Topic: Honda CM400 valve seal question

[Johnie]

I have a 1981 CM400 Custom I bought last summer with 1,300 miles on it and it obviously sat a lot.  It's a beautiful original bike that I put 1,500 miles on last summer.  The bike sat so much the valve seals are pretty dry and need replacing as it blows smoke on start up only after sitting.  The compression is good in both cylinders.  I was told I should be able to replace those valve seals by only removing the valve cover, cam, etc. and that I would not have to remove the head.  Does this sound do-able?
Thanks...

[mark]

If we were talking about an old Ford pickup, I'd say "yeah no problem go for it"...

I don't see it happening on the CM. I think the head needs to come off.


sorry

[Johnie]

Yah, it was an old bike mechanic that mentioned it.  I was not sure and have never dug that far into an engine before.  I have gone into V-8's and done valve jobs, but nothing that deep in a bike.  I sort of wanted to see what is involved before I try it.  I have the service manual but wanted to hear from the board experts. 
Thanks

[troppo]

use the old string trick...................
remove the battery (makes it idiot proof) take of the rocker cover and the spark plugs, i dont know the particulars of the bikes but i have done this with a car, push a heap of string into the cylinder and turn he crank over, when you cant turn it over you have enough string in there, that will hold the valve in place while you replace the seals
cheers mate
troppo

[crazypj]

In my experience the head has to come off (easy though as there are holes in the frame to allow for this)
 The cotters 'stick' to the valve after a long time just through normal spring pressure.
 Remove cam cover, back off rockers, undo the 8 long bolts on rocker/cam bearing mounts, (don't remember if there are 6 or 8mm bolts as well?) pull out tensioner blade and guide (not sure of exact sequence, haven't done one since around 1981~2)
PJ