Stihl 026 Air leak or carb ?

[ZeroJunk]

So, it will sit and idle perfectly. Make a few cuts and next thing you know it is taching 14,500 no load. And, it will settle right back down and idle perfectly.
It has that useless fixed jet carb with no adjustment, not available anymore, luckily probably. You can still order the adjustable version, which I did. Along with crank seals, which I have somewhere but they are alluding me at the moment.
I'm betting it's the carb since it idles perfectly. If I'm wrong I'll come back and eat crow.

 

[pioneerguy600]

WT 194 for the cure, OEM only.

 

[cscltd]

check your air boot- may have a tear that opens out when cutting?

 

[ballisticdoughnut]

Just went through a 026 myself. Genuine Walbro WT-194 is a must. Fuel hose, filter, pulse hose, crank seals. Check the intake boot. If it’s torn I’d be looking at AV mounts. Beyond that cylinder gasket and/or case gasket could be source of air leak.

 

[stihltech]

026? 20 plus years old? Vacuum and pressure test a must. Fuel tank vent open. Fuel hose not leaking or mushy. Do the the free checks first before you fire the parts cannon. Diagnosis can save a lot of money.

 

[bwalker]

14500 isn't that high for a 260. Muffler modded with a WT194 mine like 14800.
The max no load spec is 14000 according to Stihl.

 

[pioneerguy600]

Mine run over 15,000 but there is a lot of port work involved. The 026 and MS260`s like a lot of transfer tunnel opening and port extending/ redirecting, it is what holds them back stock.

 

[bwalker]

Mine run over 15,000 but there is a lot of port work involved. The 026 and MS260`s like a lot of transfer tunnel opening and port extending/ redirecting, it is what holds them back stock.

The carb and intake too. Stock the choke really restricts the carb. I trimmed all my 260 chokes.

 

[pioneerguy600]

The carb and intake too. Stock the choke really restricts the carb. I tried all my 269 chokes.

The airfilters on mine are milled to allow much more airflow, I run the fine mesh filters off the MS260 on all of the ported 026`s. The mufflers are opened to allow for all the extra airflow.

 

[ZeroJunk]

14500 isn't that high for a 260. Muffler modded with a WT194 mine like 14800.
The max no load spec is 14000 according to Stihl.

Maybe so, but the man said it was cutting off in the cut. Whatever than means. Also, it was more like 14,800 and would have likely hit 15 if I hadn't had enough.
Not my saw, so I will tame it down one way or the other.

 

[bwalker]

Maybe so, but the man said it was cutting off in the cut. Whatever than means. Also, it was more like 14,800 and would have likely hit 15 if I hadn't had enough.
Not my saw, so I will tame it down one way or the other.

FWIW those fixed jet carbs ran really lean. Could be an air leak or not.

 

[president]

Just went through a 026 myself. Genuine Walbro WT-194 is a must. Fuel hose, filter, pulse hose, crank seals. Check the intake boot. If it’s torn I’d be looking at AV mounts. Beyond that cylinder gasket and/or case gasket could be source of air leak.

top av mount on a 026 failure is common, and often leads
to torn intake boot !

 

[ballisticdoughnut]

top av mount on a 026 failure is common, and often leads
to torn intake boot !

Yep. Just rebuilt a 660 with a intake boot leak. Surprise surprise, upper AV mount was bad. Needed more than a boot and AV mount but nonetheless it’s now back in service.

 

[bwalker]

top av mount on a 026 failure is common, and often leads
to torn intake boot !

The AV mounts on the 026/260 are very soft. I've replaced them with 044/440R parts

 

[thompsoncustom]

Mine run over 15,000 but there is a lot of port work involved. The 026 and MS260`s like a lot of transfer tunnel opening and port extending/ redirecting, it is what holds them back stock.

The carb and intake too. Stock the choke really restricts the carb. I trimmed all my 260 chokes.

Indeed the stock intake/carb really holds them back when ported. I run a ms460 carb, 038 boot, velocity stack setup on mine (avatar pic) but have never put a tach on it to see how high the rpms are but it's up there for sure.

 

[ZeroJunk]

A lot of times you can see a crack in the intake or impulse with a good flash light on these type saws. There will be a wet spot or line in the dust.
I have fixed several saws with cracked manifolds, more with cracked impulse lines. They usually don't run worth a crap. This one runs fine, it's just too lean. I actually brought it home and cut some pecan.
I had a MS 660 with a stick stuck through the manifold, and a 200 or 201 with a stick inside the carb holding the butterfly open. How did they do that LOL.

Anyhow, if I can tune it to suit me with the WT194 I'll charge him $10 and the cost of the carb.
Getting in to anything else goes to $65 and hour. Not me, the store.

I'd bet this saw has never had 10 tanks of fuel through it, if that. Just another old man like me .

Hopefully Stihl actually has the carb in Hillsborough and I'll get it first of the week.
We'll chase it down eventually.

 

[Vintage Engine Repairs]

I’d suggest p&v test before buying a carburetor and seals. Right now it’s all guess work and may get expensive in time and money otherwise.

 

[ZeroJunk]

I’d suggest p&v test before buying a carburetor and seals. Right now it’s all guess work and may get expensive in time and money otherwise.

I will replace this non adjustable carburetor regardless.

 

[bwalker]

I will replace this non adjustable carburetor regardless.

That's a good idea and it's what I would do.
From the sounds of things the carb is just too lean, which almost all of those fixed jet 260 carbs were.
Although a P and V check isn't a bad idea.

 

[farmer steve]

check your air boot- may have a tear that opens out when cutting?

Had one acting kinda like that. When I went to pull the carb the clamp was loose on the boot.