Idles then stalls out?

[tokarev]

Having a problem on my sons Xmotos 250cc - You can start the engine it seems to idle OK , even rev the engine a few times and it will go back to idle. Then you decide to ride the bike - you go a very short distance it starts to cut out and stumble then quits. Theres no water in the fuel ,no obstructions in the fuel lines, it almost seems like a ignition / wiring issue.
Has anyone had similar issues? I had to replace a couple of the ground wires near the battery over the weekend but it had this problem before then. Any suggestions on a starting point? Thanks

[Weldangrind]

When was the last time you installed a new NGK? They're cheap and easy.

[tokarev]

You know thats the only thing I havent messed with yet - next on the list for sure. I also have a M274 Mule that was running on 1 cylinder (has 2) and that turned out to be a bad plug too. His bike was running fine back mid summer then it sat till a couple weeks back.

[Weldangrind]

Since you said that, is it full of old fuel? Maybe dump it out and refill with fresh stuff, along with a new NGK.

[tokarev]

All the fuel was drained - carb removed to check for crud (none) - will be swapping out the plug to see if it helps.

[katoranger]

Tank venting?

[tokarev]

Today I tried to fire up the misfit bike swapping out the spark plug - no spark at all - both plugs work fine in my other bike. Aside from a wiring/connection problem whats the most common part to fail on these bikes?

[FastDoc]

First things first. Is there spark and fuel flow? Compression?

[Weldangrind]

You're saying no spark at all with known good spark plugs, so I'd zero in on kill switches and safety switches. Does it have a switch that requires a brake to be applied before it will start?

Test the kill switches for continuity. That's free.

[katoranger]

Then next would be probably be the CDI. You could try swapping them between the bikes.

[tokarev]

Didnt get a chance to mess with it today but it has plenty of fuel, compression just missing the spark park. Might swap out the cdi with the working bike first just to see what happens.

[FastDoc]

Good news. The complicated/expensive things are not the problem.

As a general rule, on a Hondoid Chinabike, no spark is the CDI until proven otherwise. :?

[tokarev]

I sure hope so on the CDI - an easy fix would be great. Still going to give all the wiring a good look see.

[tokarev]

How does one explain having no spark one day and having normal spark a couple days later? Well thats what happened - I tried starting the bike on Friday and it fired right up. I let it run for a few minutes waiting for it to stop running and it didnt. I rode it around my shop waiting for it to stall out and it didnt. I did find a bad connection on the negetive side of the battery (soldered it). Question - The spark is independent of the battery state of charge? would the faulity ground connection on the battery prevent spark?

[FastDoc]

From what we've seen here CDI's tend to fail intermittantly at times, then altogrther.

A faulty ground is also a pretty common issue.

[Weldangrind]

I agree with Doc's CDI assessment.

Also, if the charging system is marginal, I can see where a bad ground would give you trouble. I had rust inside the flywheel on one of our quads, so I lightly sanded it and coated it with some light spray lube (and wiped off the excess) to prevent future rust. I'm not sure if it helped because I was chasing down another problem, but it can't hurt.

You could still have a kill switch problem. Next time you start the bike, wiggle the harness around each kill switch and see if it will fail. You can also try tapping the CDI to see if it will make the bike stall.