Topic: Replace tach drive seal??

[KC_Northstar]

The valve cover on my CB750 K2 had a crack in it, so I bought one off Ebay.   I'm about to have the new one polished
and am wondering if I should replace the tach drive seal.  So my question is are the seals easy to get out?  How
much of a problem are oil leaks from the tach drive?  I would hate to put my engine back into the frame only to
find out I have a oil leak at the tach drive.

KC

[Gordon]

An oil leak from the tach drive seal is not a big problem, aside from having to clean up the front of the engine and possibly your pants.  Replacing it is not very difficult and does not require removing the valve cover, only the tach drive housing.  Whether or not you replace it as a precautionary measure is up to you.  If it were me, I would probably go ahead and do it since it's cheap and will need to be done eventually anyway, but, like I said, it's not a big deal if it needs to be replaced later on, either.   

[KC_Northstar]

"Replacing it is not very difficult and does not require removing the valve cover, only the tach drive housing"

What the heck is a tach drive housing?   I don't see any way to replace that seal without removing the valve cover.
The valve cover on a CB750K is all one piece and the seal is pressed into it from the inside.

KC

[Gordon]

Sorry about that.  I was in "550" mode.  There is no tach drive housing on the 750 valve cover, as you stated, but the oil seal still goes in from the outside, so valve cover removal is not necessary.  You will either need to use a pick or a screw to pull the seal out.  Be careful not to damage the sealing surface.  This goes for whether you're doing it with the engine installed in the frame or not. 

[KC_Northstar]

OK, Just took another look and yes it goes in from the outside.  Good to know I wouldn't have to remove the valve cover
if it needed to be replaced in the future.  My valve cover is currently off the engine, so I guess it only makes sense to
replace it.  Any tips on pressing the new one in?

[MCRider]

Not a press fit in, just unscrew the holding screw and use a small flat tip screwdriver and fish the old one out. Just drop the new one in da hole and hold it in place with the screw.

I believe the new one will require some encouragement to find home, though it will be easy. IIRC a deepwell 10mm socket will do the trick. Or something similar.

[Jiminy Indy]

But from past experience if you already have the cover off it's a whole lot easier to push the gasket out from the inside than to try and pry it out later. Also make sure you have the correct side facing out on the new one.

[Gordon]

Not a press fit in, just unscrew the holding screw and use a small flat tip screwdriver and fish the old one out. Just drop the new one in da hole and hold it in place with the screw.

I believe the new one will require some encouragement to find home, though it will be easy. IIRC a deepwell 10mm socket will do the trick. Or something similar.

+1

I use a standard length 10mm socket with an extension to seat the new seal.  The screw is only for holding the tach cable in place.

[MCRider]

But from past experience if you already have the cover off it's a whole lot easier to push the gasket out from the inside than to try and pry it out later. Also make sure you have the correct side facing out on the new one.

Certainly it would be easier if the cover is off, but can you push the seal from the inside? You'd have to remove the gear drive at least, but I'm not sure if that even gives you a place to push.

The actual method for removing the seal when the cover is installed is not to pry. Rather, one drills a tiny hole in the fleshy part, and another 180d out, thread 2 small screws in and pull. Easy peazy.

[KC_Northstar]

Ok, So I just went out to the garage and removed the old one.  Seeing as my valve cover is off I removed the gear and then
pushed the seal out from the inside with a small screw driver.  Then I reinstalled it, just to see how easy it will be with the
new one (which I do not have yet)   If you try to install it without the gear, it has a tendency to flip over.  I reinstalled the gear
and the gear shaft keeps it from flipping.  I pressed it in with a deep well socket.  Pretty easy.   I actually feel a bit stupid
for not figuring this out myself. Thanks for the responses guys.

KC

[bjatwood]

I Love this site!
You post some backyard, driveway advice, to a fellow owner and somebody will always respond with the Clymer/Honda technical jargon like you must use a bla bla blaaaaa, and then cut the gasket with a surgical scaple at the 9 o'Clock position just through the outer cortex not to harm the valve cover but to....................

[MCRider]

I Love this site!
You post some backyard, driveway advice, to a fellow owner and somebody will always respond with the Clymer/Honda technical jargon like you must use a bla bla blaaaaa, and then cut the gasket with a surgical scaple at the 9 o'Clock position just through the outer cortex not to harm the valve cover but to....................

I think in this case the "Clymer/Honda technical jargon" goes something like: "remove the seal".

Anything beyond that is just what's worked best for someone who's actually done it.         

[bwaller]

The scoop is to replace the seal with one from a DOHC model, it's 1mm thicker I believe. Often the original seal doesn't fit snug enough and oil will seep past it.

[Gordon]

I Love this site!
You post some backyard, driveway advice, to a fellow owner and somebody will always respond with the Clymer/Honda technical jargon like you must use a bla bla blaaaaa, and then cut the gasket with a surgical scaple at the 9 o'Clock position just through the outer cortex not to harm the valve cover but to....................

In this particular case the backyard, driveway advice given was incorrect and would have most likely resulted in a leak worse than the current, leaky seal.  

[bjatwood]

Not going to nit pick any written posts with you guys.