HELP! Trouble with a 266se

[av8or3]

Hey guys, maybe I need a car battery upside the head or something. This 266 passes the press/vac test after replacing the oil seals. It passed before replacing the seals , results just got better after. The pto side o-ring looked to have been cut/mashed the last time installed so I replaced that with one from another saw. It starts completely normal and after warming up a little it takes off (engine speed) and sometimes
can be adjusted to seem normal but it is not right. The last time I ran it I backed the L screw out till it was loose and it made no difference. Engine still raced. This is a Tilly HS and I’m no stranger to these things. Built a bunch. This one included. That’s why I have trouble believing it’s the carb. Thus one looks real good. The trouble started after cutting a whole bunch (8-9) 16” pines down and limbing them. Inside the carb I found a lot of clear nail polish that had come loose (around the welsh plugs) that certainly could cause trouble but I’m pretty sure I got it out in the USC. What in the hell (inside a carb) that can mimic an air leak?

 

[beaglebriar]

Worn shafts will do that. I’ve replaced a few carbs for the same reason.

 

[ErnieG]

Swap out carb with a known good one ?

Ernie

 

[Shane¹]

I had the worn throttle shaft get me one time it sounded just like a crank seal leak and I could not find it for the life of me

 

[Czed]

Did you check the intake block for cracks
Or warping
I had a couple that were hard to diagnose that way.

 

[Woodslasher]

Had an old 61 Rancher do that, the Walbro in it had worn out shafts. I had a good used Tillotson I swapped in and problem solved.

 

[drf256]

Are the shafts binding? The linkage?

Nozzle check valve being bad will allow the metering side to suck air in through the nozzle during idle/low speed operation instead of opening the needle for fuel. Can be intermittent problem. A common issue for uncommon carb issues.

Treemonkey used to say he never uses a USC on carbs. He felt that they could vibrate debris into some small passages and render the carbs useless.

I’d try another carb and check the linkage. Also, I’d check all the gaskets and intake block. The 266 has that strange intake block that bolts to the jug first, and then the carb bolts to it. They changed it out on the 272.

 

[av8or3]

Thanks everyone. Lots of good food for thought. For now I will take off the entire intake stack and have another good hard look at the carburetor.

 

[av8or3]

Well, seems that claiming to know something inside and out doesn’t prevent you from making mistakes. Found this right away. Hopefully it will fix the saw. Wife just got up so I’m out the door to find out.

 

[ErnieG]

That rascally spring !

Ernie

 

[av8or3]

That fixed it. Saw runs awesome again.
There’s more oil running out the bottom than onto the chain so, once it cools down I’ll recheck my oil o-rings.
Thanks for all the helpful hints. I really appreciate you ALL.

 

[av8or3]

Here’s an earlier mistake I uncovered. Thought it would fix it too.
Never too old to learn.