honda express can't slow down

this is my first moped and i've never really worked on them before so apologies if this is an easy fix i couldnt find any info

i took the carb apart and cleaned it out cuz it wasn't running. now when i put it back together, and start it, i turn the moped on and dont touch the throttle at all... but the starts going crazy and running at full speed. i tried turning the throttle screw like 3 full turns (u can see the spring that wraps around the screw) and it still wont slow down to idle. i have the air screw out like 2.5 turns. seems as though no matter how far i turn those screws, it wont slow down. any ideas on why i cant get this thing to slow down?

i almost ran myself over the first time... the wheel was on the ground and it just started going out of control

Re: honda express can't slow down

oh and it's a 1978 Honda NC50 Express

Re: honda express can't slow down

Auto, you remember that tube that came out the top of the carb when you took it apart? The one that is connected to the throttle cable? The gold colored metal tube that lifts up and down when you twist the throttle?

Well, that diddnt go back in right. Either you are missing a spring, or it is in sideways. If you are missing a spring, then yourthrottle grip will have no tension, in other words, it will just be loose.

That tube must be pointing in the right direction when it goes back intot he carb. There is a little notch running up the side of it. That must match up with the little bump that sticks out in the hole it goes in. If it dosnt match up, the slide will only go halfway in, and get stuck. You will still be able to screw the top of the carb on, but it wont work.

This should be easy to fix. You dont even have to take the carb off. Just unscrew the top part of the carb. the part where the throttle cable goes in. You should be able to pull out the slide tube. It has a needle at the end. Now notice that on that tube there is a notch running the entire length of it.

Now look down into the hold it goes into, or feel in there with a clean finger. you will see or feel a little bump that sticks out. That is suposed to line up with the notch on the slide tube. It fits inside the notch, and the tube is kept straight with that bump.

Also note that the needle at the end has to fit into its hole in the bottom of the carb. Usually slides right in, but sometimes it needs to be wiggled.

Now make sure that slide tube goes all teh way down, and screw that cap back on.

Now if you take off the air filter, and look into the carb, you should be able to see that slide, and it should be blocking the passageway. If you twist the throttle, it should raise that slide up.

NOTE: The only thing that your idle screww does is raise and lower that slide tube about 1mm. Thats how you adjust the idle. The higher it sits, then the more air gets through and the faster it runs. the lower it is(idle screw screwed out), the lower the slide sits, and the slower it runs as less air gets through.

LEt me know if you need any more help.

Re: honda express can't slow down

Oh, and post this in the Repair forum, or it will get ignored. Just a tip for next time.

Re: honda express can't slow down

awesome... i'm gonna try that out. i appreciate the help!

and yeah i noticed i posted in the general section after i posted this. will post in repairs next time. if someone can move this to repairs i would appreciate it.

Re: honda express can't slow down

or u have an air leak, but didn't u have breaks. or r u like me and adjust those after u figure out u need them going 35 down a road with no way to stop and a end very close always, fun :P

Re: honda express can't slow down

Yea, I assumed because he just took the carb apart for the first time that that was the problem, but could be a bad air leak. Did you make sure to clamp the carb on tight when you put it back on?

Re: honda express can't slow down

Steve Williams /

slides in wrong,absolutely guaranteed.

Re: honda express can't slow down

Yea, id like to hear an update.

Re: honda express can't slow down

I think that was the problem. I put it in the right way I believe now and it's running pretty good. it slowed down the throttle a good bit. but the wheel still spins when i have it up on blocks when i'm starting it. i think i noticed it will spin slow and then gradually speed up. tried messing with the throttle screw and got it as good as i think i could get it (even though i'm not sure how fast the wheel should be spinning while doing this..i'm guessing as slow as possible).

i think i also noticed the choke cable wasn't screwed into the carb very tightly i tightened that up and i think it started running a little better.

the only thing now is when i'm riding around and i stop for a few seconds it dies. like if i hit a stop sign and somebody walks in front of me (stupid pedestrians) and i have to stop for a little bit, it will die. i guess it's not idling correctly. then i have to kick start it a few times and get it going again. any idea what could cause this?

