140L is new this season. Dave, this is the one that quit shortly after take-off on its first flight in my QQ Yak in March that we talked about. You told me it "quit rich". Plane is rebuilt and the 140L has approx 1 gallon of 20/20 between 5 flights plus break in stand time before reinstallation. 18x6 APC, high end in the high 8k range, nearly 9k. OS-F plug. (2) Craptrap filters - on both supply and pressure lines. Regulator screw is set flush with casting. NMP QQ canister style muffler and header. J'tec iso engine mount.

High end is fine, tuned to approx 150 rpm off peak. Makes plenty of beastly power and flies the plane great. However, when sitting at low idle in the 2000-2400 range, it shakes a lot, as if trying to quit. Getting it toward 2800-3000 and it smooths out. Engine loads up with fuel if idling for 20-30 seconds, which is visible when throttling up. Gets rougher when ni-starter is removed. So, it sure sound like it's rich to me. I need to keep the low idle fairly low, or this plane keeps flying!

Airbleed - I started with the factory 1-1/2 turns out on the airbleed, and have leaned it out to 4+ turns out. I've not had a YS needing to be that far off factory settings unless there was a problem. At 4+ turns out, it's improved enough to be flyable, but still shakes and has some tendency to quit when taxi-ing. Tank pressure is excellent, and retains the pressure overnight, so check valve is working.

I pulled the regulator apart, to make sure there was no debris inside. Plunger, poppet valve/spring, diaphragm, passageways all clean and clear. It ran/flew the same afterwards.

Transition is a bit slower than I'm used to on my other YS engines, and idle is rich/rough. Perhaps the regulator just needs to be screwed in a bit?

Thanks, Dave.

I'm surprised you haven't set the regulator leaner. Why not?

Reset the idle screw to about 2 turns open and play with the reg, you can't hurt anything.

Dave,

In the hot sun, my brain must have been baked. I thought about the regulator setting on the way home. Once upon a time, I recall you telling me that the regulator primarily controlled the midrange and transition by regulating the max fuel available under transition. I guess I didn't consider that it would have much affect on the idle. Makes some sense that it would.

Will post back my results.

It has more of an effect when the idle is up over 2000 rpm. I like to see it at 2200 to 2400 so the regulator is in play at that point.

Let me know how it comes out, OK?

Dave, will do. Probably next Saturday. Note: I was intentionally running my low idle at 1900-2000 so I'd hopefully be "off the pump". My high idle was 2800 or so but it was fairly smooth.

Let me know.

Dave, I was able to improve the idle acceptably today by "leaning" the regulator.

1. Turned the regulator in, approx 1-1/4 turns leaned in from the stock position.
2. Airbleed screw was turned in (from the 5-1/2 out!) to the stock 1-1/2 position, which worked better than 2 turns out.
3. Obviously I also re-did the main needle and then re-set the idle. Getting 8900-9000 peak on the 18x6 APC. set at 8800 for flying.

Lo idle is 1900-2000 and high idle is 2500-2600. Lo idle lopes, and sounds like tick.tick.tick.tick.BAM! tick.tick.tick.tick.BAM! but it does not try to quit any more. It's solid, just not buttery smooth until I move it up to high idle, which is very smooth. Transition from low idle is solid and quick, without the big blast of smoke I had previously. At low idle, the 140L is transmitting the power pulses into the airframe which is magnifying them, so it sounds louder and rougher than it really is, but it's acceptable. I'm usually at high idle, except for landing.

I never try to idle them that slow for the reason your have mentioned. Bump it up to 2200/2300 and see if it's more acceptable. Going to 30% heli fuel will help too.. Try it sometime.