The pinch test is a very good measure of how the plane will fly for the "non-racing" crowd.

You need to couple this with nose up and nose down tests at high, middle and low throttle.

Basically adjust the high end needle until the engine runs at full throttle w/o cutting out while level on the ground with some smoke coming out of the muffler.

PINCH the fuel line and release.

If the engine speeds up immediately, lean it out a bit and try again.

Do this until the engine no longer speeds up when you pinch it, at full throttle, then back off about 3-4 clicks, making it a bit richer.

Now take the trottle down to idle.

Let the engine sit for 3 minutes.

During this time the RPM's should remain steady.

If the engine starts out fast, but slows down over time, it is too rich on the low end.

If the engine dies when you throttle down, it is too lean.

If it remains somewhat constant in speed, then pinch the tube going to the carb, and see how it reacts.

This time keep it pinched until the engine shuts off, but note how the engine reacts.

If it, sped up GREATLY then died after a few or many seconds, it is too rich.

If it sped up a little then died, it is probably OK.

If it slowed down almost immediately then died it is too lean.

Adjust the low end needle until the engine will maintain constant RPM's at idle.


Once you have this set, run the engine back up to full throttle and point the nose up about 45 degrees and hold it.

The engine should speed up somewhat but not die. Hold this for 30 seconds.

Then bring the nose 45 degrees down and hold for 30 seconds. The engine SHOULD slow down, but it should not die out.

If it dies nose up, it is too lean on the high end.

If it dies nose down, it is too rich on the high end.

Adjust until neither position results in the engine dying out.

Now take it back down to HIGH idle or about 20-25% throttle and do the same test.

As before if it dies nose up, it is too lean on the low end ( low speed needle ).

If it dies nose down, it is too rich on the low end ( low speed needle ).

Rinse, lather and repeat.

You are best off doing the tuning and nose up tests with about 1/2 to 1/3 of a tank of fuel.

You should have a bit more fuel in the tank for the nose down tests however.