I have an YS63 with about 2 gallons on it. I was running it with an Enya 3 plug and it did not have a good idle but midrange and highend as well as transistion were good. Today I went flying and my plug was dead so I changed it with a new OS F I had in my flying box. It has changed completely. Idle is very good and will idle for ever. The high end is also good and I can adjust it as lean or as rich as I want, but I have a problem in my midrange. It is doing a terrible sound that I think is detonation that disappears if I am able to go to full throtle. Adjusting the high end needle has no effect. It seams that the plug is hotter and needs to run richer. How can I adjust it to make the midrange richer?

The regulator screw controls transition. Open it 1/2 turn and see if it improves.

Dave

Controlling transition means making the midrange richer or leaner? What is the exact effect of turning the regulator screw?

The screw controls the the transition between low and high throttle. If the mid range is lean, obviously you would want to open the regulator screw by some amount. 1/2 turn will produce enough change that you can easily tell the difference. If it's too rich in the mid range, turn the screw in.

Don't be afraid to play with it, it is the heart of the YS engine.

Dave

It really makes a difference. I turned it 1/2 a turn and the midrange was way too rich. I have backed it up and with less than 1/4 of a turn I think it is right. It is doing a lot of smoke now in the midrange that did not do before. I hope that I have not damaged the engine from running it lean.

I forgot to give you the thanks Dave. Continue with your good work.

Thank you,

Joan

Glad to be of assistance, especially when I get it right!!!!!!
Let me know how it works out.

Good Flying,

Dave Shadel