The 120SR is a vibration monster.
I've read on the forum that the YS 120sr works best with 15% & 20% fuel. Is that still the case (not sure why it would change but I thought I'd draw on everyone's experience....)? I also read an earlier post and it sounded like I should start with 3 clicks out and go toward lean from there.
Make sure you never exceed 16,000 RPM; otherwise, bad things happen
The manual is here:
I run my YS 120SR-X on 22% nitro.
The manual says the 120SR is spec'ed to run on 15% to 30%.
I have not heard / read anything about it "works best" at 15% to 20%.
It would be cheaper to run 15% (or 22%) than 30%.
But, I ran my YS 120SR-X on 30% for 2 gal and added a shim (just in case).
I could see heat being a problem at 30%.
But I still run a colder plug, too. Just in case.
There are 3 needles on the 120SR engine
The manual says mid & HS should be 2.5 turns out (say as the 120SR-X and many of the 91).
Set the idle first.
And try to get the idle as lean as possible (1/16 of a turn and then close the throttle a little. Repeat until the engine starts to do the ring-ding-ding and surges. Then enrich the needle 1/16 of a turn and open the throttle a little).
The pinch test is a good indicator that the idle is too rich.
Set the highspeed next.
Sure, 3 turns is OK (NOT 3 CLICKS
I believe the manual says 2 turns.
But at 3 turns, you wont really be able to buildup any heat.
But, lean the HS needle no more than 2 clicks at a time.
And only adjust the HS needle after you run the engine under a heavy load for at least a 5-count. Then land and adjust.
Then adjust the mid needle.
The mid needle on the YS actually has an affect; whereas, the OS's mid needle didn't do too much.
The OS was more like a 2-needle carb and easier to get it "close enough".
After you get the idle and the HS set, then do a full power climb and then instantly transition to a hover.
Big puff of smoke = too rich. No smoke = too lean
Believe 1/2 of what you see and none of what you hear.
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