ok i have a os ax 55 on my decathalon and i can keep it running on the ground but when i get in the air and fly for about a min or two it acts like it loses fuel and just dies... i have a pits muffler on it had to jb weld on of the pipes back on it it had bent and went to bend it back and it broke well the jb weld didnt hold and one of the pipes fell off of the muffler... do yall think that this might be causeing the muffler not to hold enought back pressure on the tank and making it lose fuel

It very well could be a back pressure issue. I'd also look for things like cracked fuel lines and make sure the engine isn't too lean and overheating in the air.

we thought we had it to lean but we richened it up and it still did it and then i thought i might have the plane over proped because i had a 13 x 4 on it and then i put a 12 x 6 on it and it did it again i am going to look the plane over good tomorrow night and see what is going on

I had the same issues with my 55 AX in Phoenix Decathlon . I put on a 12.25 X 3.75 APC and problem solved. do you have the cowl installed? The cowl openings in front also do not allow for proper cooling if the engine, I took some inch foam (wall insulation that you can get at home depot) and as you are looking at the front of the plane, blocked right side opening. This alllows the head of the engine to cool more efficiently. There's a link on the ARF forum that dicusses this issue in great detail. With the prop setup and foam, I have had no more deadsticks and the plane will hover. and has unlimited power!

BBrown,

what plug and fuel are you using?
Is your engine settings correct?

can you provide all this detail?

Simply saying I fly it and it dies is not very helpful. This interests me because I had a similar problem but on a GMS 2000 47 and after I retuned th motor after some "experts" in the club looked at it I found they had fiddled the low end too rich causing flooding which resulted in unburned oil turning to syrup in the engine.

After i flushed the motor out with carb cleaner (aerosol you can buy at motor spare outlets) and fiddles the settings its run reliably again.

i had an experianced tuner tune the motor the low end is just right we do believe

Make sure you have provided plenty of outlet area at the cowl bottom or you have turned the cowling into a stagnant bake oven and please plug one of those muffler outlet tubes, These notoriously destroy the fuel delivery performance on muffler pressure with many engines. With mufflers one size does not fit all regarding fuel delivery.

John

yeah what John said. THere is plenty of outlet area, at least on the phoenix. but too much air flowing over the exhaust side of the engine, mine 55 is mounted 45 degrees inverted. That is why I plugged the cowl inlet in front of the exhaust so that more air was directed over the head side of the engine.

here's the forum link that has a pic of the foam mod I did to the cowl, courtesy of Da Rock
http://www.rcuniverse.com/forum/m_49...tm.htm#4937320