updated over time, and even the 026 in question has a newer style (the "bend in tank" version) for the old tanks.

 

[jp hallman]

"Being a Stihl tech". Aren't we talking about Husqvarna saws? I'm just speaking from my experience with Husky saws. Don't want to step on toes. What's a fuel line and filter cost? Ten to twelve bucks?

 

[Lakeside53]

"Being a Stihl tech". Aren't we talking about Husqvarna saws? I'm just speaking from my experience with Husky saws. Don't want to step on toes. What's a fuel line and filter cost? Ten to twelve bucks?

The saw in quesiton is a Stihl 026, and the fuel line only costs $7.30, but so does a six pack

 

[jp hallman]

The saw in quesiton is a Stihl 026, and the fuel line only costs $7.30, but so does a six pack

My mistake, expensive six-pack. Beer is belly wash anyway.