It would probably be your coils there in your cdi box they look like two black little cylinders
first check your spark plug then test your ignition coil if these are good then it is probably the cdi but there is no way to test a cdi box.
the only way to test a cdi is to repalce it. There is no other diagnostic for a cdi box
take the cdi box off and try cranking the scooter youll notice that it still sounds like the coil is bad then wait till night time plug the cdi back up then watch the coil if it throws a spark its not your cdi it might be your spark plug but if you see no spark then its most likley your cdi box or coil thats teh best way to know if your scooter is cdi enabled or needs a coil theres a big defrence when it comes to price of these devices though.
Sorry you can't rebuild a CDI box, as a matter of fact you really can't even diagnose it as bad (usually, a few rare bikes have the ability to be tested), you just have to rule out everything else first. Considering Just how much a CDI box costs you DEFINITELY want to confirm that everything else is ok first. The only other way to check the CDI is if you have a friend with THE EXACT SAME BIKE! Try and talk them in to swaping with you, just to see if it'll run. However if there is something on your bike causing the CDI to go bad, be prepared to buy both of you a new CDI. Good Luck.
One way to check the CDI on an alternator is to use an ohmmeter. If you do not know how to use an ohmmeter, you may be better off by taking your vehicle to a repair shop to look at the alternator.
They don't have fuses! I found that out the hard way!
Normally, they don't start to go bad. They either die outright or have moments where they'll just work or not but doesn't last long that way. But be sure to test the output of the pulse coil and the kill switch before condemning the CDI box.
Ah, the CDI box on a Yamaha Big Bear 350 is usually located near the battery or under the seat. It's a vital part of the ignition system that helps your ATV run smoothly. Just take your time to locate it, and remember, there are no mistakes, just happy little discoveries along the way.
CDI BOX OR STATOR jsstang87, Also look at your ignition coil! Make sure your key way hasn't sheered off, make sure all your wiring is ok
there is really only one way to test your cdi and that is swapping it with one that you know works and trying it.
There is no oil to be checked, it's a 2 cycle so the system gets it's lube that way.