Chainsaw carb adjustment issues

Hi all, hoping someone with two-stroke experience can help me out. I recently picked up a used Stihl 026 chainsaw and this carb has been giving me problems since day one.

Guy I bought it from rebuilds Stihls and Huskys, and said the only thing he hadn't gone over/refurbished was the carb. Everything else was mint, no cylinder scoring, etc. When I first ran it, it started spewing fuel. Quickly found out the fuel pump cover had an odd chip in the side, so he replaced it for free and solved that issue(may or may not be relevant). Put the carb back in, adjusted the H and L jets to about 1 to 1-1/4 turns out(it's got a ported exhaust so a little more than the standard 1 turn). Got it started up and adjusted them accordingly, slightly ROP at both idle and WOT accordingly. Runs incredibly well and responsively with plenty of power.

The problem I'm having is that she HATES cold starts. Even yanking away at full choke, I can never get it to kick over until I manually prime it by dribbling some fuel down into the carb(no primer bulb). Then it fires right up and runs great. Which tells me it's getting good spark, just not pulling enough fuel. It cranks right up when it's warm though, such as when stopping to fill the tanks, long as I don't let it fully cool.

Any ideas on what the issue could be? The fuel line looks good and tank is full. Checked to make sure it wasn't under vacuum. The impulse line looks good as far as I can see, though it's a PITA to fully access without tearing the entire powerhead apart. Hoping someone can tell me I'm missing something obvious, or at least point me in the right direction. Never had this much of an issue with starting on an otherwise good-running engine.

Brainstorming note: I have a brand-new spare chinese carb I can toss on it if there are no other glaring issues. Only other things I can think of is maybe a leak in the choke(which is just a flapper integrated into the air filter for some reason). Beyond that, maybe timing is outta whack? I dunno, just kinda spitballing while sitting here at work.

 

Did you ask these same questions to the guy you bought it from. Since you stated he rebuilds these saws -- it seems to me like he may have a few guidance points, unless he was hiding an issue to get it out of his sight?
Sorry, I know this ain't much help, but I have the luxury of a very reasonable (cost) Stihl dealers service dept. therefore I never mess with the adjustments on any 2-stroke. Good luck - there is probably someone here that is a wizard with this model of Stihl even though it has a few years on it.

 

Got the same problem with an 038. I'll keep an eye on this thread.

 

any update on this? @risethewake

 

Oh hey, i forgot I posted here lol. No real update unfortunately. Haven't needed to use it as much as I expected, and the saw runs fantastic otherwise so I've just been putting up with having to manually prime it to start. Eventually I'll get it back on the operating table and check for any minor leaks in the crankcase or intake, maybe just throw a new carb on it. Tried rebuilding the current carb, no change in behavior. I'll remember to post if/when I find anything worth noting.

 

i dont have that model but i do rebuild and mod saws for fun. I was just curious.

 

Check the impulse line.

 

Random update in case anyone's still curious:

Ended up trying a new carb today and found the root of my starting issue. See, the carb was held on by two nuts on the long studs coming outta the case. There were seemingly matching indents on the filter, which mounted on the same studs, so i figured it was just a little bit of weird overkill in design, to keep the carb secure when the filter is off

BUT..upon closer inspection, i found those nuts didn't allow the filter to seat correctly on the carb. In fact, they did not fit into the insets on the filter and left about a 1/8" gap between the carb and filter assy. Being that the choke plate is built into the filter, no WONDER it wouldn't start without me dribbling some gas on the filter to manually richen it.

Now that THAT mystery is finally solved, tempted to throw the old carb back on and probably see that it's just fine. I'd rather run the Walbro than the cheap Amazon knockoff anyway, it's being real finicky while trying to dial in the mixture.

 

Had the original Tillotson carb rebuilt (paid for, in a shop) and starts and runs great now. Full choke until it fires, then bump down for warm up. This saw hadn't been used for years, now it's one of 4 always used. Dull, or out of gas...grab another saw until you run out of saws.