Stihl mm55 carb issue

[Bucky]

New to forum. I have had my mm55 for probably 5 years. Great machine. But just like my Stihl chainsaw, it seems that they are very sensitive to fuel issues. The mm55 ran great for the first year. Was a little tempermental the second year. Then in order to get work done we had to run it with the choke partially on. Now it doesn't run well even with that.
Yesterday I pulled the carb off, dissassembled and cleaned everywhere I could. I removed and inspected the fuel line, and didn't see any cracks or holes. I do notice that the primer doesn't come back up well now, but it seems primed. I think it actually runs worse now than it did before all of this. The gasket going to the air cleaner assembly tore slightly during disassembly. I wasn't able to get the high speed needle out to clean behind it because of the limiter, and didn't want to break it.
My saw is already in repair shop prison for repair for a week now. I need to get to the point where I can do these repairs, since the Stihl always seems to need it. Not bashing it, but they do seem fussy. I have no access to fuel without ethanol around here anymore. I am running fresh 87 octane with Stihl mix.
Any help is sure appreciated. I could use the help!:confused2:

Oh, I did remove the spark arrestor and inspect. It was by no means clogged, nor did it have all that much carbon. So I reinstalled.

 

[Mikel1]

Did you replace the air filter and fuel filter? Was the metering diaphragm stiff? Is primer bulb filling up, doesn't have to fill all the way up? The thing that makes these carbs difficult to clean is the one way check valves. Compressed air or carb cleaner can damage them, ultrasonic cleaning is the best way to clean these type of carbs imho. Most repair shops usually just replace these carbs because of their cost versus time dealing with the carb.

 

[Bucky]

I called the dealer, and that's what he told me too. So I bought a filter, gaskets and carb. Took them home, and 12 minutes later the thing runs like a top. I messed with that thing for over an hour yesterday.
I was so impressed, I bought a new fuel line for the chain saw M250 and a new carb. That one took longer, as the fuel line is a little unhandy. I don't think either of these pieces ran this good even new. I didn't even have to adjust the screws at all. The started right up, and idle nice. Maybe a little high on idle for the saw, which is an easy fix. Wife used the mm55 with the sweeper attachment to get rocks out of the yard from plowing this winter. I cut down a dead tree. I'm happy!:smile:

 

[Mikel1]

Sounds good