Right Crankshaft Seal

dkwilfert · Post by **dkwilfert** » Mon Nov 09, 2009 5:10 am

Now that I have my 63 CB77 back in a riding condition, it has developed an oil leak on the right side that appears to be the crankshaft seal (behind the generator). Haven't done any disassembly yet to confirm this, but there isn't much else it can be. I haven't had one of these engines apart since 1966 so my memory is weak on this.
1. Do the cases have to be split to change that seal?
2. Any information on a source for a new seal?
Thanks for any help.

mike69 · Post by **mike69** » Mon Nov 09, 2009 6:14 am

You just have to pull the rotor to get to the seal. Don't have to split the case.

You will need a puller to remove the rotor. I have some new metric bolts that I use to pull the rotor,
just screw it in and the rotor will pop off.
pm me if you need one.

You would probably be better off buying a complete seal kit for your bike. If one seal is leaking the others won't be far behind. Ohio cycle has them, and possibly Retro bikes.

gramey7 · Post by **gramey7** » Mon Nov 09, 2009 10:03 am

Another thing to be careful of is to ensure that the replacement seal is pliable enough to seal. I rebuilt my engine a few years ago with what must have been a genuine OEM seal kit (I mean probably 40 years old) and the seal was so hard it would not seal and seeped oil. Replaced with a newer pliable seal and fixed the problem.

e3steve · Post by **e3steve** » Mon Nov 09, 2009 10:50 am

I totally agree with the guys' diagnoses and advice. I've done all my seals on that side but it still drips; I did discover that it's not the seals that are now causing the problem -- it's the upper/lower crankcase facings.

One other thing to watch for: when replacing the clutch pushrod seal, check for a wear groove in the rod where the seal sits. If it is grooved then it won't seal 100%.

Most bearing suppliers or hydraulics shops sell the seals, and they're very inexpensive. Sizing is shown, in mm, on the side of each one. The pushrod seal is 8-21-6, which directly translates to 8mm x 21mm x 6mm (ID x OD x W).

davomoto · Post by **davomoto** » Mon Nov 09, 2009 4:56 pm

There are 2 seals behind the stator, the crank seal, and the starter sprocket seal. replace bot, leave nothing to chance.

davomoto

dkwilfert · Post by **dkwilfert** » Tue Nov 10, 2009 5:25 am

Thanks guys, appreciate all the help. I know my leak is behind the generator rotor and not around the clutch rod because of the location of the drip. There are drain holes on that side case between the clutch rod and the rotor and the drip is well forward of the drain holes.

Tip for all if my memory is correct. For pulling the rotor, one of the axles (can't remember if it is front or rear) has the correct thread to screw into the rotor and pull it off so you don't need to buy a separate puller.

Just happend that the yesterday morning there was a new Ebay listing for a new crankshaft oil seal (32x65x7.5) with a reasonable "Buy It Now" so I bought it. As a bonus the guy is also shipping me a transmission shaft seal (30x62x8) at no additional cost. Kind of scary, seems too good to be true, but the seller has outstanding feedback history.

Thanks again. When I get around to doing the repair I'll post a followup.

G-Man · Post by **G-Man** » Tue Nov 10, 2009 6:52 am

As a Brit it's just wonderful to hear stories of Japanese bikes leaking oil. We felt so inferior when these super machines came out which 'never leaked'.

We should have realised that oil has a strong natural urge to get back into the ground where we pumped it from........ :-)

Keep up the good work. I have a small stock of the big CL77 seals (different than the CB) seals.

G