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Motor Scooter Problem

I have a 2008 “Lance Charming” Chinese motor scooter with a 50 cc 1 cylinder engine. It basically looks like a cheap Vespa knock off. The first two summers I rode it, it worked more or less fine. This year, I took it out winter storage, gave it an oil change, then took it for a ride. I rode 8 miles away from my home with no problems, stopped for two hours then turned around to ride home. About 5 minutes into the return trip, I think I hear the sound of metal clanging against the pavement behind me, but I’m not positive. From this point on in the trip, every time I come to a stop at a light or stop sign, then try to go again the engine stalls out. Each time it stalls out, it takes increasing longer to get it restarted. The first time it did it, I got it restarted in about 10 seconds, however when I was half a mile from my house, I had to pull over to the side, and took me about 4 minutes of trying before I could get it going again. This thing has both an electric start, and a kick start, and neither one of them were working.

Since then, it’ll start fine when cold, but once I let it warm up even for 5 minutes, it’ll have this same problem of stalling out. If anyone knows if I did lose a part that is causing this problem, or was that just in my head and something else is causing this staling out, it would help me out a lot. Thank.

That sound may have been road debris you ran over. Have you confirmed this thing still has oil? Is it liquid cooled? Does it still have coolant?

If it is not fuel injected, I would have someone check the carburetor.

About 5 minutes into the return trip, I think I hear the sound of metal clanging against the pavement behind me, but I’m not positive. From this point on in the trip, every time I come to a stop at a light or stop sign, then try to go again the engine stalls out.

Let me take my shot at diagnosing something I know almost nothing about (i.e. looking like a fool):

I’m guessing this is an automatic (no manual clutch–most small scooters are). I’m guessing the metallic noise, followed by stalling out at stops, was the centrifugal clutch self-destructing.

This sort of a clutch (often found in chainsaws, just like your 50cc engine) are designed to disengage at low RPM and engage at high RPM. I suspect your cent. clutch is now toast, and not properly disengaging at low RPM.

This is all theoretical, really, when one is talking about a “disposable” mode of transportation.

It does still have oil, and it’s air cooled, so no coolant needed.

It is an automatic, and it is when I try to get it into first gear that it stalls out on me, however, it’ll work fine when it’s cold, these problems only happen when the engine has warmed up, and as I said the warmer it gets, the worst it gets. Also, it should be starting into neutral, so I’m not sure a bad clutch would prevent it from starting when it is warmed up. Thanks for the suggestion though.

First of all, these machines have a belt drive with a variator at the engine and a centrifical clutch with a variable pulley at the back. There are no gears in the “transmission”. There is no neutral or first gear. A clutch problem would not cause this complaint.

Your problem seems related to the cold start circuit. In many scooters there is a system using a thing called a bystarter that allows a rich mixture when the engine is cold, but shuts off the rich circuit after running a while. If that bystarter gets disconnected or fails the scooter will start fine when cold, but run lousy after about 5 minutes, get poor gas mileage and have poor power. It might even show oily black goo on the back, from the exhaust.

This is a “disposable” scooter with absolutely no factory support. It was very cheap to buy, and for good reason. If you want to keep riding a scooter you can choose to learn to be a mechanic, you can search for a local scooter mechanic (but I would not spend much money on this machine), or you can give it to a charity or young person who wants to learn about machines. Then go find a real scooter. There are the usual Honda, Yamaha, Vespa names, and there are a few others like Kymco and SYM that are reasonably reliable too.

Scooters are wonderful, economical and liberating machines, especially in cities, and there should be more of them. Unfortunately the past administration allowed an influx of faulty, uncertified and unsupported scooters to come in from China, and this is one of them.

That sound about right with the cold start circuit, as it runs fine when cold, but after about 5 minutes is when it starts to have problems. I have no problem fixing the scooter myself, I just was not sure what the problem was. I’m posting the question here, as I refuse to pay anyone to actually work on the scooter since one of my reasons for having it is to save money.

OK. The bystarter is a cartridge shaped thing with two electric connections. It’s attached to the carburetor, usually with a couple of screws. If you remove the screws and the retainer ring it should pull out with some resistance, because there are rubber ring gaskets around it. When it’s out it will have a point on it. That’s a needle that goes into a secondary jet in the carb. If you search EBay for “bystarter” you will find pictures of them for Hondas. If the bystarter is cold, measure its complete length right to the point of the needle. Then connect it to 12 volts and wait about 5 minutes. It should get hot and get longer by about 3/8 of an inch. If it does not get longer, it is broken. If it does get longer it is working. Then you have to put things back together and be sure it gets power, which will only happen when the engine is running. Not just on. It has to be running, because the power to the bystarter comes straight from the stator (generator).

Depending where you live you might be able to get by well without the thing. If the start temp is never below 50 or so, or you keep it in a garage, you can try. That means you have to remove it and then figure a way to plug up the jet and the air passage that starts in the front of the carb, crosses the jet and empties out in the back of the carb after the throttle plate. I’ve seen people plug up everything with epoxy putty, which is pretty drastic unless you have a spare carb. You can separate the brass fitting and needle from the bystarter, drop them into the hole, and create a plug for the large hole where the bystarter was.

I’m sorry but your wrong I’ve been a mechanic for 15 years and u have it backwards when a cold start sensor goes bad its hard to start when its cold. that’s why its called a cold start sensor.

This could be a few things but first i need info. Does it just die when u stop or when u stop does it still want to pull does it feel like its pulling. If so then ur variater or the clutch is bad. If it does not pull when u stop at a idle then its 1 of 2 things its your Coil or CDI box. When a coil gets hot it will stop firing until it cools same with the CDI box. But the cold start sensor is definitely not bad unless its hard to start when the engine is cold when i say cold i mean if u just ran it for a while then it must cool for hours. or when u get up in the morning and try to start it.

It would actually idle fine when I stopped, and it didn’t pull either. It wouldn’t stall out until I tried to accelerate again. Then after it would stall out, it would not restart easily. I would usually need to let it sit a couple of minutes before I could go again. One guy told me it was a bad clutch, so I replaced the clutch, that still didn’t fix the problem, in fact it actually made it worse. After replacing it, I could not get it to start at all even when it was cold. I ended up having to sell it as I couldn’t find anyone in the area that works on them.

On scooters the bystarter system is used to start cold engines. It has a separate air passage that goes from the intake bell of the carb, around the entire throat (venturi) area, and opens after the throttle plate. The electric bystarter has a needle and shaft, and it extends when powered and shuts off the secondary air passage and jet. Believe it or not, there’s a pellet of wax that expands with heat inside the bystarter, and the heat comes from electricity taken directly from the stator. It’s a screwy system, but it sort of works. If it fails it almost always makes for easy cold starts and very hard hot starts because the bystarter does not extend .

Scooters have rollers and a vbelt. I suspect this is a carb issue. If you let gas sit in it over winter the gas may have varnished then when you run it and get it warmed up the gummy stuff in the carb expands and blocks the fuel causing it to cut out. Cheap scooters are generally crap…spend two or three hundred more and get a honda metropolitan. They are liquid cooled and four cycle. Runs forever. I have had mine four years and it is great, Never had a problem

Before riding it for the year I put in a new tank of gas, and it wasn’t until after riding it for about 8 miles that the problems started. I tried throwing in a new carburetor before selling it but it didn’t help at all.

Check the manual for valve adjustment specifications. They may be too tight.