50cc GY6 electrical and running problems. By vegas50ccrider (Read 1,184 times)

[vegas50ccrider]

Hi guys, long time lurker here. I stop in and check what's going on sometimes and also come see if there are similar problems to what I experience when I'm working on one of my scoots or someone elses. I haven't posted in the New students thread yet but will make my way over there soon. I've been a mechanic for 40 some years and have done just about everything except officially work on aircraft systems, I've been working on scoots since early 2007 when I bought a Tank from a buddy at the bar that had 24km on it. Proud to say the green machine has close to 20,000km on it now with nothing major screwing up and regular maintenance done by yours truly.

The issue right now is a neighbors JMStar Powersports bike that he brought to me when he found out I work on them. It has some electrical issues that can wait for now but the main problem is the damn thing won't keep running. After tearing the wiring harness apart and fixing some shorts it no longer blows the fuse coming from the switched 12v DC side of the ignition switch and I can use the start button to get it started. Once it starts it revs to around 5 or 6 grand and slowly drops to around 2500 at which point it dies. If I play with the throttle while it's running I can get it to run a little longer but it will still die soon. Getting it to keep running is essential so I can then figure out if the stator is bad because I'm getting various conflicting readings with it running fast then dying before it settles out.

I know from reading and searching that JR is a master at wiring and some of you other regulars are outstanding with diagnostic advice so please help me out if you can. I know very little of the history of this bike due to language differences and the fact that Armando doesn't know much about mechanical jargon. It has had some work done by the dealer he bought it from (the butchered wiring harness tells me ALL kinds of things about them). It was built in April 2011 and has 2123 km on the odometer but he said that didn't work for some unknown period of time.

I have posted a short video on YouTube and will try to link to it.
Sure hope someone can help me out. BTW I did clean the carb which he said was new but had a blocked idle jet and am prepared to adjust the valves if it's thought necessary. Thanks in advance and you guys have some cool smilies on this site.

Harpo

PS sorry for such a long post but I tried to get the essential info in here but am ready to add any more that's needed.

[JR]

I've got a 50cc also by Jmstar and even when brand new it had the same issues. It was a trainer for my stepson to learn on and when he moved up to a bigger scooter has not been run since. I actually have it on my motorcycle lift now, put a new battery in it and am going to get her buzzing again to use when my wife and I go camping this summer to just buzz around on at the camp area and to run errands.

First this is check the intake manifold for leaks and the manifold itself, they are cheap and the slightest leak really effects these 50cc scooters. Downdraft fuel feed or fuel pump? Got to make sure it's getting good fuel flow on the idle, sounds stupid but when revved up it has a lot more vacuum. Yes adjust the valves, that's a must. Low speed jet, if it has the slightest amount of anything that restricts it, she'll not idle for crap.

We're here to help.

JR

[vegas50ccrider]

Thanks for the response JR, this thing is driving me nuts!
I replaced the fuel line and filter from the tank to the vacuum fuel valve and the damn thing won't start again. Yesterday I was only getting spark sometimes and it seems it's back to doing that again. There is power from the stator to the cdi on the r/b wire but no pulse on the r/w wire. I'm pulling the fan and flywheel again to see if there is something loose.

Edit

OK pulled the flywheel and wiped out the dust again and it started right up, revved to around 3500 rpm and barely climbed from there when I played with the throttle then it died again.The EGR system is sucking air so I think I'll just cap that off at the head for now.

[vegas50ccrider]

OK adjusted the valves and she runs halfway decent, a little more tuning and that should be taken care of.

The electrical is still an issue, having read a bunch on here I'm thinking the stator is shot since the voltage readings between the green, yellow and white are all supposed to be similar from what I understand. Right now I have 20.5v between g/y, 23.9v between g/w and 3.7 between y/w. Those numbers bounce around a little while it's running but that's an average. Could this be the reason I don't get a trigger signal sometimes?

ScrappyDog is just down the road from me so I'll go pick up a new stator if need be.

[alleyoop]

It is a little LEAN the rpms bounce a little at idle, give the fuel ratio mixture screw 1/4 to 1/2 turn counter clockwise.
Alleyoop

[tvnacman]

tvnacman.blogspot.com/

Your overheating it as well , you have the fan off and the fan shroud too .

John

[vegas50ccrider]

I didn't run it very long guys and there was a good breeze through the garage.
Changed the stator and now I have good voltages and tweaked the carb a bit more and she sounds sweet now.
It's nice having ScrappyDog within a 15 min ride from the house and when I walk in they say "What are you working on today?" LOL

[vegas50ccrider]

Got the wiring harness all put back together and started putting plastics back on. I had to make a few tabs for mounting a couple broken pieces but it should be back together and test ridden by late this afternoon.

I'd like to say thanks for having such good resources such as wiring diagrams on here.

Keep the shiny side up and your knees in the breeze.
Harpo