50cc Scoot dies at stop light By beo111 (Read 1,866 times)

[beo111]

Well I haven't had a problem in a very long time but one has finally come up. After this winter season I had to take the carb out of my 50cc Peace scooter and clean it up in order to get it running. I also adjusted the valves last week to .003 intake and .oo4 exhaust which is the settings I've kept for 4 years. I've had the same gas in there since last season and put Sta-Bil in to hopefully keep the gas fresh. Well I got the scoot running, but when I get to a stop light on the street the bike shuts off or the rpms drop really low to where I have to give it throttle in order for it to not shut off at the stop light. It then goes back to the normal idle. I've never had to mess with the air/fuel mixture screw (it has the brass cap over it so I'd have to break it off) even though I've had the bike for 4 years here in Wisconsin, so I don't want to touch it unless it's necessary. I guess I'm wondering if this is a carb problem, engine problem, or a bad gas problem? I'm gonna drain the gas out tomorrow and clean the carb again, then put in fresh gas. Any help would be great. Thanks.

[Bashan]

I had just those symptoms on my Pegasus recently. I blew out the vent on the gas cap and all is well. It's worth a try. If you don't have a vent cap you'll have to check the vapor canister vent system and the check valve. If you're not going to use your bike for a month or so drain the fuel system. Sta-bil really doesn't protect that well.

[beo111]

Thanks for the response Bashan! Well today I took the carb out again and cleaned it thoroughly and drained out the old gas and put in fresh gas with seafoam. The problem is that the bike runs but the idle is inconsistent. I was going to adjust the a/f mixture screw and the idle, but while I have the bike on the center stand the idle goes from high rpms to low rpms. It happens by itself which is strange. I'll give it throttle for a second and let go, then the rpms go high for a few seconds then drop low again. Then it goes back up to where the rear wheel spins. Sounds like a carb problem?

[Bashan]

Here's Alley's prescription for a bouncing idle. I'd also check for vacuum leaks. If you're messing with the carb you can dislodge a line sometimes (pic for our newbs):

If they're OK it might be the intake manifold to head seal, or the carb to manifold connection.

[beo111]

Thanks for the info. Every time I think I'm getting good at figuring out my scoot problems something comes along that stumps me. I'll check for vacuum leaks and the intake manifold. I replaced all hoses when I first got the bike with Goodyear hoses because I wanted to avoid dealing with the cheap hoses deteriorating. I'll let you know what happens by the end of the week.

[beo111]

Well guys, with all of the symptoms I did narrow it down to the carb. I just decided to purchase a new carb and put it in now it runs like a champ. The idle is smooth and bike feels great on the road. I cleaned the old carb twice and didn't want to put it back in a third time to have it fail. Not sure what went bad on the old carb, but a buddy of mine said he heard that the a lot of people have trouble with small engines because of the ethanol in the gas. I don't know if that's true, but I sure won't put Sta-Bil in my tank anymore. I drained out the old gas and glass filter then put new gas in with Seafoam. I hope all goes well in the future! Thanks for all the help!