MS180 Starts but does not run.

[bec98x]

I have an MS180c. That is giving me touble.

Unit sputers after 2-3 pulls on choke. (Normal)
Unit starts, revs up a little and dies out. (Does not rev up as normal.)
If you try to start again it will not start. You have to go back to choke and start all over again.

I have adjust the carb in and out in small and large amounts with little luck. I can get it to idle but when I pull the throttle it begins to rev up and dies.
I have even changed the carb with another one and still no luck.

If anyone has suggestions please let me know.
I will try to change the ignition system later and also check the crank seals.

Compression is around 140.
Flushed fuel tank and using fresh fuel.
Tested ignition with a spark plug tester. (With new plug) tested ok.
Checked fuel line for cracks.
Replaced fuel filter.
Throttle choke linkage ok.
Exhaust screen and port clear.
Found out carb was rebuilt a few months ago.
Opened carb. Looks clean.
Fuel pump diaphram looks clean and flat.
Metering diaphran was nice and soft. Tried changing it anyway.
Fuel screen clean.

[lawnscrape]

Sounds like an air leak.
How old is it?
Any chance the crank seals are bad, or the carb isn't bolted down tight?

[bec98x]

very sure it was bolted down tight. had it on and off about 5 times. each time had the same problem.

I did pressure test the carb and it held so no leaks in gaskets and check valves holding.

I did also check the impluse by putting grease into the hole and watching it blow out. there is no gasket behind the carb just the rubber boot thing connecting it to the cylinder.

I will check that as well as crank seals

[topsites]

I'm wondering if it could be shorting on one of the ignition switch wires,
to test this you might disconnect one or both of the wires leading to the
coil thus leaving the connection open.

Keep in mind if it works you'll have to use the choke to shut it back down.
Worth a shot IMO

[rotti1968]

If you can, pressure and vacuum test the saw, since your tried a different carb and you can get it to idle I would lean towards an air leak. Do this after checking the wires as was mentioned above. You have good impulse just by pulling the recoil over but when that thing is getting warm and you hit the throttle those cranks seals could be leaking. Also check that plastic sealing ring behind the carburetor and intake boot and make sure thats not cracked or broken and allowing air in.

[epicklein22]

Did you try a known good carb? I have made the mistake of trying other carbs and not knowing if they work. It can make you head in the wrong direction quickly.

You also really need to clean the carb completely. While they may look clean, there are a lot of small passages that you can't see where it goes and turns. Take each side apart, take out the needle, remove the float, and shoot brake/carb cleaner in ever hole you find. Let it dry (don't use compressed air to dry/clean the carb, you can damage it internally) and reassemble.