Need help with a 540xp

[Duce]

My problem is with this 540 that has been to war and climber uses it to make a living. Saw will start and run, but when it warms up will not hold idle and stalls. Saw has just under 150psi compression, holds steady vacuum. Have swapped out carb and ignition module from a nice running 540, saw runs the same. Spark plug on saw is black, nice running 540 is light brown. Can lack of cooling fins cause auto-tune to feed more fuel to saw, making it stall? Tell me what you think, besides auto-tune stinks. Thanks

 

[TreeLife]

It looks disgusting, like it needs a degreasing

 

[Duce]

Should have seen it before compressed air treatment. Will give it a cleaning if I figure it out. Look at repair job on chain brake.

 

[Derf]

Did you check the tank vent?

 

[Duce]

Yes. It's clear.

 

[weedkilla]

I'd be looking for an air leak. Auto tune doesn't compensate at idle.

 

[Duce]

I'd be looking for an air leak. Auto tune doesn't compensate at idle.

Thanks for the reply. Maybe leaking around intake plate, do not see any rips in boot. Holds steady vacuum. Will reassemble and spray with carb cleaner.