I just recently finished a total rebuild of my 86 310r and im already running into problems. When i first got the quad last fall i was having problems with it feeling like it was hitting a rev limiter about mid rpm and it wouldnt rev out fully. I figured i would worry about it after i got done rebuilding it if it was still doing it. After i got the motor broke in and i went for its first ride it was still doing the same thing. So i pulled the cdi box off ( a red one ) and stuck it on my buddies 250r and it made it do the same thing mine was doing, bad cdi box right? So i ordered a new one and when it got here i put it on my bike and it ran worse than before, cutting out bad after about 1/4 throttle. So i put the new one on my buddies bike and it done the same thing again. My buddies bike was kind of cutting out in high rpms before we started swapping cdi boxes around so i figured i would try his cdi box on my quad and ill be damned if it didnt make my bike do the same thing. 3 cdi boxes, ( one red and 2 black ) one of them bran new and all of them are bad. What is the deal with junk cdi boxes? Does anybody have a good cdi box they would part with or know where i can buy a good one? This is really frustrating.