Why does my 2001 honda 400ex cut out on top end?

 

Your main jet my be clogged a bit or even to small

 

thank you but I cleaned the carburetor thought it was timing but I'm pretty sure its the cdi box

 

need more info....have you changed anything? smaller rear tires, opened up the air box, or added a pipe/muffler? have you changed the front or back sprocket to a different size? Honda has a pretty low rev limit, if you open up the air box, or pipe it, or drop the gearing or tire size, anything that lets it rev more or easier, you will bounce off the limit, and it will cut out and surge on the top end. I had to put a +1000 rpm cdi on both my sons hondas, his 300ex and 400ex, when the intake and exhaust was opened up, revved so much better, but was constantly hitting the limit.