I traded for a 01 400EX couple of weeks ago, It has been starting fine. You could just hit the starter button and it would fire right off, no choke needed. Last weekend it set outside till late and it was fairly cool, down in the 40's. I went to start it and it would not fire. I tried choking, but still no start. We ended up pulling it and it fire right off, then it would start every time again. On Sunday I checked and adjusted the valves, they were off some, but not much. It would not start again and I pushed it and it fired right up, then no more problems. I started it off and on several times during this last week with no problems. Yesterday, it would not start again. I pulled it off and it started right up again and started fine for next several hours. Then after it set for hr or so, it would not start. I have my buddies 02 400EX so I started changing parts. I tried another coil and CDI box, but it made no difference. I pulled the plug and check and I was getting no fire. However, all I had to do was push it down the driveway and it started right up. The guy I traded with had been racing the quad and he had taken off all the switches. It just had a starter button and a tether kill switch. He had the plug jumpered so there was no key. I replace the key and will replace the starter switch with the factory one. Could jumping the switch maybe have done some damage to the electrical system? Any other suggestions as were to look for the problem?

 

Well im no expert , but if you got the quad from someone who raced it,they may of put in an after market rev limiter. If this is the case it will cause it to do that. mine did. Im pretty sure its a fact with an after market rev limiter they start rough. My quad ran fine but sometimes in cold weather need to be popped started. I wouldnt say its electrical if the quad runs fine after started.

 

I exchanged the CDI Box with a 02 400EX that I know is stock, it made no difference. When it pulls this stunt I have no fire to the plug at all, yet when I push or pull it, it starts right up.

 

If your 400ex is a battery CDI ignition (and I'm pretty sure it is), I've noticed on Honda's if your battery is discharged, they don't start very good. Sometimes not sparking when the engine is turning but letting out a fat one when you let off the starter button. I think the starter drops the battery voltage enough so there isn't enough power left to operate the ignition system.

 

Its a brand new battery. I had to buy one for my daughters 300EX, so I put the new one on the 400 and the used one on the 300.

 

REX,

What does the plug look like? Is it black and sooty? If it is, get a new plug and try it. It really doesn't help to clean it. The 400EXs are notoriously hard starters.

 

I have tried a new plug, no difference. When its starting right, it will start right up, no choke, no throttle, just hit the button and it starts almost instantly, even when cold. When it does its thing, nothing works. Leaving it sit overnight does not work, but soon as you pull or push it starts right up. Then it works for a while. Very frustrating.

 

Just talked to a mechanic at the dealership were my son works. He said it was a bad stator or exiter coil. I will check them with an ohm meter tonight and see which one is giving the problem.

 

Checked the specs on the stator and it was way out. I ordered a stator from Ricky Stator, came in today, started right up. When changing over the plug on the stator I noticed one of the wires looked to have been hot and it was stuck in the plug. I figure this was prolly the problem. The new stator from Ricky Stator puts out 200Watts, so I will be able to add some trick lights to the quad now.

 

I recently took my mom's boyfriends 400ex through a big mud hole and got it stuck.
While i tried to get it out it was spinning and rocking, it kept stalling so i got off and
i tried to pull it out but got no where so when i got back on it wouldnt start it had
to of been electrical because i can coast start it. i tried to let it sit but it still wont start.
when you push the button it doesnt make a sound. If anyone has an idea of how to fix
it please let me know.
Thank you
250xryder1