its either your valves or its knocking due to bad timing. both easily adjusted, probably just your valves. the valves are under the 10mm acorn nut cover on the rt side of your engine. take that cover off (oil will drool out a bit) and also remove the stud to easily access the valve adjustments. put your engine a tdc by slowly kicking over and waiting til the meter just flicks to 0. then check your pushrods by trying to move them up and down or from side to side. if there is any movement, then they are too loose. they should spin freely with the flick of a finger but should not move up and down. the exhaust side should be a bit looser. I'll try to explain how to adjust the rods, but to be honest, I didn't understand how to do it until I actually got my hands dirty... you'll need two 13mm open ended box wrenches and a 10mm one as well. Back off the 10mm nut, adjust tightness of the valve then retighten the 10mm nut which holds everything in place. Its a tight fit to get the wrenches in there, some grind down the sides of their wrenches to fit better.
hope that helps, good luck!