Old(brand new,never run,had it for years.)OS pumped 120 Surpass.

Ran it for the first time the other day in a Balsa USA 120 Stingray.Would not run for squat. Very touchy needle valve,poor acceleration, 16/8 prop 10% fuel with some castor thrown in. I know that many people in the past have had problems with this engine. I have misplaced all the t/s info that I put aside for the time that I would use the engine. Any one out there have any ideas, maybe putting a new carb on it,etc,etc. TIA.

Reply to
Ajn 521
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Your problems come from the pump putting out too much pressure. Don'ttry to adjust the pump, you'll have worse problems. The solution was arrived at by a showteam member of the Michigan Skymasters.The showteam used 3 Sig 1/4 scale clipped wing Cubs all powered by thethen new OS 120 pumped engines with C12 carbs. The settings were socritical on the carbs that a solution was needed to keep all 3 planes flying through the routine.The following was found to offer the best engine operation.Three outlet lines are needed on the fuel tank, one to the pump, thevent(and no muffler pressure), and excess fuel return. A tee isneeded in the line from the pump to the carb, as close to the carbinlet as possible, another tee in the fuel excess line, and both teesconnected together. This bleeds off the excess fuel pressure and willallow you to make a better carb setting. This info had worked it's wayto Clarence Lee, the RCM engine expert, and he has had it publishedin his RCM engine column with his endorsement. If you do a "Google"search, you'll probably find a few references in the newsgroup fromearlier queries.I've also heard of one modeler who put a plug in the carb line with a1/32nd hole clearance for fuel, but have no idea of how well theengine ran after that.I've followed this info on my own old(brand new, never run) 1.20 and with very minor adjustments, it performed fantastically. On a GP Super Skybolt,going straight up, you have to cut back on the throttle to keep it in sight.Good luck on yours,Harry

"Ajn 521" wrote in message news: snipped-for-privacy@mb-m17.aol.com...

Reply to
HarryK01

My 1st thought is that the fuel lines are hooked up incorrectly. The second is that you are not using an OS 'F' type plug. I have one of these motors and it has always run beautifully. A little rich at the low end but never quits. Do you have the book for it? If not, E-mail me and I will send you a copy via E-Mail. Gord Schindler MAAC6694

Reply to
Gord Schindler

Hi,

You must have the original version of the pumped 120. I bought one of the first sold locally years ago. The new version carb and manifold will not fit. Yeah, a real pain. This is one of those situations where OS didn't do enough field testing before marketing the engine. - just like the first versions of the 2C 91FX.

Follow the directions for using the "T" fittings in Harry's post. It was the only way I could bet mine to run well. Also, I found that using an on-board glow driver and an OS "F" plug would would keep the fire lit on down-lines when you chop the throttle. The thing has a lot of power once you get it running.

J

Reply to
Flightdeck

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