The engine is an OS 32. The trouble is I can't seem to keep it running. I replaced the fuel lines and the glow plug. I followed the manual on how to set the needle valve and the mixture screw. I've leaned it out and richened it up. Here is what it is doing.

I can get it started with out too much of a problem. When I open the throttle, it runs for anywhere from 1 to 5 minutes, and dies. Bring it back to the starter table and try again. It seems that the fuel is not getting into the carb, and I can't figure out what is causing this.

I apply the starter motor to try to start it. You can see the fuel in the line that leads to the carb. As the starter motor turns, you can see the fuel in the line advance to the carb, then it goes back to the tank. Open up the needle valve one turn and try again. Same thing. I had the valve open 6 turns and it did no good. The fuel would advance and go back to the tank. Can anyone tell me what causes this and what I can do to fix it?

This bird is grounded until I get this one figured out.....

sounds like you're not getting any backpressure into your fuel tank.....Is the line securly connected from the muffler to the pressure line of the tank? On some tanks, there will be 2 plastic nipples that are molded into the tank......only one of these will have an opening in it.....that's the one you need to use for your pressure line.

Mike

My guess is that either the tank is in a bad position relative to the venturi, or once it gets hot the engine is losing compression. How old is the engine and do you have any history on it?

Same problem happened to me. The problem was my tank, it wasnt holding pressure. The stopper for the tank just wasnt sealing right. My suggestion is to check that out and buy a new tank if necessary. Also, make sure the tank is level or sightly above the middle of the carb venturi.

The engine was new when I got it. However it is about 10 years old. Of course it sat for 9 years so it doesn't have alot of run time on it. I bought it, ran it for a season, and put it away as I got interested in other things. I guess the first stop is to remove the tank and see if that is where the problem is. I'll let you know. Thanks for the help.

I would change the O rings on the needle valve and the carb. body. Tank pressure has nothing to do with this problem but leaking air on the supply side could. Two cycle engines can run without any tank pressure and did for many years before muffler and pressure taps.

That's what made me think it wasn't an air leak of sorts

Sounds like maybe the tank vent is blocked. (?)

Well here goes. I checked the fuel lines and found one that was cracked. Make note to self. When replacing fuel lines, toss the old ones out. I replaced them with some lines I found in my field box. Guess they were used. Anyway, I pulled the engine and replaced the o-ring on the carb and the needle valve. Put it back together and tried it out less than an hour ago. Same damn thing happened. However, it only happens when the engine gets hot. When the engine is cold, it is fine. I am running the correct mixture as per the engine instructions. After it occurs, if I let it set to cool off, it is fine until it heats up again. So what ever is causing it, it is a heat related issue. I did notice in the grand scheme of things, the threads for the glow plug are hosed. Apparently, somewhere along the line, I cross threaded the plug in the engine. Could this be causing the problem?

Flip the plane upside down and try it. If the tank is mounted too low, then it will be too high and flood but it should run good until that happens.

The cross threading MIGHT be causing the problem.

Try changing the plug and while your at it, check if the clunk is stuck or fallen off.

As a last resort, you might want to send it back to the factory and tell them to put it back to factory specs.