Not sure of CC size of the gasser. Need to know what size prop to use. Gasser is mounted on a PT-19 82" wing

Thanks

A homelite 25 with the stock (20) carb uses a 16 X 10 and turns about 7000

We need to know the number on your carb? Or something about it anyway.

It looks like a Carr Precision muffler and a CH ignition conversion

A 25cc will have a divider in the exhaust port and a 30cc will not unless someone removed the divider from the Homelite 25.

Homelite 25 or 30 with a (28) carb will pull a 18 X 8 7000/7400

With stock porting, these engines seem to do best when propped in the 6800 to 7500 rpm range

It's a 30CC, I have the same engine and will have a "30" on the intake side by the right side cylinder bolt hole. Look and see.

It does have the divider in the exhaust port. The carb is a Walbro WA-167A. I have it running between 3000-7000 rpms.
I'm having a little trouble with transition of the throttle. Sounds good on the bench but stutters on take off and when you throttle down
in flight. Tries to go into 4-cycle mode.
Please go to my youtube link and you can listen for yourself. What carb adjustments would you recommend?
These videos are of my very first flights with a gasser.
Thanks

http://www.youtube.com/watch?v=PX685o4LQoU
http://www.youtube.com/watch?v=xC0QXAcbSSY
http://www.youtube.com/watch?v=L8C991s0kS8
http://www.youtube.com/watch?v=xnER8e8Nhvc

Actually it sounds like you are pretty close. The divider in the port definitely means it is a 25cc. I noticed during the one flight shot that it four stroked during a dive. That can happen with two stroke gas engines, especially if your prop load is a bit light in general, or if your pitch is a bit high on the prop. The engine is all set up and tuned with a static prop load. Then in a dive, especially if the pitch is a bit high on the prop, the engine "unloads", (is not working as hard) and the engine has too much fuel for the load and therefore four strokes.

Keep leaning the low needle in small increments until you lose good throttle transition. Then go back 1/16 to 1/8" turns richer.

But really, the flight sounded pretty good. Just a few burbles here and there, no big deal... Walbro says in their tech literature that an engine might need to be richer than optiminum at idle/midrange for good throttle transition. This will often make them ocassionally four stroke in flight. If it really bothers you, then keep leaning it on the low end, and learn to advance the throttle slowly. Remember to reset the high end each time you change the low end, as one affects the other.

AV8TOR

Another thought. Since you are new to gassers, you might not realize that they don't need to be set rich like glow engines. Tune for max rpms with a tach, and then richen the high needle about 1/16 to 1/8 turn, no more.

AV8TOR