Hi all. I just recently rebuilt the top end on my 2000 XR650L. It was run low on oil and trashed the cam journal. I sent it to XRs only and they remachined the journal and did a valve job. I installed the new head and put it all back together. I put a HotCams stage 1 cam in it. Bike fired right up and idles ok. When I rev it and let off though, it backfires and it looks like there is smoke coming from the engine! Any help or suggestions would be great, I just want to get this thing running so I can sell it and get a KLR. I'm done with this thing!