Coil

[bradje]

How can i check the coil on my 400ex?....what about stator?

also, the solenoid should have power coming out correct??...both wires show no power with a multimeter with the key on...maybe it only fires when the electric start is pushed in....either way this would not make it not spark right?

[aviator4]

If you're talking about the starter solenoid (the round tin at the front of the battery on a stock 400) then the answer is no, it won't have anything to do with the spark, unless it's sucking the battery dry.

The red wire going to the solenoid should have 12 volts to it at all times, since it's directly connected to the battery. The thick black cable goes to the starter and will have 12 volts when the start button is pushed.

If you're not getting spark, check the 15amp fuses. Make sure you've not popped one.

You can check the coil on the bike by pulling the spark plug wire, getting it close to a ground, and cranking the bike over, you should see a spark jump between the plug wire and the frame. If you have spark there, pull the plug. Chances are it's BLACK and may even be bridged with carbon.

[bradje]

thanks for the speedy reply...

i checked the fuses (i am looking for breaks in the metal correct?)
they seem ok...

i bought a new plug last evening and with it in the cap and against the engine or frame no spark....i guess you are saying to take the cap right off then hold the uncapped coil wire close to the frame and check it out??....if that produces no spark then i should assume the coil is bad or perhaps no power getting to the coil?

[aviator4]

Right you're looking for a break in the metal inside the blue plastic of the fuse.

If it's a brand new plug and you're not getting spark when you have it against the frame, then yes. I would say you're probably not getting power to the coil or CDI box. Have you recently changed the CDI out? It's a common mod to put a high-revving box in it. Has the bilke been submerged recently? What year is it?

[aviator4]

Just got off the phone with Don Blaylock at Little Sahara Power Sports. He's a 400ex guru. He says that chances are it's the rev box.

If you don't know what that is, is a small rectangular box mounted to the cross member just under the front plastics. Typically, they are housed in a rubber "boot". If you're not getting spark, chances are it's gone bad.

If you have a buddy with a 400, pull his off and plug it into yours. Chances are it'll fire right up.

[bradje]

thanks again....it is a 2003, stock rev box...not submerged or anything...i had it out the other day after a long winter...it seemed to run dry of gas....it was running ok and then i guess the spark just went away...

[aviator4]

Yep, thats how the rev boxes go. Either they work or they don't. There's really no explanation as to why they go bad. They are all solid-state.

Get an aftermarket box and get a little performance boost when you replace it.

[bradje]

does a 250r also have a rev box?....tell me again where it is please

[aviator4]

Yeah, the 250R has one as well I believe. I'm not terribly familiar with them.

On the 400EX it's underneath the front plastics right under the nose mounted to the frame on the right hand side (if you're sitting on it) it's tucked up under there.

[wilkin250r]

The 250r has one. In fact, I can't think of any quads that DON'T have one.

The rev box is a very crucial part to your ignition system. It's not just a rev limiter, but is actually your entire ignition timing system.

Your stator sends two different things to your rev box, a high power pulse and a low power pulse. The high power pulse is accepted and stored, and will eventuall become your actual spark energy. The low power pulse is just a signal, used as a trigger. Your rev box uses that low power pulse to calculate RPM, and know where the piston is located in the compression stroke. With this information, your rev box will know exactly when to fire the spark plug.