As my first foray into gas, I've got a Ryobi 31cc with a Walbro WT324 (28/32 venturi) on a Giant Super Sportster. The engine ran great on the bench last week, 6300 rpm with a Top Flite 18x6 and it transitioned nicely. Put it on the plane without touching anything and the first time to the field it would not draw gas to the carb, we could only get it to run by squirting a little gas into the carb and then it would only run a few seconds until that was gone. I then discovered that it would prime if I held my finger over the hole in the choke butterfly while I flipped the prop. Back to the field today and I was actually able to get it to start by hand flipping it if I left the choke half closed. But it would only run on the prime until we opened up the low speed needle, finally it would run! The problem is that it will not throttle up, it dies every time. We opened the high speed needle all the way but could never get it to transition, then we tried it with the choke half closed and that worked much better. With the choke wide open the engine seems to be getting way more air than it has fuel for, or not enough fuel for the amount of air. I don't think the carb is too big for the engine because it ran great on the bench. My friend thinks there may be some crud blocking the high speed passages somewhere and that's why it's not getting enough gas. Sounds reasonable to me and I'm going to pull the engine tonight and look at the carb but I'm not sure how to clean/check it. The only other difference between the bench and plane is that I now have a felt clunk in the tank and a longer run to the carb, about 10". I'm using 3/32" neoprene tubing. Sorry for the long winded explanation but with all that info, does anyone have any ideas why it's not running like it did on the bench?

Dan