Briggs and Stratton running rich

[Harmony]

I have a 6.5 HP B&S Quantum edge motor (123K02) on a pressure washer. It is about 6 years old with low hours (maybe 15-20) It runs , but at full throttle it stutters some. pop.pop.pop...Intermittently. As well, my plug (around 4 hours on it) was sooty. It has a manual choke carb with no adjustment screws or diaphram. The air filter is very clean. I cleaned out the carb with the normal carb spray/ wire through the jets. It was fairly clean, and the jests were not clogged. I put it back together, drained and dried the gas tank and added fresh gas.. Installed a new plug. It is still making the popping noise. Inspected the throttle and choke plate, they are wide open as they should be at full throttle (no load from sprayer). Compression is 55-60lbs. If anyone has any ideas, I would greatly appreciate it. Thank you

 

[mechanic mark]

FAQ | Lawn Mower Safety Tips | Briggs & Stratton Post model xxxxxx, type xxxx, trim xx from engine. Are you using B&S OEM plug and gaping to specs.?

Results engine manual & illustrated parts list

Single Cylinder L Head Repair Manual

Replace spark plug with B&S plug & gap to specs., adjust valves per specs., this information is on page 9 in operators manual posted above in results, engine manual.
Engine Won't Start | Mower & Small Engine Repair | Briggs & Stratton FAQ scroll down to compression & read

 

[Harmony]

Thanks for the reply Mark. 123K02 0509 E1 06102659 is on the tag. The plug is a Champion RJ19LM gapped at .030 I found a little bit of oil at the bottom of the head where it meets the block. I am not sure at this point if it is residual from a spill; or maybe it is the early stage of a head gasket leak. I have cleaned it up and will run to verify. I don't have a leak down tester. Would watching how long the compression guage held pressure verify this?

Thanks again

 

[reynoldston]

Seeing has been sitting a lot maybe a valve is sticking.

 

[Harmony]

Thanks for the reply. I can see that both valves are opening and closing. I also rotated them a little with a screw driver to make sure they were free.

Thank again

 

[Harmony]

I checked the valves. The adjustment was perfect. I cleaned the head up installed a new head gasket and she is running perfectly. Even though I didn't see signs of leakage, the new head gasket made the difference. Thanks for everyone's help.