I would think it is a carb problem. It sounds to me like your pilot jet is too small. How does the bike idle? Is it an automatic or manual shift? Heres a way to check the cdi and coil.
https://itstillruns.com/test-atv-ignition-pickup-coils-7948208.html

 

Make sure diaphragm in carb is seated properly and not ripped at all and all jets and passages are clean.

 

Thanks for the fast reply I've made my first YouTube video just for you guys it was hard to hold the phone while driving sorry for the bad filming lol !! so tell me what you think thanks

https://youtu.be/7qDVE3umPcI

 

X2^^^^ and make sure you didn't mix up the jets as they look identical.

Sent from my SM-G950W using Tapatalk

 

The carburetor diaphragm is not cracked and it sit to is place properly
thanks

 

I'm gonna remove the carb again !!! make sure I didn't mess up with the jet primary is 150 secondary is 75 and I dont remember the pilot jet # a gonna find out and let you know thanks

 

Based off the video I do believe it is running lean (not enough gas). On the carburetor there is a screw on the bottom near where it goes in the engine that can be adjusted. My 02 400 recommends to have it 2-2.5 turns out to assist with the tuning.

 

Hi thanks again for helping me !! the jets are not mess up 150 main 75 secondary and 38 for pilot jet the air screw have been adjust 2.5 turn out Maybe a blocked passage in the carburetor?? I'm confused

 

Jets are correct. Service manual says 2 1/8 turns out but you’re close. Choke/enrichener is not stuck closed is it? Does it cold start without choke? If it does it’s stuck closed. Timing is good and valves set to spec???

 

It seems as the pilot jet may be too small. I think the stock is the 38, but I am running a 40 in mine. Maybe try bumping that up. I think my main is 140. Just keep in mind yours is one year older than mine.

 

FYI, not even the same motor. Yours is a water cooled 400. OP’s is a 400 air/oil cooled 376cc motor. His jets are correct!

 

X2.....^^^^^

 

Just making a recommendation. My stock pilot is supposed to be a #38 (p/n 5507-246 same as 03 btw), but I have found the 40 to run better.

 

I have the same rig with almost the same story. Reviving it now after a few years in the back of the garage.
I replaced the flywheel, stator and pickup coil from rmstator, based on enough stories about the magnets coming loose and making a mess. Decided it was not “if” they came loose, but “when”. I’m still reassembling so haven’t started it yet, but I had similar sounding symptoms as yours.
Troubleshooting before ordering all the parts led me to very low resistance on the pickup coil. Should be 200 ohms and mine read 40 ohms.
Greg

 

Sorry for the late reply I did not have time to put on the bike... and don't want to ... spend to much already!! I'm scared that's have something to with the pickup coil like Greg say I replace the flywheel only thinking the rest was fine cause it showed no signs of damage I'm gonna check that this weekend and let you know and again thanks for your help!!

 

The pickup coil can be changed without changing the flywheel and can be tested without pulling the case. Follow the leads out of the top of the case to the connector under the seat. Measure resistance between blue and green leads - should be 200 ohms +/- 20%.
Like I said - my magnets were still solidly glued down and ok but I didn’t want to risk them coming apart out and I believed there is a strong chance they will. Your risk tolerance may be higher but this going to be my wife’s bike and she has no tolerance for breakdowns and field maintenance.

 

I've checked between blue and green wires and I got around 196 ohm so I'm thinking something is wrong with the carb
Thanks for your help!!

 

Finally the bike is WORKING GOOD the problem was the carb!! would you believe I ending up buying a brand new Chinese replica Carburetor on Amazon for a big 65$ shipped to my house I wasn't expecting nothing from that carb but guess what?? It start to run good again it was a perfect fit !! So now next time I have carb problem I guess I'm gonna change the carb instead of rebuilt it 65 dollars some rebuilt kit cost more than that !! Now I need some brake master cylinder is stuck and foot brake dont work ether but at least I got the bike running again!!!
thank you so much for your help !!

 

Good to hear you got it running [emoji106]

 

I’m pulling and cleaning my carb one more time and if that doesn’t work, I’m going to do a new carb as well. Do you have the amazon link to the carb you got?

Edit - carb was so varnished up that I ordered a replacement from amazon. The old one will go on my “someday” pile ... someday I’ll tear it down and throw it in the ultrasonic cleaner ...