MS180C Strange Throttle Behavior

[kmcghee]

I was gifted an MS180C from my father in law. It had bad gas in it, so I did the following work to the saw:

1. Cleaned the tank,
2. Replaced fuel line
3. replaced fuel filter
4. disassembled the carb, scrubbed with WD40 (no carb cleaner available at the time)
5. Blew out all ports, jet,
6. Installed carb kit including new needle, spring and fuel screen,
7. Cleaned screen in muffler,
8. Blew out air filter.

The behavior I have is it starts fine, has a slightly high idle, but on wide open throttle it speeds up to what I think is WOT then drops down to idle then speeds up and keeps doing that. Sounds like its starving for fuel but I am not sure where to start.

 

[Brushwacker]

Is the throttle butterfly in the carb secure, not loose?
Might also try a new impulse hose ?

 

[coffeebrk]

What is the condition of the piston & cylinder? Post a pic. Did you set the metering lever hight correctly?
You could check for air leaks using the propane test.
I picked up a 180c a couple of years ago. I'm guessing it maybe had a few tanks run through it. It had similar running issues.
I assumed that it had the original OEM carb so I'd just put in a kit. It didn't have the OEM carb lol. I decided to put an after market carb in and it runs great.

 

[trains]

Is the throttle butterfly in the carb secure, not loose?
Might also try a new impulse hose ?

Impulse comes thru the intake boot, but yes, where the carb seats against the boot can have issues sealing, there is a spacer there too that can either be not put back, or move and cause issues.
I think you still have issues within the carb, and or the needle metering lever height is incorrect.

 

[epo]

Was the carb kit you installed OEM? And if so what was its part number?

 

[buzz sawyer]

Could this carb have an internal check valve that was damaged by blowing it out?

 

[trains]

Could this carb have an internal check valve that was damaged by blowing it out?

it wouldnt idle if that was messed up.

 

[stihltech]

Check fuel tank vent. Known to block especially with old fuel. Sounds like a fuel delivery issue. Are these OEM parts?