GY6 150 intermittent spark By scootec (Read 4,133 times)

[scootec]

Let me start by saying I understand the function of all electrical components and the wiring of the Chinese 150cc scooters. I read thru some of the stickies on no spark diagnosis. My problem is that the issue is very intermittent and hard to chase down. Basically I was driving the thing and it just died at idle. Wouldn't restart so I pulled off the road and after looking at it for a min it started. I didn't do anything. And that is now an ongoing problem. I replaced the plug, the coil, and I have 2 cdi boxes and the issue persists. It usually likes to die when it comes down to an idle but a few times it has flat out died while riding. When the problem first occurred it would run very rough with barely enough power to go 15 mph until it died but now that is gone and it simply runs great or does not start. Its very on and off, sometimes it dies and will restart immediately, other times it won't start. The only "trend" it seems to have is basically it shuts off when warm, then if I let it sit for a few mins it will restart. If it's totally cold it will run for 2 - 3 miles before it quits. Stator wire showed 77 Vac while cranking, the trigger wire showed .3 Vac while cranking. This test was done essentially right after it shut off one time. Also after replacing the coil I checked the V at the battery while idking at it showed only 11.9-12.1. I am leaning towards the culprit being the trigger/pickup coil.

[scootec]

The stator and trigger readings appear fine but because the problem is intermittent I don't trust them. Also I found the charging voltage of 11.9 volts at idle and barely anything more at 3000 rpm troubling, especially since the lights are just as bright as ever and get brighter as soon as the engine comes off idle. Plus the battery was totally dead before I jumped it and drove 2-3 miles and then it died, at which point the battery now had enough juice to crank for 15-20 seconds.

[cyborg]

Check the wires,, sounds like an internal wire break or a funky termination to me

[Bashan]

I strongly suspect your ignition problem is your trigger coil. They may test normal at no load but as soon as the bike heats up the coil starts to fail. I'd swap out the trigger coil and see what happens. They're inexpensive and easy to swap out. Try that first and then there's other things we can do but I bet that is your problem. Rich

[Alleyoop]

First thing I would do with those symptoms is Adjust Both Valves to .004 inchs before messing with anything else. Dieing after it is warm or hot and will not hold idle is a classic sign of valves to tight and loosing compression and no power. When cold some will run some will not all depends on how open the valves are being kept open.
Alleyoop

[Bashan]

Alley is spot on and I should have mentioned that. Do that first before you spend money on a replacement coil. I still think it's the trigger because you said you had an instance when it just shut off while riding. But Alley is correct, it could be valves and they don't cost a thing to set the gap.

[scootec]

OK I will check valves. I adjusted them about a month ago at .005". I should clarify that it doesn't simply die at idle every time or idle poorly. It will sit there and hold a nice idle and then just die all of a sudden. And when its running ill take off down the street and it has full power, runs great and then all of a sudden nothing in an instant. It shuts off so sudden it throws me forward. The trigger coil is my #1 suspect but I will look at the valves again. Has anyone removed a flywheel without the proper puller tool? The only way the trigger is sold here in town is with the stator so I may as well replace them both.

[jerryscript]

Check your plug boot. I had a similar problem last year, turned out vibrations shook it off and back on, making it an intermittent problem. Once I replaced the plug boot (had the orange performance one, put the stock one back on), I haven't had any issues since.

[Bashan]

Most of the vendors in the tile ads at the top of the site sell triggers without a whole stator. I would strongly urge you to get a puller, they are about $20.00 and you can get them on the same sites as the trigger.

[scootec]

I actually had that happen once so it was the first thing I checked, along with the vacuum line to the fuel valve/pump. Its a brand new coil and boot, connected snuggly on the plug. The bike is sitting at a gas station about 8 miles from my place. I'm about to go tandem on my friend's scooter to try and limp it home. I'll rum some more tests with my dvom, make sure it isn't fuel (would have to be a blocked inlet valve at the bowl) and then put his pickup coil on my engine and see if that fixes it. I am 99% sure its ignition tho because when it first crapped out my friend brought me a new plug and coil and when I installed it and tested for spark by cranking it over with the plug against the valve cover, it wouldn't light the old plug. It lit the brand new one but the spark was not strong. It was dark out and the spark still looked weak.

[scootec]

Update: I put my aftermarket cdi on so I could use the flashing led on it as a diagnostic tool. When the scooter does NOT run, the light still flashes. The only thing odd I found was the ground wire that goes to the coil has no continuity to engine or chassis ground. The terminal on the coil itself shows 6 ohms to ground with the wire disconnected. But the wire itself does not register anything to ground on the dvom. But it still runs sometimes. How is this possible?

[scootec]

Another update: trying to get it home and it died after 2 miles. Won't start. Before I drove those 2 miles the stator was making 83 Vac. Now it is making 15 Vac. Still getting .2 Vac from the trigger wire. So the stator itself is bad I guess? That seems to be the obvious problem. I'm just gonna do what I did before and put a DC cdi in it. My kick start is frozen anyway. Stators seem pretty unreliable I'm tired of dealing with them.