what happened? what changed??

[GremlinX]

30% Extra and DA 50... New motor with 1.5 gallons. Tuned it and runs super. Flown everyday this week after work. One day great. Next day after storms came through,much cooler and dryer air... It was super rich and 4 cycling bad. On a nice cool dry dense air day... One should need to richen. What happened? Needles did not move in flight.

[TheTank]

Fuel Change? Maybe some not-so-desirable fuel in the last tank... got it tuned on that fuel and it was fine until you got some good fresh stuff. I have also noticed at they break in slightly, the mixture changes slightly/needs to be adjusted. Those are the only two things I can think of.

[GremlinX]

Same very fresh 2 gallons of fuel....

[Kiwi]

Gremlin.

Maybe a smidgen of junk is under the needle. Changes in air density etc dont normally have a huge impact on the engine. Its not like you tuned it at sea level and tried to fly it at 10,000 ft.

Kiwi

[jack01]

I'm going with Kiwi and saying it's some junk in the carb. Any time one of these engines does something unexpected, the carb is a good place to begin troubleshooting. You also might want to try a new spark plug if it still does it.

On another note, my 150 doesn't always play by the rules in regards to air temperature/density. I know that colder air normally is more dense, therefore the engine should run slightly leaner for a given mixture setting. However, my 150 seems to be more affected by the cooler air cooling the cylinders more than warmer air would. I'm talking about an 80 degree day, VS a 55-60 degree day. Once the engine warms up, it's back to normal. Does your 50 do this once it's warm?

[GremlinX]

Started and flew yet the 3rd day in a row... Just fine. It just suddenly needed leaned. Strange. Its all set now and has been.