i have a 87 yamaha warrior 350 stock .it clunks when i start it and also when it shuts off. it doesnt do it every time. can anyone tell me what it could be.

 

It's the one way bearing, also known as the starter clutch. Usually they get messed up because of people trailering them in gear and pop-starting them. Sometimes they'll only last a couple months when they start making noise like that, sometimes they'll outlast the rest of the bike. So you could either play it safe and replace it now (about a $200 repair if you do it yourself) or you can just chance it and hopefully it'll hold up.

What I did with mine when it started clunking, is that I just rode it until the noise started getting worse. When the clunking and knocking started to get harsh I replaced it, because once they get that bad they start setting metal chips free into your oil, and you don't want those getting stuck in any of your bearings.