VN750 is equipped with hydraulic lifters instead of push rods. Hydraulic lifters use a bubble of oil pressure to constantly push against the cam shaft, thereby eliminating any gap and manual adjustments. If they freeze or get sticky, then they could produce a lot of noise, and sitting out for 2 years probably didn’t help. If this is the case, then the noise will come from the very top of the cylinder. Luckily, a lifter is a lifter and the old one (if frozen) can be bored out and an oversized on inserted (this is what happened to my car).I have a 1999 750. I had the carbs off and cleaned. The plugs changed. It only has 26000 miles on it. I bought it from a guy that left it sitting out side for two years. ( what a dummy). Any ways i rescued it. Believe it or not It looks beautiful. I finally got it running. The day after I got it running. I jumped on it to take it to get inspected and It started to loose power and I i knocking so bad it sounds like it is throwing a rod. It is on the back cylinder. I have been reading in some other posts that it might be a cam chain loos. I will start up fine, but makes one hell of a racket. The cylinder is not dead but week. I don't know how to work on this thing but my friend does. But he has never worked on this type of V twin. He is used to the push rods. And this type of V twin does not have push rods does it?.
Any help world be appreciated
The other piece to check, and less expensive to fix, is the ACCT (cam chain tensioner). It too will produce a racket of noise that will come from the top of the cylinder, but slightly lower lifter. Search the forum for tricks, identification and repair since it is widely discussed.