GY6 / ODS157FMI Won't start Turns over SLOW
 

I've got a GY6 /ODS157FMI series - 125 cc 4 Wheeler with electric start. (Raytech CT-125) The motor turns over slow like it has a dead battery so I replaced the battery with a brand new fully charged one and I get the same thing. I take the spark plug out and the motor turns a lot quicker without the compression obviously and gas is getting to cylinder but I don't think the motor is turning fast enough to fire. I have replaced the starter and checked valve clearances to .005 and .004 at TDC. Any ideas on what else could be wrong? It sounds like a dragging starter or a dead battery so I took the chance on replacing both. Fail 🙁 Before I dump more money in parts anyone have suggestions? Thanks

Take the plug cap off and leave the plug in. If the engine now spins faster, the spark timing is out, or the one way clutch for the starter is slipping. You can't alter the timing unless the flywheel has slipped on the crank but that usually puts timing so far out that it doesn't slow the starter. I have known new CDIs to alter the timing though. The slipping starter clutch is a common problem. If removing the plug lead doesn't alter things, it still can be a slipping clutch, or there is resistance on a thick wire (this includes earths) between battery and starter, check all connections.

[QUOTE=merryman;3508826]Take the plug cap off and leave the plug in. If the engine now spins faster, the spark timing is out, or the one way clutch for the starter is slipping. You can't alter the timing unless the flywheel has slipped on the crank but that usually puts timing so far out that it doesn't slow the starter. I have known new CDIs to alter the timing though. The slipping starter clutch is a common problem. If removing the plug lead doesn't alter things,


Thank you for the ideas. All the YouTube I watched I couldn't find anyone replacing the starter clutch on this style motor. Is it on the starter gear side of the motor and what exactly does it do? I think I could tackle replacing that.

This I haven't tried. Thank you

Never needed to work on a GY6 starter set up. GY6 was popular 20 years ago but seemed to fade away, and Honda clone engines took over. Looking at a parts diagram, the clutch sits between the starter and (I think) the crankshaft pulley. They only transmit power one way, so transmit the drive from starter motor to crankshaft but slip when the engine starts, so the starter stops turning when you take your finger off the start button.

What happened when you tried spinning it over without the plug lead on?

I hot wired the starter direct to an external battery to confirm the the wiring and ground was good. It still struggled to turn one revolution and it was pulling a lot of current from the test battery judging by the heat

Without the spark plug in it turns over fine, sounds like a strong battery like it should. That was through the ATVs electric. I took the valve covers off and turned the motor over and they seem to be moving up and down.

I'm stumped!

Bob

I will try one more time, "What happened when you tried spinning it over without the plug lead on?"

Sorry, I misunderstood. With plug in and plug lead off it will not turn over.

OK so it isn't an ignition timing issue. Make sure the battery is fully charged, new doesn't always mean fully charged, check those leads again, remove, clean and refit earths. If that doesn't make any difference, you may have a partial seizure. It is a lot easier for the starter to turn the engine without the plug but, with compression and a tight engine it may be too difficult to turn over. Other possibility is a faulty new starter or the starter clutch seizing. I had a Suzuki doing this and it was the bearing for the starter idler gear, yours doesn't have an idler, but the starter clutch does have a bearing.

Got it. Thanks for the leads. I found some other reading that points to the starter clutch so I'm going that route. Ordered the puller for the flywheel. It should be here today.

Thanks again

Bob

Are you sure it is on the flywheel side? Only going from a parts drawing but it looked like the starter clutch was driving the belt pulley. Also looked like it was behind the starter, so you would take starter out and poke the starter clutch out through the same hole.