1980 Express NC50 - Idle will not hold. constantly going up.

stefano bernardo /

I Have had my Express for about 2 months now and everything has been going great until recently. For some reason the bike will not keep it's idle where it was set.

I set the idle to right before it stalls and then raise it a bit so it's not lumpy. Rear wheel doesn't spin and all is good. After I take the bike out for a spirit ride and get it up to 30+ MPH for some reason the idle will end up being higher than prior to riding.

When I get off the bike after riding it for a bit it just runs away and the idle is super high, after it's on the kick stand the rear wheel starts going off the races.

I have reset the idle a bunch of times already and every time it does the same thing.

Any ideas? Starting to lose my mind.

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

Always set the idle hot. What year is the bike, auto choke or manual. Have you set the idle air screw as it is just as important as the idle speed adjustment.

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

stefano bernardo /

It's a 1980 with the manual choke.

Bike was hot when I set it to be sure.

Basically I followed the steps that have been listed in a tutorial on here.

Set both screws all the way clockwise then turned air screw out 2 1/8 turns and idle screw 1 1/2 out. that literally had the bike running at like open throttle. So i set the idle screw back until it wouldn't stall and adjusted the air screw to smooth the idle out a bit.

Took it out for a ride with the idle barely above stalling, came back and it was far above where i set it, so much so that the rear wheel was spinning while it was on the stand. (edited)

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

You still need to tune the air screw, stock is about 1 1/2 and start from there to find highest idle. Then set the speed with the other screw after.

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

stefano bernardo /

Ok, so basicallyI do this:

1. Set the idle to the "stock" settings then after the bike starts use the idle screw to set it to the lowest idle speed.

2. After that I use the air screw to find the highest speed, correct?

3.Once that is set than I have to use the throttle/idle screw to set the idle speed.

Sound about right? Can an incorrect method/procedure cause the idle to raise while riding? Just want to make sure it's not the carb or anything else.

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

not the lowest idle. an high type idle. whoever wrote that should be shot

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

You set the idle to a slightly elevated speed from what you would actually run, then you adjust the idle air screw to find the highest idle speed from what you have set (elevated). If the idle rises drastically, lower it to the point that you started from and continue trying to find the highest (this is basically narrowing it down to a very fine margin) idle speed again. Once you have found the absolute highest idle using the air screw when starting from a set idle speed, then you are done and can adjust your idle down to where you would like.

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

stefano bernardo /

OK, I managed to get the idle to a some what normal level. However, there are more issues now than before.....sigh

1. The bike will idle fine but after running it at a high speed for an extended period of time it will simply die out when I stop and will take 4-5 tries to get it started again, I will also have to watch the revs to keep it from stalling again.

2. The rear wheel will NOT stop moving when on the stand. No matter what I do no matter how low the idle is it will always move. It wasn't an issue when I first got the bike and was driving it around but has all the sudden started doing it.

Really starting to lose my patience with this thing as there isn't much in the way of reliable information to use to get it working again.

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

Sounds as if the clutch is sticking, which will cause both problems you mention. Otherwise dieing after continuous high speed running could be lack of compression or improper idle mixture/idle speed.

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

Okay.....I remember working on a Honda Express that acted somewhat like what you're describing.

This was years ago,but I remember a very hard to spot hole that must be cleared out. It is toward the edge over from the needle valve hole if I remember right,and you don't see it unless you look for it up under there.Check it out.

If you find it,run a fine copper wire thru it and spray carb cleaner thru it.When it's clogged,your symptoms happen. don-ohio (:^)

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

Mine is having the same issues. Do you adjust the screws with full choke or no choke?

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

No choke, obviously. You adjust it in the operating temp, normal run configuration.

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

matt boda1nz /

Carb clogged or air leak.

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

Have you looked to see if the spring behind the screw may have collapsed? Note the exact position of the screw after you set it, ride and check the position again. Is it actually movingdue to vvibration and a spring not holding it?

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

you must pull out the long copper tube on the side of the jet with a small pair of pliers then clean the 8 small holes on the tube witch is your idle jet with a small copper wire then tap it back in this will solve your idle problem mine did the same exact thing and its fine now

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

Steven thank you so much. I was having a idle problem after cleaning my carb three times. I did as you said and it worked great. Thanks, Matt

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

No prob..

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

Kiel the Canuck /

NC50 carbs are decent little things, but they do collect dirt like a magnet. I had to clean mine half a dozen times before it would start every time

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

How the hell do you get the tube out. I've tried pliers and heating it up but no luck!

Re: 1980 Express NC50 - Idle will not hold. constantly going up.

The spring isn't holding it still like it should.

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