Topic: CB750: tach seal leaks. Replace w/ DOHC seal?

[Tugboat]

I've already replaced my leaky tach seal on my '77K motor once, and it still leaks. Maybe I didn't to it right? Regardless, supposedly the DOHC tach seals are 1mm thicker. Has anyone successfully replaced their SOHC tach seal with one from a DOHC motor?

[ekpent]

 Never tried the DOHC seal but have read where others have. I have replaced quite a few with the OEM stock part for the year and have not had one leak again yet. Its ironic that you posted this because I actually need to restock up on those as a bike I am working on now needs one replaced. 

[trenchgrinder750]

I just replaced the tac seal on my 78 750f with an OEM and so far so good.  12mm socket to seat it with a couple lite taps from a deadblow.

[2wheels]

My replacements leak as well.
Please post the part # if you buy the DOHC one.
So I can try it.

[disco]

Sometimes it can be difficult to determine that the old seal is completely removed. Check that you got the old seal out entirely. They often leak because either a) seal remnants are left in there or b) the entire seal has not been removed!

I've not had one leak when the seal has been properly removed. Like trench said, drift the new seal in with a suitably sized socket. Then she'll be apples.

[evanphi]

I gave my tach cable a quick wrap of PTFE tape to help it seal completely. New seal back there in a cleaned out hole.

[Tugboat]

Thanks for the tips fellas. Gonna give it a go with a new SOHC seal this weekend.

FWIW, the part number for the DOHC seal (4.8x14.5x5mm) is 91256-425-003.