Well, i dont mean the HotCams set is ruining something because i still believe that i have just a tuning problem. I installed a set of these cams a few weeks ago together with a Wiseco high compression piston. I took the bike for a spin on the pavement and noticed a slightly engine failure wich i posted the story here in this fórum, for some of you who might remember. I had to store the bike again after that short spin due to the lack of time to ride it. Anyway, this Sunday i started the bike (allways starts easely) and prepared myself for an off-road ride. I left home alone heading for the dirt tracks and was riding only with 1/4 throtlle to let the engine warm-up. When i decided to open the rest of the throtlle the engine started to fail and also backfired constantly...looked like when we are running out of gas. This happened at 1/2 throtlle and didnt let the engine to achieve higher revs. Also, the engine now makes a lot of valve noise at medium revs, doenst make this noise at low or high revs. I decided it was better for me to head home but suddenly the engine went OK. It was very strong in low end and i even noticed the wild top end power out of the 426cc but the valve noise was still there. I kept my riding plans untill i stopped the bike to drink some water and to cool down a bit. The engine was off for like 15 minutes. When i started it again, easely i must say and with stock idlle, it made the same thing again...didnt wanted to go over the 6.000rpm(aprox.) mark. Started to backfire and loosing power but allways with perfect idlle capabilities, never shuting off. This problem again went away after 1 or 2 minutes rirding, then everything looked OK again. The cams are aligned like the factory set and i didnt modify the HotCams cam gear geometry. The valve lash is tuned with the same settings as the original lash would be but the valve noise coming from the head area makes me think something is wrong. I e-mailed HotCams but still waiting for the answer. There is a member here wich has the nick "HotCams", dont know if he has nothing to do with the HC guys. I just wrote this stuff hopping for some opinions of someone that might experienced anything similar to this. Thanks for your time.