OS 1.20 with pump
 

I have 2 fairly new 120's with a pump. Both share a similar problem.
The motors run fantastic "when/if" they start. If I let these motors
sit for a few weeks with or without after-run in them , it seems that
the carb won't get fuel. It will run out a prime but that's it. Is there
anything I can do to avoid this from re-occurring.

Regards
Roby

RE: OS 1.20 with pump
 

Before applying the electric starter open the main needle 1 turn more from its standard position. This will help priming your engine.

As soons as the engine comes alive start closing the main needle towards its standard position.

I have two OS 120 pumped engines and with this method I have no problem starting them.

Stelios

RE: OS 1.20 with pump
 

Older pumped O.S. FS-120 Surpass engines had a difficulty that if they sat for several weeks, the regulator diaphragm would dry out a bit. This caused erratic regulation for about four to six tanks' worth of fuel...at 14-16 ounce tanks.

When starting the engine, we always opened the throttle to full, put a finger over the air intake, and turned the engine in the forward direction until fuel would start to spit out of the exhaust port. With a muffler, we'd hear the juicy, spitting sound. We'd take our finger off the intake and let the fuel dribble out, and then turn the engine slowly by hand for several revolutions. We'd then apply the glow plug battery and prop the engine or apply the starter. With a good plug, good compression, and good fuel, we've rarely had an engine not start and run unless the pump just wasn't moving fuel. With those engines having a crankshaft-driven gear pump, they rarely didn't pump.

The new engines use a diaphragm pump, but starting works exactly the same, but the regulators don't dry out.

The main thing is getting the system primed. Choking the carb with the finger helps a lot in drawing fuel through the system. Once the system's primed, we've never had problems with fuel flow.