Topic: cb400f checking cam chain tension and guides

[honda cb400f]

Hi, Just wondering about cam chain noise on my 1976 cb400f.  Im fairly certain that my my auto adjusting mechinism isnt working becuase i have made a mark on the slider bolt that is held in at the front of the engine with the adjuster bolt and it doesnt seem to move when i take it out and look down the hole whether the engine is idling or stopped. i have tryed to removed the blanking bolt above the slidder bolt and give it a hand with a screwdriver down the hole. anyway i have heard of a way (http://www.sohc4.net/?p=3095) that you can take the head cover off and loosen the 2 bolts that hold the top of the bow by about 5mm and see if the mechinism pushs the bow up into the dampener then lock off the adjuster then screw down the bolts and put it all together and test. has anyone tried this technique? and is there a way of feeling the cam chain tension or gauging if your even in the ball park with the cylinder head cover off.
 and if i have a loose cam chain im afriad that the chain guide might to worn out. how do you remove them to inspect? is it a matter of removing the 2 afore mentioned bolts behind the cam chain sproket and slidding it out as it looks like on the exploded drawing or what.
any help would be greatly apprechiated as i dont like the amount of noise at the moment and it seems to disappear over 2000rpm which i hear is cam chain noise.
thanks in advance

[MoMo]

How many miles on the bike? Some cam chain noise will be normal...Larry

[Psychonaut]

H i have tryed to removed the blanking bolt above the slidder bolt and give it a hand with a screwdriver down the hole.

Did you do this with the engine running and the lower set bolt loose? Did it stop the noise? This is how I adjusted mine. It only took a little pressure with a bent coat hanger.

[jessezm]

If, while your engine is running, you push down on the rod and the camchain noise does not quiet, you could have a seized pivot on your tensioner arm.  But before you determine this, make sure that the excessive noise isn't from your Carbs being out of sync.  This can also make a lot of noise at idle.  Also, you really have to work hard to feel any movement at all in that rod, so if you don't feel or see it move, that doesn't necessarily mean it's seized.

I'm interested to see how many miles are on your bike, but most of these 400's have some sort of damage to the pivot area of the tensioner arm.  What happens is that there is very little clearance, and if the camchain is loose at all, it can start eating into the pivot, and before long, this seizes the pivot into place so it can no longer work like a hinge.

Refer to this page:http://www.capitolcycle.com/fiche_section_detail.asp?section=121734&category=MOTORCYCLES&make=HONDA&year=1977&fveh=2913
In order to see if it's working you can take your valve cover off and pull out the  slipper (, being careful not to loose the damper (4),  then push down with a flathead screwdriver where the bottom of the slipper was nestled.  This should move smoothly with a bit of force, and spring back.  If you take the guide out as well (10), you may be able to look down there with a flashlight to see if the pivot is chewed up (you'll see two "track" marks ground into it by the chain).  But the chain itself might block your view (I don't remember, since I looked at mine with the cam and sprocket out).

If you determine it's fully seized, then you probably wont be able to adjust it at all.  I have seen where people have replaced the oil check bolt (11) with a longer bolt that is smoothed out into a rod at the end with the threads removed.  This can be tightened to mechanically press down on the rod, but you risk both overtightening the camchain as well as stripping out those tender threads...

Unfortunately, if the tensioner arm's pivot is totally seized, you can only get to it by digging into the cases, as it's bolted to the underside of the upper case I think.  I believe somebody makes an improved billet replacement for the part.   Let us know what you find!