Topic: Leaky tachometer ouput

[70CB750]

On the valve cover.

I used just a generic o ring there, but it did not work so well so i found a seal that belongs there - by the part number.

It still leaks, any tricks to it?

Not sure it matters but the engine is 78SS CB750.

[jgger]

Is your oil breather tube clear? Just a thought.

[70CB750]

Good point, I will check.

[spotty]

get rid of the tacho, epoxy a coin over the hole...sorted, well it sorted it on my old 750 anyway but that didn't have a speedo either

[ekpent]

Did you seat the seal in well with a socket a little smaller then the fitting hole ? Couple light taps with a small hammer.

[JerryWayneCattle]

Make sure there isn't an old o-ring still deep in there. PO of my '74 CB750 had the correct seal AND an o-ring in it. He might have not even known. It held the cable out and didn't let it seat correctly.  I bought a new one that fits a DOHC 750. Read on this site that they fit better.

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[PeWe]

Correct oil seal will not leak. If hammer too hard the bottom of the cover can crack, alu chunks fall into the cam holder.  Especially when removing the old seal with tools from the outside. Somehow, I know
Frame kit is good in that kind of situation.

[Marks78]

I'm not positive (as I can't find the reference) but it seems like HondaMan recommends using the tach seal from a double overhead cam Honda as a viable alternative. The DOHC seal is just a tad bigger, so it seals better. Best of luck!

[evanphi]

Mine leaks also, and also with a properly seated new rubber seal. I did just a few wraps of PTFE tape on the end of the tach cable and that snugged it up perfectly. No more leaking.

[70CB750]

Well, turns out if was a false flag.  The tachometer cable sheathing was cracked quite a bit and the oil was leaking from there. 

Luckily I spotted it before digging out the seal