my friends YZ chain is rusting he uses WD-40 for a lube does he need a new chain?
its rusting on the bars were the sprocket hits the chain(the bar things)is this normal?

 

If its still within the deflection range and moves freely after a good soak in your choice of oil, I think it will be OK. Not so sure about the wd/40 though. I don't think it would hold up long enough under pressure unless someone can explain to me different. I would assume its a non o/ring chain. That makes it even more important to have a good chain lube on it other than wd/40. I use Honda HP chain lubricant on my non o/ring chain on my KDX 200. Chet

 

He should use Maxima Chain Wax. WD-40 doesn't stay on the chain very long, it just flies off. The Chain Wax is very sticky and stays on the chain.

 

I use Bel-Ray chain lube, and blue label PJ-1. PJ-1 is a GREAT chain lube. About WD-40, on an O-Ring chain, WD-40 is a great lube. WD soaks into the rings, and lets the rings soak it up, and hold it. However, he SHOULD get another kind of lube to put on top of it. Go over the chain w/WD-40, then come back with PJ-1 or a different brand. I highly recommend PJ-1. They make quality products, and they work very well.