Well when I try riding my 400ex it'll start cutting out at high speeds and at high rpm.. It backfires some too.. But sometimes ill crank it and ride all day and it won't give me any problem? But some days I ain't even get out of my yard and today it started to bogg down and not stay crank. I cleaned the carbs but I didn't do the best as in I ran out of things to clean it with.. But I put it back on and it crank and idled perfect? But if I ran it, it would cut out real bad.. Mabey it's the jets? It has a aftermarket exhaust on it and I know it's jetted but maybe there's something else to it? And if I ride for maybe 10 minutes I can feel the engine getting hott. I think it's getting way to hot than it needs to.. I'm open to any suggestions? I'm a newbie to this website.. And another thing is that the cylenoid has gave me problems since day one. The fuses wouldn't blow but wires would come loose and the terminals come loose very easily.. And something else is that the spark plug was bad.. I put a new one on there and ran it and it helped a lot but the next day it was the same? And the gap wasn't set and today when I set it, it made it worse? But the gaps in the right area.. .24 to .28 any ideas? I wanna check the timing...

 

Well it could be your cdi or it just might not be jetted right take it out and run the hell out of it for 20 miniuts pull your plug if it wight and burned its not getting enough fuel if its black its getting to much it should be a Carmel color hop I helped

 

Well I took the new plug out and it's just pure black.. It has a k&n filter and a custom cherry bomb exhaust.. The guy I got it from said its jetted but idk the sizes.. Should I rejet it? And what sizes? I don't know much about jetting a carb...

 

I would try that first being that's cheaper than other stuff but you said it doesent happen all the time so Mabey it's electrical my 400 had a problem last year I would hit it and it would just pop and cracked I wiggled a few wires that ran by the coil and it worked so I put a new harness on it and never had a problem since if you are going to reject it I would get a jet kit with a bunch of jets and to see what jet sizes they are look on the bitten they should say let me know if I helped at all lol

 

Well today it only crunk for like 5 seconds and that's with my hand over the air intake...