That tapping could be the valve lash set too loose - check valve lash with feeler gauges , or cam chain or chains stretched - pull cam chain tensioners to check how far out the tensioners are, could be chain guides are worn, could be the primary clutch weights are worn making a similar noise to tapping valves. There are a lot of posts on this site and you tube on how to check all this stuff, and the service manual as well - it is not too hard if you have some engine background, tools, and can follow directions well.
05 750,Stock Engine,Muzzy Pro Exhaust, Uni Air Filter,
14" Vision Bruiser wheels, 26" Kenda Bear Claw HTR,
3" PVC Intake w/restriction - 2" ABS CVT, center snorkels,Carbs Keihin-#40 pilots 2 1/2 turns out A/F ,#158/#158 mains w/30 thous. washers under stock NFKL needles, 2012 front suspension,
Mr. Gasket 42s Fuel Pump Mod
10" Hayden s-type Electric Rad Fan Mod - mod fan mount
Aftermarket ebay radiator