Tapping on the top of the engine
3 Answers
Diagnosing noises is impossible on the net. You should have someone look at it before it blows up as this could be serious.
Usually a horizontally-opposed four taps in in 4/4 time. Interesting that you have a "two tap." "Two-steps" were wildly popular song and dance form a century ago, so find a partner and enjoy your time while awaiting the bad news re a bent valve or, more likely, internal rod bearing wear. 2004? Time to toss it.