Topic: Tach Seal

[DaveInTexas]

Well I looked in there and without ref'ing a parts manual it looks like a flat rubber washer with a 1/8" hole in the center and a metal housing beneath, and encircling it, in there. 

The tach fitting (the end of the cable) which goes in there can be easily moved 1/8" fore and aft.
Is this about right or is there something wrong there?

[Chris Liston]

The tach cable does the same on my 76' 550..  I can move it slightly fore and aft. 

[Raul CB750K1]

Yep, you can move the drive a little, but the seal is indeed a seal, not a simple washer. That is, it has a lip inside to keep the oil from going out. Available from Honda. Use a wood screw to get it out by screwing in and pulling (Bryan Jones dixit)


Raul

[eurban]

The seal for the tach is actually a seal for the tach drive shaft that pokes it little head (from underneath the cover) into the hole in the cam cover where the tach cable end housing fits into and where the tach drive cable mates with its prong.  The seal is pressed in from the outside. Think of it as a minature version of the seal on the gearshift lever, drive flange etc etc.  For my 78 750 I used the seal for the later DOHC 750s because it was reported (can't remember where I heard to do this) to be a better designed piece that lasted longer.  I compared a new version of both seals and the sizes were essentially the same with slight differences in the seal design.  This DOHC seal has worked fine for over 2K.  The fore aft play in the housing is a function of the play where the set screw fits into the groove on the cable housing.  Make sure that the set screw is properly tightened down and of the correct length.  Some play is normal and this has no effect  on oil seepage since the oil sealing is unrelated to the end housing on the tach cable. 

[Boomologist]

It is definitely a seal that resembles the type on the end of your crank shaft, only lot's smaller.
It measures 14.5 outside x 5.8 inside x 4 mm thick. Honda dealer here states they are no longer available.