I have a Ryobi 31 in a 4*120 and I got troubles. This is a brand new engine, and it's only turning about 6100RPM with a Zinger 16-10. I'm using 40:1 fuel and a C&H ignition. Battery is new. Brand new ignition. New plug. It's all new. Twin ring. No compression relief slots. Long shaft.

I switched out the stock Zama carb for a WT610 because the Walbro has a choke butterfly. The WT610 is the same size venturi as the opening in the backplate on the engine. It's about 15.5mm wide. It has a 34 stamped inside the carb throat. RCIGN1 told me how to read this number. It's measured in 64ths of an inch. So, 34 is read as 34/64.

I can get it started after a few flips on choke. It will idle and transition pretty decent, but it slows down and abruptly dies at about 1/2 throttle. I started with both needles 2 turns out. Richened the low speed so much that the engine started to slow down and load up a bit. Still won't go over 1/2 throttle. Richened the high speed--thinking that it was leaning out. No effect. It sounds to me like the engine is getting too much fuel and just drowning. I've richened the high speed to 4 turns out and it won't go over 1/2 throttle. Leaned the high speed down to where it won't even run.

Do I just have to much carb on it? I've had one of these engines before, and I put a carb on it that was the exact same size as the backplate opening, and the engine ran very well. I believe that was a WT438.

I can go back to a stock carb with a little bity 24/64 opening, but not getting much power out of it. One local guy who does a LOT of engine conversions told me that my engine is only turning 6000RPM on a 16-10 because it's brand new. Less than 1 gallon of fuel through it. Probably only about 5/8 gallon of fuel through it. He said it will break in over 5 or 6 gallons and pick up as much as 1000RPM. Do they really pick up that much when they finally break in? If so, then I'll stick the stock carb on it and just run it. But, it just seams low on power with the stock carb.

Is it possible that the WT610 is just too much carb for it, and I'm drowning it?

Thanks