Stihl 038 upgraded, faulty seals?

[Jvision]

Hi there,
Great site, great advice, found everything I've needed so far.
Got an old 038av with magnesium tank and 24" bar. (you guys helped me ID it last year)
Upgraded it to magnum with 52mm pot from Farmertech, and did a muffler mod.

Runs fantastic - strong and fast - using it for cutting dead hardwood trees for firewood. (still need to improve my hand sharpening !)

Developed a problem...
Starts from cold one two three pulls, cough. Choke off, pull and zoom she's running. Cut, cut, cut no problem.
BUT between cuts sometimes there is a bogging down like fuel starvation. Runs fine on wide open, cuts strong, but will stall on idle occasionally. Pull the cord, starts easy again and runs - but might just die or run weak. Jiggle the throttle and it can be made to rev up (60% chance). Replaced the carb with Bing copy - no change.

I suspect leaky crank seals?

Don't have the tools to do a vacuum check or pressure test crankcase and local Stihl shop only likes the new stuff (and modded gear frightens them!)

Currently I have idle screw set high to reduce the problem - past where chain moves.
(BTW on finishing a cut I let throttle go and saw runs down slowly, chain whizzing along for at least 5 secs)

Any advice?

 

[merc_man]

Does the idle of the saw change if you turn saw upside down or on it sides. If so air leak.

Also could try spraying wd 40 or carb cleaner near crank seal and see if idle changes.


Sent from my SM-J320W8 using Tapatalk

 

[blsnelling]

Sounds like a carb tuning issue to me.

 

[Mad Professor]

Bogging coming off idle is usually too lean Lo setting.

Turn idle back down then try richen up Lo on carb.

Set idle so chain don't spin. Turn Lo in until it races/dies (lean) , then back out until it dies (rich). Set Lo halfway between, reset idle. Repeat.

If saw now bogs coming off idle, turn out Lo to make richer.