I have a Fox 2.4. This engine has by far been the best starting gas engine at the field. The past three weeks its starting has been getting worse. five flips choked an pop, then four to fly. Was 3 choked ,1 to fly. It runs great till about three min into the flight, Then the power just starts fadeing off. First it starts at wot then with the stick at wot the rpms slowly fall. Bring the stick to half an it runs ok there for a few seconds then it starts fadeing off there aswell till it finally deadsticks.

I bought a new carb kit for the walbro. Found the pump diapram was wrinkled an the lil round screen had tons of junk in it. Replaced the screen an diaphram, Thinking my problems were solved.......

Next day at the field the older guy at the field(when he talks everyone listensVery repected) told me to tie it down to re-tune it. So we did. Peaked at 7550, richened it to 7300.

Taxied it around for a few mins to see if it would die an it ran great..........

Took off an noticed in straight level flight that engine would speeds up on its own an fall off with out any throttle...........Maybe 800 to 1000 rpms not sure though. Does not do it on the ground.

I have changed oil mixes from air cooled at 40:1 to amsoil saber at 50:1. Is there anyway this oil change could be causeing this problem? If not what might this be?

Many thanks in advance.................

Even though you richened the top end make sure that it is not running lean and overheating, as engines set lean can be a bear to start. Otherwise it sounds like it could be an ignition related problem, as maybe the battery is not holding up or the ignition itself is acting up.

Karol

I will look into that. Would the ignition make the rpms jump around if it were going bad? It is a C&H.
I have a 2000 ma Ni-mh batt. think it might not have the ma needed for the job?

A fully charged 2000 mA battery should be more than enough for your ignition for a full days flying and then some. Interference from the ignition system can make the rpm jump around all on it's own and so can the carb in a cowled situation. Is the engine cowled and if so have you tried flying it without the cowl to see how it behaves in the air. Considering that all seems to have been working well and just got worst over time there are a few other things you can check or do such as, change the plug, check that the plug cap is on real tight or that the ignition sensor mounting is not loose.

Karol

Thats a good idea. I have a new cj7. The plug in it looks good an sparks fine out of the engine. But I have seen plugs not do a thing once put in the engine...............I have flown it with no cowl an it still acted up. Halls magnet seems to be good an tight. I will try a new plug in the morning if its not raining

What brand is the CJ-7 plug, hope it's not one of the current cheapies. It's a good practice to use one of the more popular brands like NGK, Champion or Denso. The fact that your engine only acts up in the air and has become difficult to start really leads me to think that it could be your mixture that needs some adjusting. Try running a bit richer just for a test and see what happens.

Karol

"the little round screen had tons of stuff in it" Is the pickup line in the tank falling apart ?

Or, make sure that you are using a gas compatible tank stopper cause if you are not that could be what's sending all that junk to the carb screen. Make sure it's not one of the so called gas compatible black coloured stopper as those are known to fail after awhile when in contact with gas. Use the Dubro brown coloured gas stopper which is known to work.

Karol