Saito FA-56 Stall When Snap Rolled

by Matt Colbert
(Sebastian, FL)

I have a Saito FA-56 in a Four Star Forty with Sullivan 6 oz tank (That is the tank that came with the kit). I have flown this plane over 200 times without changing anything. It now stalls EVERY time it is snap rolled.

The high end is set to run rich. The low end is adjusted and makes a smooth transition to full power. I get good smoke when flying level. Roll it and it stalls. It NEVER did it before. Have also tried to run it a bit extra rich. No change.

I have:

-Replaced the glow plug with new OS F-Type TWICE

-Replaced the fuel tank plug, brass lines and the fuel lines (Used the original tank) The clunk is NOT hanging up on the back of the tank.
Replaced the TANK, PLUG, BRASS, CLUNK, and ALL fuel lines AGAIN. No cuts or nicks in any of the lines. This tank is an exact replacement for the original that flew over 200 times. Don't think tank height is an issue. Checked clunk on the back of the tank again.

-Removed motor and carburetor. Cleaned all carburetor parts, needle valve and backflushed. No sign of dirt or grass in carb. No loose back plate or head screws. Reinstalled carburetor. Grommets for the carb tube going to and into the head all looked good.

-Removed muffler and disassembled. Muffler tube, nipple and baffle are all clean and open. The muffler generates plenty of backpressure. The crankcase vent nipple is also open.

-Removed valve covers. All pushrods in place. Gaps are .004 and .006.
You can hold it level, nose up, nose down, and inverted. It does not do it on the ground. The engine stalling is instantaneous when it is rolled.

Any ideas on what to do next?

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