I just put a DR, weak-ends pipe, weak-ends intake, and mikuni 20 on my 81 Honda Express (I guess it's technically an NA50 because I put the 2-speed motor on my 1-speed frame).
It runs *amazing* (and fast) with the choke on. Choke off and it sputters on initial acceleration (bogging) and then works great once it gets past 5mph.
So my brain says that that means I'm running lean -- it's getting too much air and not enough fuel. So I upjetted to 190. Seemed to work better. Then I tried running it with no air filter and it worked like a charm, choke off.
Logic tells me that means I need to downjet -- that it's not getting enough air. It also tells me the opposite -- that I need to upjet so that it gets more fuel.
As you can see, I have an interesting (and flawed) relationship with logic.
What do you think?