Scooter/Moped won't start consistently

I recently bought a used 2005 Yamaha Vino 125 cc scooter. It runs relatively well, but has a problem starting sometimes. It seems like it just won’t “turn over.” It starts to rev up but then kind of sputters and dies. Usually after several tries I can get it started, but sometimes it just won’t get going. It seems worse when it is damp or has been sitting for a long time.

Is this the spark plug (there’s only one)? There is a new battery in the scooter.

It’s certainly worth $2 trying a new spark plug. Look in the owner’s manual to see what plug to buy and make sure the gap is set correctly.

If this were a car and moisture affected the problem, I’d suggest plug wires but I’m not sure your spark plug wire is replaceable.

It sounds more like a fuel delivery issue though. After sitting for a time, there’s not enough fuel getting into the carb and into the cylinders until it’s cranked for a while. After you park it, any chance you notice that gasoline leaks out of the carb?

You say it runs “relatively well.” Does this mean that it doesn’t run too great? Try a new spark plug. Otherwise your carb may need a little work; cleaning it out or adjusting it. Carburetors don’t like to be left sitting with old gas in them for long periods of time.

The fuel delivery issue seems like it might be a fit, actually. Sometimes after it does start it’s still a little sputtery and I do sometimes smell gas. I thought that gas might be leaking when I first bought it and I don’t seem to get the mileage that I’m supposed to get.

Ethanol is hard on carburetors, especially if the gas sits in the carb for a long period of time. It makes the gas go bad quicker and eats away at gaskets. Non-oxygenated gas would be better.

If you can access the carburetor, make sure the nut underneath the carb bowl is tight enough. (If this setup is still used in 05) See if you can notice where gas might be leaking.

Also, on terminology: “turn over” means that the starter works, engages the engine, which literally “turns” the crankshaft to start the engine. Thus, an engibe that doesn’t “turn over” has a problem with the starting system.

What you seem to be describing is an engine that “turns over” just fine, but fails to “catch” or fire. That would be a problem like mixture, timing, or compression. Is that right?

How experienced are you with carburetors? Idling okay, but stalling out when you rev it could be a lean mixture, or possibly water in the carb bowl. Draining the carb bowl on a 1-cylinder engine is super easy, and is what I’d start with.

Is this a two cycle engine? If so the spark plug is a definite suspect. They get oil fouled easily in two cycle applications. In any event, 4 cycle or 2 cycle, ask your shop to at least remove the spark plug and see if it is clean and properly gapped. As mentioned above, the next most likely suspect, common in small engines like this, is that the carb is dirty and some small but important passage partially plugged up. I had a dirt motorcycle and I had to take the carb apart and clean it out once in a while for this symptom. Sometimes the breaker points were the culprit too. Ask you shop to inspect them and verify they are set correctly and not pitted.

BeckyNissan, just to cover the most basic considerations: does this moped have an automatic choke, or a manual one?

Not using a manual choke, or an automatic choke that didn’t “do its thing” would explain poor cold starting. You said this is a recent purchase, and today, it’s possible you’ve never operated a carbureted vehicle. Maybe we’re all overthinking things.

You bought a 2005 scooter and if it still has the original tires please replace them even if they show plenty of tread. All you have between you and severe road rash are those small 10 inch tires.

You bought a 2005 scooter and if it still has the original tires please replace them even if they show plenty of tread. All you have between you and severe road rash are those small 10 inch tires.

And this will solve the starting problem?

PvtPublic- You are correct new tires will not solve starting problems. I saw the year of the scooter and that it has starting problems. I was concerned that the OP had purchased a scooter that had low mileage and had been setting in someone’s garage for sometime. I only made the comment because I have known people to take off on old unsafe tires on used motorcycles and scooters.

Hi folks, sorry for the delay in response. It sounds like what MeanJoe is describing in that it does start but then doesn’t catch. I do think that it sat for awhile unused with gas in it before I bought it and likely has been getting ethanol gas for a few years, so the carb build up sounds likely.

It is a four stroke engine, but I will also replace the spark plug to be safe. It’s an automatic.

Checking out the carbureter is probably outside my skill set (I am not handy), but I’ll get it in to a local shop this afternoon.

Thanks for the help, I’ll make sure I post a reply with what they find.

Also, MeanJoe is correct that I have never actually owned a carbureted vehicle before. So that’s new.

It probably has a choke that you can engage. Do you have the choke on while starting it cold? This could help it fire up on a cold start.

Good idea while they are working on the carb to ask them to install new fuel and air filters unless you know they are of recent vintage.

There are a couple of things you should check. First, if the gas you are using has been in there a long time, it’s not good anymore. You should drain it out and fill it with new gas. Second, if that does not help, you can try to figure out if the cold start system on the carburetor is hooked up right. They operate using vacuum hoses on Yamahas, I think, and if the hoses are leaky then nothing works right. The hoses themselves are just rubber tubes that often get cracks in them from time and weather. They are easy to replace, one at a time. If you replace the spark plug you will see whether the inside end is black and wet looking (meaning there is too much gas, the cold start is stuck on cold or the carb float is stuck).

Without knowing more about your skills it’s hard to help.

So, after keeping the scooter for a couple days (and of course it started up fine every time for the shop), they have an idea of the problem. The carb had been cleaned and the gas replaced, but there was a fair bit of sediment in the bottom of the tank that had likely gotten in while it was stored. The gas cap is on the top with this scooter, which makes sediment more likely to get in. There is also no filter.

The guys are going to remove and clean the tank and then install a filter for me and they think that should solve the problem.

They wouldn’t make a scooter without some kind of screen or filter between the tank and the carb. Now that your carb is clean, it’s probably unnecessary to do this extra work. Here’s probably what your filter looks like

If you don’t use this scooter very much, or it sits around unused for long periods of time, you’ll have better luck using non-ethanol gasoline. If you don’t know where to find non-oxygenated gasoline in your area, spend a little time on google and you’ll find a list of gas stations that sell it.

Well, so far so good. It’s been running great.

Goldwing, there was just a little screen at the bottom of the tank, no inline filter. That screen was pretty beat up, but the inline filter they put in seems to be working.