hey guys i have a VERY strange problem i have seen a few times while riding my XR recently. first i should list the upgrades on my bike pro circuit T-4 exhaust, K+N filter and rejetted carb. i dont remember the exact size of main jet i installed but i belive it was slightly richer than stock. i am at 6500 feet and the upgrades left it running lean. recently i have noticed that under some special circumstances my bike will flat out quit on me. as in loose all power like someone pulled the plug wire off the engine. in every case i was either shifting or had just shifted to the next gear. to me it seemed like maybe i ran the float bowl dry because when i let off the throttle and back on again it seemed to pick up and run fine again, abeit a few backfire pops then im back in business again. i thought perhaps my filter having not been cleaned may be the culprit and maybe running wide open was running rich enough to suck all the gas out of the carb before the tank could refill it. so i cleaned that and figured my problem was gone. yesterday i was riding in the mountians and not really pushing the engine that hard and as i shifted i belive i may have missed a gear or shifted between gears. i couldnt really tell because the engine has just started coasting down, no pops, no bangs, no nothng it was like i was holding the kill switch. i cant be certain if i heard what i thought but it made a sound that made me think a valve was held open. if i had to guess it would be exhaust because there was no back fire in the carb or the exhaust. it very well could have been my imagination as i have never actually heard the engine in a high rpm coasting down situation and it may have been normal engine coasting sounds with out the exhaust popping so loud i cant hear the engine running anyway. but after i grabbed the clutch and down shifted again and let the clutch out again it seemed to roar back to life no problem. i then found a stretch of straight road and did a couple more sprints and upshifted each time it seemed to be about max rpm and no problems. this issue seems to come and go. i cant tell if it has somthing to do with the terrain i am riding on or not. i began to wonder if maybe the bumps on the road was shaking the carb enough to cause the float bowl not to fill completely or somthing. the only reason i suspect this is because on paved roads i can throttle it all day long and no problems. i even had some punk kid in a 89 prelude 2.0 SI try to race me from a light on my way home and with a full throttle start and holding the throttle wide open and speed shifting the clutch and gears all the way to about 70 mph in 6th gear i had no problems. (he lost BTW) every tme this has happend i have been under full throttle and on a bumpy surface. every time it has been while changing gears or going through gears on a rapid acceleration run. after the last time (yesterday) it happend 2 times. it was hard to tell when i lost power if i was between gears and maybe let the clutch out too soon. i just dont know, when it happens i try to down shift and that seems to resolve the problem and it runs fine. i have no idle problems, no hesitation, no rough running nothing.. otherwise the bike runs perfect every time. the bike has about 600 miles on it and i bought it new. is there any way i could be accidently hitting the rev limiter? if you hit it does the engine cut out for a few seconds? in a car it just wont go any faster. i dont know if bikes are any different. is there some sensor that detects you hitting neutral or between gears to cut the motor? is there any way i could be floating my valves? (i would assume that would distroy the engine) i seriously dont think i could have pulled the decompression lever as i have it positioned down and have to reach to grab it. i just dont get it, what could i be missing?