So I had my 400ex out and I was riding for about 2 hours. I came up to our campsite and i was idling letting the bike cool down. I cut it off, and my buddy wanted me to show him how to ride again. It had been a while so he wanted me to show him how to use the clutch properly and everything. So long story short, he sits on the bike I grabbed the clutch and pulled it in, pressed the start button and she started right up. About 3-5 seconds later, you hear a click and the bike just cuts off. It had only been sitting there idling in neutral. After that the bike had no power. No click, no neutral light, no headlights. I couldn’t jump the solenoid either, I tried right after it wouldn’t work with the push button. No sparks, nothing. So I pushed it down a hill and bump started it. It started no problem. I rode her home and I took the battery off and put it on a charger. The battery charger immediately said the battery was dead. So I ordered a new one, it’s a size to small but it still works. I put it on the bike and tried to start it and still nothing. No lights, or anything. But now it will let me jump the solenoids. The poles spark when crossed, but now the starter makes a weird whirring sound. That makes me think the starter is bad, but why would the bike just cut off if the starter was bad? Is it making that sound because it’s not getting enough power from the battery since it’s a little smaller? It is 12volts so I don’t see that being the issue. Any thoughts? Here’s a video

https://youtube.com/shorts/i_yXZTbnthY?feature=share

 

Can't tell from the video, but most likely thing is your new battery is on the wrong way round. This will instantly blow the main fuse, hence no electrics, and make the starter motor spin backwards, so it will just slip the one way clutch in the starter mechanism. Even if the + side is to the red wire, double check with a meter that the battery + is really pos, as it could have been wrongly charged by the supplier. Once you get things right, check the bike is charging and not "leaking current" as something killed your old battery. Also putting a battery on the wrong way can kill the regulator before the fuse blows.

 

Well the new battery I originally got was to small and that’s why it would not crank over. I’ve replaced with a good battery and now I can jump the solenoid to get it running and cut it off with the kill switch but the electric start does not work. Any suggestions on getting that damn button to work?

 

Have you checked the main fuse? Make sure the ignition switch is OK. If it isn't those, check pos and neg thin wires at solenoid with a 12v test lamp, if there is a circuit when you press start button faulty solenoid. If not, somewhere there is either a faulty switch or wire in this circuit. Trace whichever wire is dead, back until you find the fault.