Stihl Four Stroke

[Twinfield]

Is it possible to have a good leak down and Vac/Press test and still have carbon build up on the valve(s) that would cause poor acceleration. It needs a little throttle to get it started either with choke or not and will Idle all day, but when raising the RPMs wants to die out. I have replaced and/or adjusted everything I can think of shy of opening it up and looking at the valves. It's a Stihl 4180 series engine. Thanks.

 

[Burning man]

What elevation are you at? If it's reving to max rpm under load but tries to die when you give it throttle most likely the idle speed screw is set to low and you need more fuel from the low speed circuit.

If the valves look pretty carboned up that can can cause issues but are usually continuous once you get past idle. But clean valves mean a happy engine, a can of seafoam or chemtool will clean them pretty easy. Just put it directly in the ports and let it set.

 

[cscltd]

does that include replacement of carb?
oem or aftermarket?

 

[Twinfield]

does that include replacement of carb?
oem or aftermarket?

Yes, OEM CARB replaced