Moped Qestion by a Noob - Yumbo Free Idling

Hi, I've been a moped user for the past three years now, but still a pretty big noob when it comes to mopeds and mechanics in general. I have a blue Yumbo Free early 2000s model that's been having some trouble this year with idling. Every time I am out to ride and I have to stop at a stop sign or traffic lights, my moped almost immediately stops idling and stalls. I have to keep hitting the gas and choking it a little to keep the engine from stalling every time I stop the moped.

I think I'm supposed to open her up and just adjust the idle screw, but I am having trouble finding it. I thought that may be the most logical cause of the problem. I could upload photos of my carburetor to help identify it.

Any help would be appreciated!

Thanks,

Tom

Re: Moped Qestion by a Noob - Yumbo Free Idling

Downhill Harvey (OFMC) /

Have the bike running on the center stand, then hit the rear brake, if it stalls, the clutch is sticking.

Re: Moped Qestion by a Noob - Yumbo Free Idling

Adjusting the idle screw is probably the solution

Re: Moped Qestion by a Noob - Yumbo Free Idling

Brent Bublitz /

If hitting the choke keeps it running, the idle screw may not be your only problem. Needing choke on a warm motor implies that you are running really lean.

Pull the spark plug and compare it to the various charts floating around. If you are running lean, then you need to rejet your carb. You can cause some pretty bad engine damage by running lean.

If it's just low idle speed, then finding that idle screw sill solve it.

Don't mess with a lean running motor though, fix it right before something bad happens.

Re: Moped Qestion by a Noob - Yumbo Free Idling

I tightened the idle screw, and I'm still having problems. Maybe I should clean the carburetor more? I removed the float bowl and removed any excess oil/particles that were there. I'm not sure if I am running lean. My moped will run fine every time I take it out. It's just having the motor run idle while it's not moving is the problem. And CORRECTION, it's not the choke, its the Engine Stop Lever that I keep pushing on the left handle to make it work. (edited)

Re: Moped Qestion by a Noob - Yumbo Free Idling

You may have not only an idle speed screw, but an idle mixture screw. Check for that. If you still have problems, the idle jet/passage is likely clogged.

Re: Moped Qestion by a Noob - Yumbo Free Idling

Love them yumbo's

The carb is a mikuni clone with idle and air mix screws.

As with any problem tuning, start with a fresh plug.

Take the right side cover off, the carb is under there.

Take the carb off, clean everything!!! with carb cleaner and compressed air. This is a three circuit carb, take all the jets out and clean them and clean all the passages. Its an enrichment choke, so make sure it's functioning properly. move the lever back and forth and see if it's moving, and the spring is not binding. Those carbs are kind of shitty.

The idle screw is the one with the spring on it, the air mix sits in flush.

Turn the air mix screw all the way in, count the turns if you like. Then turn it back out, 1 1/2 turns is good.

Crank the bike up, turn the idle screw in until it will idle. If it has to go all the way in, then turn it back out one full turn and turn the air mix screw out 1/4 turn at a time until it idles.

Also make sure the air box is connected properly.

If it's still not idling, then you should check your clutch. as harvey said. You can take the clutch off and take the starter clutches out too, Kinda stupid to have them since its a kick start.

If none of that stuff works then I would look at like your intake to see if you broke a reed or check out your seals. Could be time for a rebuild.

These motors are really cool they're like a peugeot/av10 mashup you could prob fit a av10 kit on there and variate with a little work and it would really rip

Re: Moped Qestion by a Noob - Yumbo Free Idling

Downhill Harvey (OFMC) /

Tom Duffy Wrote:

-------------------------------------------------------

> I tightened the idle screw, and I'm still having

> problems. Maybe I should clean the carburetor

> more? I removed the float bowl and removed any

> excess oil/particles that were there. I'm not sure

> if I am running lean. My moped will run fine every

> time I take it out. It's just having the motor run

> idle while it's not moving is the problem. And

> CORRECTION, it's not the choke, its the Engine

> Stop Lever that I keep pushing on the left handle

> to make it work.

...............again, does it idle fine on the center stand, or do you not have a center stand. If it idles fine on the stand, quit fucking with the carb, and investigate the clutch.

Re: Moped Qestion by a Noob - Yumbo Free Idling

Thanks for the help everyone! I had to do a very thorough cleaning of every little hole and crevice in the carb before it started to idle again, including the hole for the idle screw with the carb cleaner I bought. Runs better than ever now. This noob is happy.

Thanks!

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