Ongoing Issue With Craftsman / B&S Push Mower

[Quarterwave]

Hi everyone,

My Briggs & Stratton powered Craftsman push lawn mower is giving me issues.

It's a Silver Series 500 model, rated @ 5.5 horsepower.

Basically, the mower runs very rough (low idle, sputtering) and is coughing out black smoke from the exhaust.

I have:

- Replaced the spark plug with a factory replacement and gapped it at 030. (manufacturer specs)
- Changed carburetor diaphragm with new replacement parts (correct parts matched to carb and engine type)
- Emptied tank and added fresh, non-ethanol gas
- Disassembled, cleaned and degreased the entire carburetor assembly (non-float type, that sits on the tank directly with 5 screws holding it in)
- Installed new spring and sending tube filter
- Added new air filter (with lightly applied oil)

Can anyone please advise what else it could be? Every post that I've read online says that the diaphragm should have fixed it.

Thanks!
Quarterwave

 

[tigercat]

Sounds like a carb issue like the choke is on or the carb is not metering the fuel properly.

I vote to replace the carb with a new one.

 

[Rivets]

Check section 3 of this manual, it may provide some help. I agree your engine is running rich, did you nstall the diaphragm and gasket in the correct order?

https://docs.google.com/file/d/0B6NaqjIxWV1ycG8wd0s3Z2Q2X00/preview?pli=1