All of a sudden my 140L wil not start, never had that problem before! When I cracked the vent line to the tank there was no pressure in it, before, I always had pressure that would stay in the system a long time after running. If I disconect the lines from the engine and pressurize the tank and lines the pressure stays OK, there is no leaks. Is it possible the engine pump has failed? How can I check it out?

Maybe a hole in the diaphragm, but first make sure that the check valve hasn't tried to screw itself apart.

I checked the check valve Dave, I can blow through it one way and not the other. Is the diaphram you are talking about no. 48 on the parts list? Looks like I would just have to disassemble the regulator to replace it, are there any particular problems if I would try to do that at home?

Easy to do, just get the diaphragm, part No. YS 0730. While you have the regulator apart, change the plunger and spring as well. Then you start fresh. Make sure you mark the front of the reg so it goes back the same as it came off.

OK Dave, guess I should get a new gasket also. What address should I use to order the parts?

You can get them from Central Hobbies, or Call YS parts sometime this week at 775-782-4562.

Dave, I took the regulater apart and cannot see a hole in the diaphram, is there a way I can check it? There were little black specs inside after I took out the adjusting screw.
Tried to call YS Parts but their phone just rings busy, are they closed this week?

The black stuff can't be good. Could be an indication of something inside the engine coming apart if it's on the engine side. If you can't see a tear or hole in the diaphragm, it is probably OK.

Service should be there all this week, keep trying.

Not sure which side is the "engine side", is it up where the diaphram is? The black specs were down in the chamber the regulater adjusting screw, screws into, some were in the threads, after I took the screw out.

I'm out of ideas, maybe it needs to come see us.

I am going to give it one more try Dave, I seem to have pressure now that I have cleaned up the reg and re-installed it. The engine seems to have a lot more compression now??? After I spin it over several times and crack the vent line I get a hissss.

Hope it works!

Success Dave, after cleaning the reg it runs!!! With the Cool Power 30% heli fuel I get a steady 8500 rpm with an 18x6 Top Flight prop, tried an 18x6-10 Zinger but could only get 7100 and not reliable. Good reliable idle at 2200. The transition is smooth up and down the throttle but I get a lot of smoke going up from idle, I have not touched the regulater screw. Do you think it might still be a little too rich at idle?

Maybe too rich on the regulator try going in 1/4 turn see what happens.

Glad you found the problem.

The reg adjustment must have been pretty close to right, when I went in the 1/4 turn and increased the throttle the engine popped and stopped, everything went way lean. I ended up with it very close to the original position where I put it back together (flush with the reg casting). I got rid of a lot of the smoke, it idles at about 1900 and if I leave it there for a long time I still get smoke when I increase throttle but I am happy with it, wrung it out real good, top end is about 8600rpm and it sounds great, hope to fly it this weekend.

Terrific, but I would idle it a little faster, about 23 to 2500.

Good Luck!