My son was recently riding our 05 TRX450R and it shut off on him. According to him he was maybe 3/4 throttle when it seemed to loose power and eventually stall. No oil showing an it seems to have all its compression so... next thing I checked was for fire by removing the plug wire and using a screw driver next to a.block bolt. No spark. My question is... where do I start my troubleshooting? Are there common issues?