Is there any way to tell if a CDI box is bad? I don't have the option of swapping out one short of buying a new or used one. My problem is that my '03 CRF450R won't start. I recently took the carb apart and cleaned it, put in new gas, new spark plug, changed the oil and put on a new air filter (all part of my spring start up). The last time I started it up was in September. I havent been able to start it however, so I checked the spark with a spark plug tester and it jumps at least a 1/4 inch- 1/2 inch gap. I checked all the wires and the coil for resistance, and they are all within spec. My compression is reading about 5kPa after about 10-12 kicks and the throttle open. My friend seems to think it's the CDI box, but after reading some posts, I'm leaning towards maybe bad valves. I bought the bike used 5 years ago and only ride trails in Ohio. I have never done a valve job on it. Should I buy a new or used CDI box or opt to send it to a mechanic who can do the valves? BTW, TT is such a great source for information on problems. I go to you guys whenever I have issues (brown nose alert!). Keep up the good work.