Moped Tech

[calvynandhobbs]

I don't know much about my Yumbo C110 that I picked up a couple years ago and I know at least one of you, maybe more work on mopeds and the like.

Last fall I came around a corner and when I went to give it gas it died and would not restart, it only cranked. I put it away for the winter and now it's time to get it running.

I had a spare 5 pin CDI and Stator so I installed those. It's got spark. Fuel is coming out of the tank fine, but I don't think it's getting into the carb. I took it all apart, cleaned it and it started right up, but at wide open since I put the throttle cable into the carb wrong. LOL Fixed the cable and now it won't start even on starting fluid unless I let it sit for a while with the fuel shut off. Then it will start for a few minutes and die and not restart again.

I don't see any pin holes in the float, but what are the chances that it's got a hole and is shutting off the fuel?

[HeavyMetal]

Dillon (Hydra) better get in here

[Lycaon]

[Henchman]

[calvynandhobbs]

I played with the float a little and it has some gas in it. For the price of these cheap carbs I'll order another and put it in.

[CSaddict]

Moped carbs are cheap. Replace it. They use the GY6 motors in most new mopeds. I am very familiar with it because its also in my kid's dune buggy. Is yours the GY6 type?

[calvynandhobbs]

Mine is a 110cc Honda cub clone made by Yumbo. It's a 4 speed semi-auto and the entire bike looks just like a Honda Wave. Here's a pic of what the motor looks like.

[Hydra]

Those 4t Honda horizontal motors are super simple, but not as simple as most 2t motors.

You cleaned the carb and you say the slide was put in wrong so it was at full throttle... any chance you left a bunch of carb clean in the bowl and it fired over with that but was still cloggeg?

Good way of checking is to pour a couple cc's of gas straight into the plug hole and seeing if it wants to run. It sounds to me (and judging by the common problems/qualities of those engines) like you carb is just really jelled up. If you didn't remove all the jets from the carb and clean them out with a loose bit of guitar string/wire, do that for sure.

Also, I believe you're running a keihin or mikuni carb, usually with a round/symmetrical bowl. Alot of times you can put the bowl on backwards and lock the float up which will cause weird issues after you think you've solved the actual problem.

REPORT BACK ya hEARD

[Hydra]

Between the GY6 and the HZ motors, they both have cheap replacement parts. And as you are basically replacing bad clones with bad clones, there's no harm in using ebay cheapos.

Of course, you could upgrade the carb to a true Mikuni VM20/22 if you wanted to go through jetting and such.

[Hydra]

The one time I have an answer and I feel unfulfilled...

[calvynandhobbs]

I do think it was running off the carb cleaner and starting fluid. Didn't try putting any in the spark plug hole, but there probably is still trash in the jets. One test I did was take the float out and put it in some gas with a small weight. I could see bubbles coming up and the float was sinking. For the time for me to mess with it I'd rather just replace it with another cheapy carb. The first one lasted 14 years and about 7k miles so if I can get that out of another cheapy I'll try it. LOL

[Hydra]

I hear you on that. All those cheap carbs have a short life span. Where as the 30+ year old carbs that were made in austria or japan will outlast the rest of the gaskets and rubber on the bike

[calvynandhobbs]

I need to learn these small carbs. New one came in so I installed it. Will now start with starting fluid and will continue to run on gas as long as I keep the RPMs up with the throttle. It won't idle and when it dies it can only be started again with starting fluid. I thought I read somewhere about a vacuum in the carb that keeps the gas flowing. Help

[Hydra]

The vacuum stop is usually only at the petcock, where the petcock shuts off automatically more or less when the carb isn't drawing.

The first thing I would do is take all the jets out of your original carb, clean them with carb clean and a single strand or wire/guitar string (carefully), and then put them in the new carb.

100% it seems like the jetting on the new carb is wrong, which is typical because carbs just comes with generic jetting. DO NOT take both apart at once, at the same table. MOst likely the jets are unnumbered and you'll mix them up. Take apart the old first, mark the jets from that one with a file scratch along the head. THEN, take em apart.

I bet that'll get you back to normal.

[calvynandhobbs]

I didn't even think about the jetting being wrong on the new carb. My wife has me too busy with other things around the house right now, but I'll take a look at it soon. Now that it's starting to warm up I'd like to get it on the road.