Honda Express NC50 Carburetor

Honda Express After-market Carb diagram

Honda Express NC50 Carburetor diagram

I have several Honda NC50 replacement carburetors in stock – buy now at $47.95. These are not original stock carburetors for the Honda Express but they might as well be. They’ve worked great on several different Expresses. Compare with buying a used Express carburetor on eBay for $175!?!

This carburetor bolts directly on to your stock Honda Express intake. The key measurement is 38mm from center of bolt hole to center of bolt hole on the intake. In the top picture, I have it working on a 1981 NC50 (auto choke). In the bottom picture, I have it working on a 1980 NC50 (manual choke). It will work on manual and auto choke Honda Express bikes. If you have an auto choke then you will just need to remove the auto choke hoses/lines and cap off the auto choke connections. If you have a manual choke carburetor, then you will no longer need the manual choke lever on the handlebars as this carburetor has a lever choke on the side. You may be able to connect your current choke cable to the carburetor but I have never tried.

Your stock air filter/box is slightly too small for this carburetor although you may be able to get it to stretch the extra 3mm (28mm). Otherwise, you can purchase a 28mm air filter for this. I recommend the K&N RC-2540 filter. It fits perfectly and it’s slim connections don’t affect the lever choke on the carb.

If your oil injector lines connect to the base of the intake then you can keep your oil injection system. If your oil injector line connect to the carburetor, then you would have to change out your intake to keep your oil injection system as this carburetor does not have an oil inlet. I just premix my fuel/oil at around 40:1 or 50:1. Or you can try to get really crafty and run a fuel T or Y between the oil injector line and the fuel line but that may affect your ratio. I would just premix and be done with it.

You will notice that starting greatly improves with this carburetor when compared with the old carb. Honda does not make the original stock carb anymore so you cannot get a new stock carb. Chances are your old carb is beyond cleaning/repair after 30+ years of gunk/dirt have accumulated inside it. Acceleration and top speed are pretty much the same after installing this carb. In fact, top speed may be 1-2 mph faster.

You will also be able to run a longer fuel line between the petcock and the carb which, in turn, will permit you to easily add a fuel filter between the tank and carb. A fuel filter is a necessity especially given the age of the fuel tanks on these bikes. Add a paper element filter to help eliminate rust from getting into the carb and engine from the gas tank.

I did not have to adjust my throttle cable at all when I installed this. It worked perfectly with this carb’s slide.

I ship these out via priority mail so you get it quickly and can enjoy your new ride!

Honda made several models of the “Express”. This carb only works on the NC50 and NA50. It does not work on the NU50 (urban express) nor does it work on the NX50 (Express SR).

Here I explain what I’ve pointed out in the carburetor diagram above. You can open this in a new window or magnify it to see it more clearly. I’ve just tried to explain some things about this carb so you can see how I made it work.

Starting at top left and working my way down and to the right:

1 – I used shorter bolts than the original ones on this carburetor to attach to the air intake and I didn’t use the stock air filter frame.

2 – I set the throttle stop screw about 3 1/4 to 3 1/2 turns out. After the bike fully warms up, you want to adjust this to where the rear wheel spins very slowly when the bike is on the center stand.

3 – I adjust the idle jet size so that I can turn this out about 1 1/2 turns. If you have trouble with cold starts, adjust this screw by turning it to the right about 1/4 turn at a time. Turning to the right richens the air/fuel mixture. Turning to the left leans it out.

4 – It’s a bit tricky at first but you eventually figure out how to hold the choke lever up and kick start the bike at the same time. After it starts, hold it up for several seconds and then gradually let it down. You may want to hold it at the mid-choke position as you work your way down.

5 – I left the oil injector installed but capped off its inlet and outlet. On other bikes, I’ve replaced the injector with an expansion plug. You will have to run premix with this carburetor; however, if your oil injector line attaches to the bottom of your intake, you can keep the oil injection system with this carburetor.

6 – You need a 28/29mm air filter for this carburetor. Another trick is that the choke lever can get in the way of the air filter so you have to find one that will allow clearance for the lever. I used the K&N RC 2540 here and am exploring other options. If your bike runs too rich and four strokes at full throttle too much, you can install a less restrictive filter or change the main jet to a smaller one.

7 – I did not have to adjust the length of the throttle cable which was sweet! I did remove the cable that controls the oil injector. Hopefully, you don’t require throttle cable adjustments either.


Carb installed on a 1980 NC50.

Carb installation video on 1980 Honda Express NC50 with manual choke.