ORIGINAL: ZX1Ninja
I am either missing, not understanding, or just plain don't know something here. I have three different engines on three different planes that will not accelerate past half throttle.
O.S. 40 FP with 10x7 in raider 2
Tower Hobbies Pro 46 with 10x7 in another raider 2
Magnum 61XL with 11x8 in P-51 Mustang 60''
They all seem to be running good (best as I have been tought or learned), slightly rich with pinch test and light smoke trail. All running recommended recomended props, (or as close to as I can get right now) and 15% fuel. All throttle linkages set correctly and have free operation. Best I can figure is load / RPM (incorrect Prop??) issue, but I don't know because diffent props don't seem to help. Could someone please enlighten me as to what I am missing here and put me on the right track to resolving the problem. Or if the only problem is me.
There should be no problem with a 10-7 on the TT Pro .46, that combo is known to haul Quickie 500's at a pretty good clip. Should be fine on the .40 too, although I'd lean to a 10-6. Does not explain the problem.
You say the engines will not accelerate past half throttle, yet you say you do a pinch test. Help me out here - how can you be doing a pinch test at full throttle when they won't accelerate past half throttle...?
Step #1, open up the main needle 1/2 turn or so and start again. If they throttle up to a rich top end, I'd say you just discovered the problem. I agree with jeffie, my first impression is high speed needle too lean. The fact that all three engines do this is fairly strong evidence that you have a tendency to crank main needles in too far. It would be strange if all three had the same plumbing problem for example.
If you are having trouble still, then describe:
- behavior at idle if you pinch test, meaning warm the engine, establish idle, clamp the fuel line off tight right at the carb, and describe what it does
- what happens when you throttle up (don't slam the throttle, just move it from idle to full in a one second motion)
I pinch test at idle all the time, I find the standard advice "runs 2-3 seconds before it leans and dies" to be a pretty good baseline for the low speed needle at least.