First off it's a project. I got it running but it won't rev up. It idles fine all day long. I would touch the gas barely or adjust the idle and it would kill it. I fiddled with the choke and it kicked up to a higher rpm and stuck there but I could rev it somewhat but it cuts out around half to three quarters throttle. Sometimes it will rev up but it cuts out, sounds and feels like it's starving for fuel. I have no filter or air box but it's running rich. Any ideas, feels like a plugged carb or fuel/jet issue but it did the same thing with the old carb. Plug is really black.

 

 

Checked the valve clearance? Manual shows 0.03mm-0.08 mm(.001-.003) intake, 0.05 mm-0.10mm(.002-.004) exhaust. That may have something to do with it. Here's free service manual if you works for you.https://www.google.com/url?sa=t&rct=...ECzxb-MN5X8laH