I have finished all the conversion, made nice adapter and all works fine but...and here I need some help from somone who knows Walbro.

The engine runs great on idle and the Lo needle works fine. But when I get more than 1/4 throttle now the engine goes lean and dies. Turning Hi needle doesn't change a thing. Fuel pump works well. So I tried something else: I attached the silicone tubbng to the pressure mettering tube and I blew into it simulating increasing outside pressure. I was able to make such pressure (not much) so the engine was runnign well. The same effect was when I put the end of this silicon tube to the exit from the muffler. Exhaust blowing from the muffler created enough pressure in the tune for engine tu run smooth through entire throttle range.


So there is something wrong in the fuel mettering. The valve doesn't open. Is there some special passage that creates vacum on the gasoline side of the membrane to open the valve but in my carb this passage is blocked? Or should I simple play with the sping or the the lever? I know something is wrong on that side even everything visually os OK, so how to fix that?

The Walbro number is WT-308-1