Re: honda express can't slow down

i also noticed on the throttle pin thing, there is a small notch on one side, and then there is a gap that runs all the way down the side of it on the other side... i believe you said to use the gap that runs all the way down the side of it to fit on the bump, and not the smaller notch, right? that's what i did.

Re: honda express can't slow down

i'm reading this under "final running adjustments" and getting some good info... i think i need to mess around with it some more. but if you have any other tips from what i wrote earlier i'm open to help!

Re: honda express can't slow down

where is the idle mixture screw? is that the same as the air mixture screw?

Re: honda express can't slow down

that should be the screw witht he spring around it.

Re: honda express can't slow down

just making sure there isnt a screw that i'm not noticing, cuz the article called the idle mixture the air screw later on...

i cant get this thing to idle like i want it to... ive been using the back brake slowly and using some gas when i hit a stop so it stays on... but if i brake pretty quick it will usually shut off. any tips on getting this little guy to idle right?

one thing that seems a bit strange-- when i have it up on it's stand trying to mess with the throttle screw, when it is idling, it seems like it will throttle itself for a few seconds, then slow down, then speed up, then slow down to an idle.. and sometimes just shut off when it slows down again. maybe this might be causing some of my problems...?

Re: honda express can't slow down

It is supposed to do that. It is warming up. After about 15 minutes of running it should stop, and idle at a constant.

let it run for about ten minutes or so befroe trying to adjust the idle.

The "Mixture" screw dosnt need to be messed with. I dont even remember where it is actually.

Just mess with the idle. you want it so that when its up, it will just barley start to think about turning that rear wheel.

As far as it dying at stop signs.... Could be a lot of things. This hasnt been ridden in a long time right? This might go away. 2 cycles like to be ridden, and run. YOu might need an oil change for the clutch to be rid of all water and other contaminants. It could be dirty crank oil.

Also, the engine will do this when its not warmed up. I would imagine if you drove for 20 minutes it would not do it anymore. Is that possible?

Re: honda express can't slow down

well there's 2 screws next to each other.. one i believe is the throttle stop screw (the higher one that i believe you are referring to as the "idle") and then there is a lower one called the air mixture screw in the article... then later on it says this in the FAQ:

_" The bike is nearly impossible to start, it takes a very long time and even once it does start will not idle very well until it is warm.

o Try turning the idle mixture screw in slightly. 1/8th-1/4th turn.

The bike starts and idles, but bogs down/dies as soon as it’s given gas, especially when warm.

o Try turning the idle mixture screw out slightly. 1/8th-1/4th turn. "_

and also

_"You can also try adjusting the IDLE MIXTURE SCREW if your bike still won't idle well. Turning it in makes the idle mix richer (more gas) which is better for cold starting and idling with the engine cold. Turning it in too much though will also cause problems. Turning it out will result in a leaner mix. This gives a better warm idle and can solve problems of bogging down when accelerating from a dead stop. 2 and 1/8th turns is simply what my bike runs well with. "_

I was just wondering if it's talking about the higher screw or the lower screw or something else altogether. i'm guessing it's talking about the lower screw.

i had it running for about 45 minutes to an hour, came home and tried to mess with the throttle stop screw some more while it was on blocks and i'm pretty sure it was still doing the thing where it speeds up and slows down.

and yeah it was turning off toward the end of my ride when i would hit a stop... at that point i think it was pretty warm.

it hadnt been ridden for about a month is what the guy who i bought it off said. ive been riding it around the past 3 days or so pretty good.

thanks for the info and ideas.. i appreciate the help

Re: honda express can't slow down

Im not sure which is which wither. If you post this pic in the repair section with a new topic, you will get an answer. This is your Carb. From Scooters are listed under Motorcycles, and not under scooters. I dont know why.


Re: honda express can't slow down

This is a good site dedicated to the express. You might find some info from checking the mesage boards.

Re: honda express can't slow down

Nevermind, this one answers the question. See attachemnt


Re: honda express can't slow down

So the top screw is the Idle screw, and the bottom one controlls the mixture.

All the idle screw does remember, is raise the slide up and down about 1 mm.

The mixture is screw is going to add and take more gass fro the mix making it rich or lean.

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