1980 honda NC50 questions

Joined: January 5th, 2008, 11:12 pm

January 6th, 2008, 3:15 am #1

I am near giving up on getting my 1980 honda express nc50 to run. I can get it started by manually choking the intake on the carb with my hand, it will run with the choke out and in, but if i open the throttle, it will run fast and then die like it is starving for fuel. Also when it starts, it runs really fast. Any ideas? It sat over the winter a couple of winters ago, so i have cleaned the petcock and carb. Is there a source for the Keihin carbs or any aftermarket alternatives. What size is this carb? Keihin makes i think 28 mm carbs, but I am not sure how they would fit this applivation. The headlight also just blew out. I have the battery hooked up, but did not check to see that the fuse is still good. I know that running it without the battery blows the headlight, but if the fuse is good, what is the name of the thing that i replaced one time? I think it was the rectifier. Thanks for your help.
Quote
Like
Share

Joined: October 18th, 2003, 2:45 pm

January 10th, 2008, 7:08 pm #2

There is a passage after you remove the float bowl that gets missed almost every time someone attempts to clean the carb.It's underneath and hard to find.
But you might have a cap not venting like in the lower post where i told him to clean petcock and make sure the cap is venting.
Also replace a spark plug at the first sign of trouble.
If you have an air inleakage,you can find that by spraying carb cleaner at connections of carb to intake,intake to engine,or cylinder base to block.Do this when the engine isn't too hot,and notice for any roughness or rpm changes down or up.
Your carb is WAY smaller than a 28mm,so don't try that. don-ohio
Quote
Like
Share

Steve
Steve

May 1st, 2009, 9:17 pm #3

I am near giving up on getting my 1980 honda express nc50 to run. I can get it started by manually choking the intake on the carb with my hand, it will run with the choke out and in, but if i open the throttle, it will run fast and then die like it is starving for fuel. Also when it starts, it runs really fast. Any ideas? It sat over the winter a couple of winters ago, so i have cleaned the petcock and carb. Is there a source for the Keihin carbs or any aftermarket alternatives. What size is this carb? Keihin makes i think 28 mm carbs, but I am not sure how they would fit this applivation. The headlight also just blew out. I have the battery hooked up, but did not check to see that the fuse is still good. I know that running it without the battery blows the headlight, but if the fuse is good, what is the name of the thing that i replaced one time? I think it was the rectifier. Thanks for your help.
the nc50 carb as far as i can measure with a ruler is 17mm. I am considering upgrading to a 20mm although they all have 48mm bolt patterns that ive seen whereas the nc50's pattern is 38mm. these carbs are meant to be a bolt on upgrade for the xr/crf50's. there are many on ebay that go for around 40 dollars shipped. i or you should be able to modify either the carb bolt holes or the manifold bolt holes to nicely "rig" this carb to fit. also the intake hole should be enlarged to 20mm.

there are also similarly priced 18mm carbs on ebay, but they also have the 48mm mounting bolt pattern.

as far as your carb, i also feel like you may have an air leak, which in conjunction with choking, sends both lots of fuel and air to the engine resulting in the racing. its gonna be hard to check for with carb spray if your bike wont run smooth for any length of time. i dont believe your its your cap vent as that should allow you a few minutes of normal running. one other thing to try to be sure the fuel is flowing is to open the screw on the bowl and make sure it flows freely(wont be really strong) for a little while.
Quote
Share

Robert Timothy
Robert Timothy

October 22nd, 2009, 9:13 pm #4

There is a passage after you remove the float bowl that gets missed almost every time someone attempts to clean the carb.It's underneath and hard to find.
But you might have a cap not venting like in the lower post where i told him to clean petcock and make sure the cap is venting.
Also replace a spark plug at the first sign of trouble.
If you have an air inleakage,you can find that by spraying carb cleaner at connections of carb to intake,intake to engine,or cylinder base to block.Do this when the engine isn't too hot,and notice for any roughness or rpm changes down or up.
Your carb is WAY smaller than a 28mm,so don't try that. don-ohio
Hey, interesting problem. Have you tried removing the express carburator? My guess is that there could be something clogging up the fuel in the line. You should try taking apart your honda express carburetor and cleaning it. You could also try removing the plastic express moped filter on the honda. I just bought a 1978 Honda Express myself and love working on it. Well, good luck and enjoy your honda express moped!!!

Good Luck,
- Robert
Quote
Share