ORIGINAL:
Whats the best way to know how much to lean the bottom end. Just look for a smooth transition? I was about to take 5mm off my header, but I'll try this first. The engine was good straight out of the box, so I want to mess with it as little as possible. Ran about 7700 rpm on the ground, which local wisdom say's is about perfect.
Steve,
I was reflecting with a fellow pattern flyer on the weekend that all planes that sustain minor damage in those early flights fly better in the long run! I have done the same myself on more than one occasion . . .
On the 140, I would try a couple of things on the transition -- one is to lean the low end a touch, a tenth of a turn max and see if it improves. There is no recipe, just try it and see if it gets better. It won't take much. The other is to decompress with a second head gasket. I am less sure on the later of these -- I did it to both of mine, but they are a couple of years old and I heard someone suggest it was no longer necessary (but since then I have contradictory advice). Any recent view out there? Most of the guys I fly with are flying 15% nitro and 17-20% oil (so if you are flying with 20% nitro you may want to lower it a fraction and see if that helps -- you will still have ample power unless you have a 6kg plus Cyclone!). 7,700 is in the sweet spot -- one of mine runs less than that, one slightly over, and I haven't worked out why!
And unless there is something very wrong, trust that idle!! They tick over at slow revs superbly, albeit a little roughly on a soft mount.
David