Ryobi 31cc Starves When Inverted
04-11-2003, 06:50 PM
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Ryobi 31cc Starves When Inverted
Just finished a 4-Star 120 for my brother. Maidened it yesterday. Two deadsticks!
12 oz tank, 3 lines (one vent, one filler line with clunk and fuel line with clunk), primer bulb line is closed off with a piece of tubing and a machine screw. 87 Octane with petroluem oil at 40:1, original Walbro carb, with JAG conversion and carb spacer. 16x8 MA prop, original flywheel and magneto. Frank Bowman ring. Bisson Muffler.
Starts easily with minimal choking. Idles OK at 23-2400, reasonable transition to 7100 peak. I richened the topend to run at around 6900-7000 on the ground.
After about 5-7 minutes in the air, starts to sputter with high-G and vertical manoeuvres, and will quit when inverted, at high or low throttle settings. The first time it happened I thought I had the low end needle too lean, so I richened it up, had a great initial second flight, and then a sudden deadstick after about 5 seconds inverted.
Checked the clunks and both are free in the tank. It sounds to me like the carb pump ain't working so well. Any suggestions?
KD
12 oz tank, 3 lines (one vent, one filler line with clunk and fuel line with clunk), primer bulb line is closed off with a piece of tubing and a machine screw. 87 Octane with petroluem oil at 40:1, original Walbro carb, with JAG conversion and carb spacer. 16x8 MA prop, original flywheel and magneto. Frank Bowman ring. Bisson Muffler.
Starts easily with minimal choking. Idles OK at 23-2400, reasonable transition to 7100 peak. I richened the topend to run at around 6900-7000 on the ground.
After about 5-7 minutes in the air, starts to sputter with high-G and vertical manoeuvres, and will quit when inverted, at high or low throttle settings. The first time it happened I thought I had the low end needle too lean, so I richened it up, had a great initial second flight, and then a sudden deadstick after about 5 seconds inverted.
Checked the clunks and both are free in the tank. It sounds to me like the carb pump ain't working so well. Any suggestions?
KD
04-11-2003, 08:57 PM
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Ryobi 31cc Starves When Inverted
Does it fly inverted OK on a full tank? How long does it take to quit when inverted -- instantly, or can you fly it a while?
I'd think that the tank elevation with respect to the carb isn't much different inverted vs. upright, so I doubt it's the pump.
Grab some helpers and stick the nose straight up in the air and run it up with a 1/4 full tank. This will tell you if you have a pump problem.
You're sure your clunk makes it to the bottom (top) of the tank OK when inverted, and that the vent line is freely open??? I wonder if your clunks are interfering with each other. I assume you have the clunk on the fill line so you can drain the tank?
I'd think that the tank elevation with respect to the carb isn't much different inverted vs. upright, so I doubt it's the pump.
Grab some helpers and stick the nose straight up in the air and run it up with a 1/4 full tank. This will tell you if you have a pump problem.
You're sure your clunk makes it to the bottom (top) of the tank OK when inverted, and that the vent line is freely open??? I wonder if your clunks are interfering with each other. I assume you have the clunk on the fill line so you can drain the tank?
