Stihl 036 possible seal leak?

[doc henderson]

you can run them all the way in and count your turns, or mark the slot in the screw with a sharpie, but that sounds unlikely.  i still am hoping for you it is something simple.  Please don't take this the wrong way, but it seems you are going for the big stuff.  So just refilling with fuel does not solve the problem, and letting it cool off does not solve the problem?  The fuel line as you probably know, is a molded engineered piece of the machine, that often gets a crack at the bend, that is hard to see, costs about 5 dollars to repair.  It is so common that my stihl mechanic told me after a description over the phone of the problem, that it was most likely the problem.  In fact his name is Sylvan at fairveiw service in Pleasant View, Ks if you want to give home a call.  Or better yet call your local dealer if they have a mechanic that does only Stihl power equipment for 40 years.  Trying to help!  Sounds like you have other back up saws as well.

[joe_indi]

Update. Ran the saw today and it is still doing the same thing, half tank of gas than needs to be retuned.........

Oh oh, I think what I typed was deleted by my over enthusiastic Keyone :(
What you mentioned above could happen if the tank vent is blocked. A low pressure will be created in the tank to the point that the pump is unable/difficult to draw fuel.
It's very easy to check this. When you reach the half tank level and the rpm starts playing up, just open the filler cap and then close it. This will equalise the pressure if the vent was indeed the culprit your saw should run normally again

[Jsawyer]

Sorry if I missed it...did you do a pressure test/ vacuum test? It should hold 10 psi and at least 6 or 7 inches of vacuum. I blocked off my 034 with some fender washers and and some 1/6 rubber. You can test thru the impulse line. I had similar problem with my 034AV thought it has seal leak but it was the Reed valves in the carburetor and the fuel line and filter.

[knuckledragger]

036AV, rebuilt the saw and had high idle trouble as well. This 036 never would idle down. I went through all the simplest causes of this symptom and all checked okay. Aggravated I put the saw on the shelf and there it stayed for close to 90 days. When I cleaned my bench off one day I decided to give myself another shot at being smarter than the saw. Turned out to be a leak in the crankcase via the seal on the flywheel side. I replaced the seals on both sides since I had the saw that far down. That 036 schooled me on saying out loud that I had rebuilt a saw that I really hadn't totally rebuilt. Oh, the 036AV was purchased shortly afterwards. The boy that bought the saw is still running it. I looked back to see when he got it, 11-18-2017.

[oldred]

if its runs normal cold then bogs down warmed up it could be ignition/electrical issues, fuel tank cap or incorrect carb adjustment. could be seals but it would run lean if the carb its properly adjusted for the big bore. 

throw in a new ngk bpm7a spark plug. test your coil. pressure/vacuum test your seals and cap. if you got it ripped down to the case, throw in some new seals theyre cheap and itll give you piece of mind.

[oldred]

..that is if i'm understanding you correctly. "bog" to me means its running rich or slowing down.
also if you havent rebuilt the carburetor, rebuild it. specially since theres a new top end on there, it has to be adjusted specifically to the bigger bore. 

[Cam460]

Alright guys so here's where I'm at I put a new set of crank seals in it thinking that solved the problem. The old seals were pretty brittle. So I re tuned it just to have the same thing happen the only thing I can think to do is a total carb rebuild. 

[Mad Professor]

Seals, intake, fuel line , vent all O.K.?

The carb ,besides rubber, can have things like a piece of crap in it. Besides a carb kit, not a chinesium kit, a sonic cleaning can get crap you'll never see out.

It's worth fixing, my 036 saws are my favorite for firewood < 20".  Pretty easy to fix in most cases. They are stihl all german parts.

[Air Lad]

Alright guys so here's where I'm at I put a new set of crank seals in it thinking that solved the problem. The old seals were pretty brittle. So I re tuned it just to have the same thing happen the only thing I can think to do is a total carb rebuild.

If you're going to pull the thing down the carb kit/impulse line/fuel line are things that are worth thinking about while you're at it
Just sayin

[oldred]

rebuild it entirely, not just the gaskets. dont worry about the welsh plug.

if it still dont work check to make sure you got the right spark plug then start testing everything electrical.

[wild262]

And make sure the plug wire is not arcing or touching the cylinder anywhere.  Did you ever check the coil?

[limbwood]

when you are about to give up, put saw under pressure and put it under water and watch for bubbles, small leaks hide sometimes.