ClausBN

Ive seen a videos of a Saito FG 57 boxer and my own FG84R3 do this when the plane does a roll. Why does it do it and whats the cure ?
https://www.youtube.com/watch?v=kHmzFtTLenE

w8ye

My Feedback: (16)

The mixture changes during the roll

ClausBN

Thx - kind of obvious ;-) I was hoping for some details.

w8ye

My Feedback: (16)

The design of the carburetor does not have a very strong pump and the regulator fails to maintain constant fuel feed to the engine in all positions.

The CH guy has used a different carburetor to get around this problem.

ClausBN

Who is the CH guy?

w8ye

My Feedback: (16)

Adrian

https://www.ch-ignitions.com/

ForcesR

My FG-36 also coughed during rolls before and after being fully broken in. I suspected that the engine was still running a tad rich resulting in the cough during aileron rolls. It no longer coughs during rolls and has flown cough free for numerous flights since I identified the problem with my engine. The engine had good transition from idle to full throttle, so I began to experiment after each flight. I began with HS needle adjustment, I leaned the HS needle 1 minute at a time after each flight to see if the cough would disappear. I leaned the HS needle a total of 5 minutes and stopped due to the possibility of leaning the engine to where it would overheat and stop in flight. I returned the HS needle to where I had it originally set before the 5 one minute adjustments.

I then began leaning the LS needle 1 minute at a time after each flight. When I reached the 4th one minute adjustment and launched the Spitfire to confirm if the cough was still there or gone, surprise, surprise, the cough had completely disappeared. Yahoo the FG-36 became cough free during aileron rolls since then! Also the engine picked up an extra 200rpm at full throttle, it now tachs at 7700rpm.

ClausBN

Thanks. Thats a great approach to solving it.
By "one minute" you mean 1/60 turn on the needle or how much did you lean it each time?

ForcesR

Yes that is correct, 1/60 turn equals 1 minute, just like the movement of the minute hand on a clock. I leaned the LS needle 1 minute at a time between test flights until the cough disappeared at the 4th minute adjustment.