knock

So I have the option to get a 1980 Yamaha Midnight Special, and I've talked the guy down from 600 to 475. The only issue is the fact that the buyer states that when it idles, it runs fine, but when you open the throttle, it has a knock in the engine. This would be my first bike, and I wouldn't...

Hi there! I installed some shorter rear shocks on my Honda cb900. The shocks compress just fine, but on the extension they 'top out' and bang pretty hard. Anyone have any ideas how to stop this? I am assuming the shocks are oil filled...could a low oil level be the problem?? Thanks so much...