I have a new(unused) but 6 year old OS 40LA that i installed in a goldberg tiger 2 ARF. after breaking in motor( the same way i have with previous engines) i put the plane in the air and after about 3 min it dies in mid air...so we start it up again and it runs fine so we put it up again and it dies agian...this time we run it on the ground and (fatten it a little) for about 10 min and it doesnt die so we put it up and it didnt die agian for 2 more flights (10-15 min each)...the next day me thinking it was going to work we go flying and it dies after about 2-3 min in midair...so we richen it up even more and go up again...it does good this time till i am flying it inverted for a while and it dies... i dont know what to think the klunk is moving freely i am using omega 10% just like in other OS 40 LA's that i have but it just doesnt seem to want to run...i have the baffle taken out but that never made a differnce before. Does anyone know what the problem could be?

G'day Mate,
Check for pin holes in ALL your fuel lines, sounds like it could be in the tank, as the fuel level goes down, the pin hole is exposed & sucks in air, thus leaning out the motor, also make sure that the clunk line has not come off inside the tank. Pull out the tank & check it, this happened to one of our guys last week, the motor would start but as soon as the nose of the plane was lifted, it stopped.
Good Flyin Mate,
Allan.

just checked and no pinholes and the klunk is still attached

I to had the same problem with a 25 la motor. We took the baffle out and the same thing happened that you are saying. We put baffle back in and the problem went away. We also have a 46 la thats doing the same thing but we cant find the baffel we took out . Hope this helps as we tried everything to before putting baffel back in.

All my LA's do the same thing.Every 1/4 tank, I had to readjust the needle valve. I was running 10% nitro 16% oil. I went to 15% and it's not quite as bad. Once the fuel level gets below the carb, it has trouble maintaining enough pressure to push the fuel up to and through the needle valve. I have 2 .25 la's, 2 .40 LA's and a .46 LA, and every one of them do the exact same thing. Someone had suggested putting a check valve between the exhaust and the tank, but without a regulator and a pop off valve, I don't see how that would work. I even installed a larger pressure nipple, and the results didn't change. The only other thing I know to try is restricting the exhaust, but then you start hampering engine performance. All but 1 of my LA's is sitting on a shelf (next to my Super Tigre G75), and I have gone mostly to 4 strokes. I mostly put my 2 cycle OS' on a couple pieces of balsa or plastic that I'm glueing together so the wind doesn't blow it away.