Topic: Stuck Tensioner Arm - CB400F

[bassrocker]

Just to get some more minds in on this (since supersport and I have just been conversing); it seems I have a stuck cam chain tensioner arm (the U-shaped piece).

Has anyone had a similar problem on a 400F, and if so, what was the solution? I'd like to avoid tearing down completely and splitting the cases, so any insight would be good. If it's the only option, I'll bite the bullet and do it, but I'd like to keep on track towards finishing.

Thanks!

[BarryKelly]

Hey Bassrocker

I just finished putting in a tensioner on my 78 CB550K.  I'm not too sure how similar it is the the 400F, but I *think* that they are pretty close.  Basically what happened, is the spring that keeps the tension on the tensioner was gummed up, it wasn't smooth and was not putting enough tension on the chain so I had to put a new one in.

You don't have to split the crank-case to replace it, but you do need to take off the breather cover, the valve cover, the top of the head and maybe even the bottom of the head (you could probably do it with only replacing a head gasket and valve o-ring, but I replaced the base gasket aswell).  Once you get it apart, it's fairly easy to see how it goes in - especially if you have a service manual.  It took me about 10 hours to do it, but doing it a second time I could easily cut that time in half - it's not too hard, just it was new to me.

After running it last night about 30 km, so nice and quiet as the cam chain rattle was all gone, I'd say it was definately worth it.

Cheers

Barry

[BarryKelly]

Ahhh, I see how it works.  That's right, come to think of it in my clymers manual for the 550, it includes several models, one being the 400 and I see that's how the tensioner fits...

Well, I guess disregard my previous post!

Good luck!

Barry