MS 391 Too much fuel!

[Gilderbeast]

I have rebuilt my carburetor twice on my MS 391. I can not get it to idle. It only wants to run at high rpms which makes me believe it is getting too much fuel. I've gone from .5 to 1.5 on the low idle screw. 1.25 works best but will not stay running. I always have to start it with the choke on. I let it sit overnight and it filled the crankcase with gas. Does this sound like a bad needle and seat?

 

[ballisticdoughnut]

Do you have the metering diaphragm in the correct order? Gasket first, diaphragm second. If it’s reversed the carb will flood and saw won’t run right.

 

[Gilderbeast]

Do you have the metering diaphragm in the correct order? Gasket first, diaphragm second. If it’s reversed the carb will flood and saw won’t run right.

I have it just like the diagram.

 

[ballisticdoughnut]

You set metering lever to the correct height? If that’s good sounds like you got either a needle or seat problem. If it’s the seat your looking at a new carb.

 

[Gilderbeast]

You set metering lever to the correct height? If that’s good sounds like you got either a needle or seat problem. If it’s the seat your looking at a new carb.

Yes. I ordered a walbro rebuild kit this time and also a brand new walbro carburetor. I'm pretty positive it's the needle and/or lever out of adjustment.

 

[stihltech]

Do you know how to set the lever height? May not be correct by just assembling the kit.

 

[Gilderbeast]

Do you know how to set the lever height? May not be correct by just assembling the kit.

I do not know the spec or where to measure from.

 

[stihltech]

Now we have a place to start.

 

[SteveSr]

Do you know how to set the lever height? May not be correct by just assembling the kit.

The metering levers are NEVER pre-adjusted. Adjusting / or checking is part of the rebuild process.

I usually just reuse the old levers because the don't wear out but I ALWAYS check them since I may not have been the first one in the carb.