Hey gas engine experts. I have a puzzling delimma. On an RCS 180 that has been running great since around 1999 I have started having problems.

It started when I tried to fuel it and fuel began gushing out of the carb. Took the carb apart and cleaned it like I have done in the past. This took care of the the fouled fuel metering valve so I could now fuel it without fuel running out of the carb. Started it and it idled beautifully adjusted the needles and it performed flawlessly. I then filled it up to fly again and I couldn't get it to go past idle,,, like nothing was drawing off the high speed needle. Advance the throttle and it dies like its lean. If I bring the throttle back when it starts to lean out it idles like a champ. It will idle the tank dry.

So I ordered a carb rebuild kit and installed it. Replaced the metering pin, lever, gaskets, and diaphrams. Blew out all the ports with compressed air and carb cleaner. Cleaned the pulse opening to ensure there is no blockage. I reinstalled the engine in the plane and no change. Can't get it to go above idle. This is not a reed engine it is a disc valve engine. Also, I pulled the head off to see if there was some blow by on the rings,,, All looked good.


Your advice on what to do next would be greatly appreciated


Thanks in advance,

Robert

Did you install the gaskets and diaphragms in proper order?

On the jet/bowl side, the fat gasket goes on first and the thin gasket with the metal disk in the center goes on last.

On the pump side, the this gasket with the flappers in the center goes on first. Thick gasket goes on last.

Yup just checked them. They are in right. It almost acts like there is no high end jet. Is there some way to pull out this jet. I think they are pressed in.

Robert

Probably got some dirt or shelac into the high speed needle port. If the highspeed needle isn't adjustable get a new carb with adjustable needles. An adjustable needle can sometimes be run in to crush an obstruction and clear it.
Your local saw shop/repair guy's will have a box or two of old usable carbs. If they don't give them to you, they'll probably only charge about $10 for one that works.

PROBLEM SOLVED!!!

I disassembled the carb again and blew it all out after letting some carb cleaner soak into all the ports. This time I also blew into the high side from inside the venturi. I can only assume that the high side had something (probably shellac or bits of rubber from all the old parts) gumming it up. On another note this engine performs pretty well for its age. Never been rebuilt just seems to keep on chugging. Transition is smooth, idle is low, and it bangs a 20x8 Mejzlic pretty darn good. Pulls a Cermark Pitts straight vertical ~11lbs.

I should probably not let it go for 9 years before rebuilding the carb.

Thanks again guys for your prompt response.

Robert

I'd take the high speed needle out and blow air through the passages backwards.

CR

Good job!! [sm=thumbs_up.gif]

Now post a pic of that bugger in the plane. [8D]

Charley, that is what he did, and indeed it solved his problem.

Well, I had already cowled it by the time I read your message. But here's a pic of it hanging in the garage ready for Sunday fly-day.

Nice looking models you have there. Looks like red and white are your favourite colours too

Karol

Karol,

Thanks. The red and white just seemed to work out that way. With the Pitts this is a scale color scheme and the only color Cermark was delivering back then (there are many flights on this bird). As for the Flanker its kinda hard to do a Russian jet in much of anything else. Sure there's the military colors and the Swifts aerobatic team colors but I really wanted it to stand out since it moves out pretty good.

Robert