I have a 1971 CB500. Here's the problem in a nutshell. I start the bike, let it warm up, hop on and about a half mile down the road the engine bogs down and I lose power. Eventually the engine cuts off completely. I have to wait about 2 minute before I can start it again and then it happens all over again. I'm fairly new to motorcycle engines so try to bear with me. Any help? Thanks in advance.