My pal has a YS91 and he stripped the engine and did a rebuild properly. We tried to run the engine today and had some problems. The engine is turning an APC 14x10 and runs on Cool Power. We set the high end up and then moved to the low and mid. The engine will run fine with the throttle wide open and it will idle but when you throttle between 20% to 60% there is almost no response, only response we noted was the engine wants to die ... its like an electric engine running out of juice. There is no gurgling ...

If you push the throttle fast then when you hit 60% or more the engine will pick up again ... no sputtering at all. Its like running an electric motor. We tried to richen and lean up the regulator to no avail.

We need help!!! SOS!!! THANKS!!!

Did you put the regulator housing on correctly? The bump on the casting goes forward.

Dave ... will get my pal to check on that ... thanks.

I guess you're talking about me, tIANchi!

Yup, this ones got me stumped. Even got to the point where I couldn't stop the engine until I closed the fuel line with pliers. Wierd. But absolutely no midrange at all. I've been researching here for a week, which is why I didn't post myself, didn't want to bother ya'll with yet another "YS tuning problems" post.

I've been through it again today. I drew a schematic of the regulator and fuel system to see exactly how it works, then I physically checked the various functions, all is well. Tank held pressure for 24 hours. Carby is clean. 'O' rings, seals and gaskets all hold pressure. And yes Dave, regulator body was the right way around. Fuel is Cool Power 25% heli fuel with 20% oil.

For the next attempt I've set the regulator screw flush with the housing, the low speed needle flush at 2 3/4 turns, high speed at 1 1/2 turns. I've set the throttle barrel stop screw so the butterfly is just where it closes completely. Did I miss anything? Let's see if I can get this sucker to play ball.

I'll try to be a good boy and post back when there's something to say.

Cheers from the Barfly.