sputtering in higher rpms, please help.

[glatf70gg]

During my last ride at trevorton, my 400 started to act weird at the top of each gear. It acts like I'm letting off the gas and hitting it again and again. Check plug, was running way rich.170 main jet with foam filter, no lid, and a slip-on. Changed plug and main to 155, its little better but still doing it. Bike ran great before the last ride. Thanks for u guys help.

[honda400ex2003]

it might be worth checking the compression on, and further checking the jetting. that would be the 2 things i did first anyway. I would say that a 155-158 would be perfect for your application at around 1500 ft above sea level give or take. steve

[glatf70gg]

I changed the cdi box, still doing it. Seem like maybe rev limiter, thinking clutch is slipping at higher rpms. Gonna check clutch this week.