Kitted Honda Express Carb/Jetting/Air Filter Question

Jason Evans Groth /

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?

Re: Kitted Honda Express Carb/Jetting/Air Filter Question

What was your jetting before 190? "Bogging" can occur with a jet that is too big. I have a 145 main jet with almost the exact same setup on my NC50. I'm thinking it's almost too big for my dr kit....maybe. I need to play around with it. It might also be your idle jet. What size are you running?

I recently had this kind of problem on my MB5. Bogged under 5mph, but pulled away after that. I down jetted and that helped my problem. I may need to even more.

Hope some of this helps. Good luck.

Re: Kitted Honda Express Carb/Jetting/Air Filter Question

Jason Evans Groth /

Thanks, Daniel. I am running the stock idle jet right now (the size of which I can't remember). In the past most of my problems have been solved by down-jetting, but this case seemed weird to me since it worked so well with the choke on.

I'm also breaking this guy in right now and didn't want to run it too lean. But I'll throw a smaller jet in (maybe go down to a 170) and see what the results are.

Frankly, I think my Puch probably needs to be downjetted, too... so it looks like gas-hands for me tonight when I open up those Mikunis. Thanks so much for your advice!


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