I have a 10 HP OHV Briggs & Stratton engine on a 5500 watt generator. It runs smoothly if the choke is about halfway closed but if I open it all the way the engine starts "surging". I did the same winter prep on both machines (I have two of them) & the other one runs fine. I put a small amount of fuel with some Marvel Mystery Oil conditioner in and I am letting it run until empty. My assumption is that I have a small jet or fuel passageway in the carb clogged & thinking this might disssolve / clear it up. I'm not sure if there is a needle valve adjustment to be made on this engine, there is a plastic cover partially obstructing full view of the engine. The only serial numbers I could find were for the generator, not just the engine. It does say "FAMILY 6BSXS.PT" on a sticker on the recoil housing. ny input is greatly appreciated!

TexasFire

 

Yep, it sounds like your carburetor has a jet or passage clogged. Generally additives in the fuel don't work well once the clog has formed. Without fuel flowing through the jet it is almost impossible for the additive to get to the obstruction. The best option is usually to disassemble and clean the carburetor.

 

Roger that. It seemed to run a little smoother after the fuel treatment but still required the choke to be slightly closed. With the choke adjusted as mentioned, it purrs smooth as silk. Does this hurt anything? I planto pull & clean the carb but it may be a bit before I can get to it....
Thanks!

TexasFire