questions about cam chain tensioner... I think mine failed

[pimpazzberetta]

Was out riding today and suddenly heard this terrible clanking/slapping sound coming from the engine. Pulled the cam cover off and noticed there was a bit of slack in the timing chain, so I moved the cam, and heard the slapping sound. Looked deeper and noticed that the chain guide was slapping back and forth between the chain and the cylinder path cut out for the chain. Removed the cam chain tensioner and the piston is compressed fully into the body. So I think the tensioner is bad or somehow lost it's abilty to push the chain guide.

I have no idea how to tell if it's bad or how to reset it if it's not. Why did this happen?

[400exracer511]

It should be pushed all the way out.... when you twist the thing in the center with a flat screwdriver it should come in as you twist. Then let it go and it should snap back out real fast. Sorry that is the best I can explain it. It sounds to me like you need a new one. As for why it happened, you are unlucky.

[kwik02gixxer]

that happened to me when i rebuilt my 426 sounded bad so i shut it off pulled it home and checked it out my tensioner and it was in all the ways not out put a new one on and all is fine now. later kellie

[400exrider707]

They are supposed to be changed when the cam chain is changed as a rule of thumb, though hardly anyone does it. I believe in the Honda manual it says every 100 hours, which might seem like a lot but Im sure there are 400ex's out there with many more hours than that. I would definitely get a new one, yours is toast.