Ok, so I've been working on an 82 2 speed honda express nc50 I picked up at a yard sale a few weeks ago.
It had a carb on it, but the auto choke stuff was broken and missing, so I swapped it to a weak ends intake with a mikuni vm 20mm round slide carb in preparation of kitting it at some point soon. Also put the stockish boysen reeds in. Also has new battery.
Stock cdi ignition.
I'm using the 22 idle jet, and I currently have a 150 main in it now.
The issues I am having are:
No low end
Sputters and stumbles past 1/2 throttle
Top speed is only 20
Seems to run slightly better with even bigger main jet, or with the choke on, making me think it's lean
I have a clean tank, new fuel filter, new trans oil, new plug, air filter, etc...
Compression is 120psi cold
No air leaks - checked with starting fluid and found nothing
Plug shows black build up, showing me it's running rich, despite previous info on how pulling choke helps
Good spark at idle
Exhaust is still stock for now, but not restricted, does not run any better with pipe disconnected
I'm at a total loss on this. Any ideas?