Stihl 026 pro starts and runs well for 10 min

[Fastfriend]

......I have a low hour 026 pro that I recently inherited. It starts Ok, runs and cuts great for about 10 minutes or so and then starts to fog on the top end and eventually dies. Because it runs so well at the beginning, and will restart and run again when it is cold, and seems to have a good "putt" to it when pulling the starter, I am assuming that my piston and cylinder are fine, and it doesn't run hot like it's really lean before it dies...it seems to just quit pulling fuel, even with the low idle screw backed out well beyond where it should be set..
....Sooo that leaves carburetion. I have not pulled the carb apart yet, because it runs so well when it does run...I did put a new fuel pickup line and filter on it, and I have checked the fuel tank breather. Still acts the same.
......So now I am thinking I may have a vacuum leak at the impulse line or intake manifold that might be opening up when the saw gets warm. Can anyone tell me if I am heading the right direction, and has enough experience with this particular model to know if these saws are prone to vacuum leaks and where........or if I should go back and tear the carb apart....

 

[Adirondackstihl]

http://www.arboristsite.com/chainsaw/198274.htm

 

[watsonr]

An air/vacuum leak would be high idle, not dying out. If it doesn't restart until its cooled down... its the coil. If its just not running very well on the top end after the ten minutes of running it could be compression is weak, check the piston for scoring. Also twist the fuel cap a little just as it starts to die and see if that helps, if so it's the vent line/cap. Could be the carb, but it wouldn't run for ten minutes and show its ugly side if it was. High speed doesn't have much to do with the low side adjustment.

try those first and then we'll go from there.

Welcome to the site.

 

[H 2 H]

Does it run fine with a full tank of fuel ?

I have a saw that had a pin hole right above the fuel filter in the tank when the fuel got below that pin hole it would die out after a few minutes just like your talking about

 

[jus2fat]

If the saw will start and run fine for 10 minutes or so...then dies and won't start...

But will start and run fine again after it cool off...only to die again when hot again...

You likely have a bad coil...that's where I would begin..!!

J2F

 

[fossil]

If the saw will start and run fine for 10 minutes or so...then dies and won't start...

But will start and run fine again after it cool off...only to die again when hot again...

You likely have a bad coil...that's where I would begin..!!

J2F

X2

When it dies, check right away to see if you're getting spark. I've seen a number of coils act up as soon as they get hot

 

[Fish]

A complete fuel system teardown/carb rebuild is the first place to start!!!!!

It should be done as regular maintenence, anyway.....