Topic: Shift Case Oil Leak?

[yhwu]

I've noticed an oil leak from the bottom of the shift cover on the left side. I took the cover off and quite some oil spilled out. I thought it was the shifter seal at first but even though it's pooling on the bottom right hand side of the shift compartment it seems like it is coming from somewhere else...I'm guessing definitely some kind of seal...any ideas? Any help will be appreciated!

[yhwu]

More pics for reference

[HondaMan]

It is normal for oil to be at that level: the dry-sump side of the oil pump leaves about 1" deep oil in the pan while the engine runs. It is fairly common for that cover to weep oil on the engines made before 1975 because the side covers were not de-stressed, just flat-ground. If you suspect the cover may be slightly warped now (which I have sometimes seen) you can have a machine shop flat-grind it for you, for $40-$50.

Make sure someone (before you) hasn't gouged the gasket surface somewhere when removing a stuck-on gasket, too. If it is, I use some Hondabond (for small gouges) or Permatex#2 (for deeper ones) on both sides of the gasket at the gouge site. I don't suggest using it all around this gasket, or you may never be able to remove this cover again if you need to: there just isn't many places to pry it off the engine!

[yhwu]

Phew! So sounds like everything is normal except the cover itself is leaking? Seems kind of interesting that they're keeping it sealed with metal-on-metal contact...but hey, I trust the engineer!

[scottly]

What do you mean "metal-on-metal contact"? Was the gasket missing? Also, the cover limits the end-play of the shifter shaft, and if the sealing surface is ground down too much it will bind.

[yhwu]

Welllllllllllll guess that's the problem! 😂😂 I was wondering why there isn't a gasket...

[scottly]

 

[yhwu]

Been riding my bike for a year or so and 1k+ miles on it and it only started leaking now...that's crazy

[yhwu]

Sooo...replaced the gasket but found out that it's now leaking from behind...not sure what's behind the cover other than the crankcase...if anyone wants to point me in the right direction I'd appreciate

[scottly]

What year is your bike? That's the sprocket cover over the front sprocket. Some models have an "automatic" chain oiler built into the center of the output shaft.

[yhwu]

It's a 1976 F model, not sure if mine has it, but from my 30 second google search it looks like the seals might be worn and something to do with plugging it with an old spark plug?

[scottly]

There are better ways to close off the oiler than a spark plug, but I don't know if your F has one. There is also a seal for the output shaft behind the sprocket, but they rarely leak.

[scottly]

Here's a pic of the seal, and you can see my homemade plug for the chain oiler.

[newday777]

It's a 1976 F model, not sure if mine has it, but from my 30 second google search it looks like the seals might be worn and something to do with plugging it with an old spark plug?

The 76F didn't have the automatic chain oiler. It should have a solid bolt head without the adjuster screw in the center holding the sprocket.

What could be causing the leak there you have is oil leaking out the neutral switch and traveling/flowing in the wind back to the foot peg mount/sidestand boss and down. I had to put in a new neutral switch because of that oil leaking last year on my K5 (after I had fixed the leaking auto chain oiler and it was still getting oil traveling back there). Finally no more oil leak!
The neutral switch is under the motor about where the shift shaft comes through the trans cover. It has phenolic(red arrow) plastic to isolate the wire screw boss that gets brittle and leaks oil eventually.
Some have sealed the leaking switch but replacement is best.
http://forums.sohc4.net/index.php?topic=51630.0

http://forums.sohc4.net/index.php?topic=160609.0

When changing the switch, have the bike in neutral and don't move the gear lever while the switch is out, the switch holds the drum from moving laterally.
When installing the new switch, put oil on the new oring and then put the oring in the hole first pushing up in fully, then put the switch in, oriented so the bolt plate holder(#27) sets on the squared edge properly.

You will need a new oring for the switch(#31) for the switch (#26)
https://www.southsoundhonda.com/--xpartsstream#/Honda_Powersports/CB750FA_(76)_750_SUPER_SPORT%2c_JPN%2c_VIN%23_CB750F-2000003_TO_CB750F-2022317/GEARSHIFT_DRUM_%2b_SPINDLE/e65ffa8d-6805-4211-95ff-c44dded3b19c/a6f2e457-58a7-4f33-8177-adfba9bf97b5/y

[Johnie]

Just another thought here...I had same issues on my KO years ago. Put in new cover gasket still leaked. Finally resolved it...the rubber grommet that sealed the alternator wires were leaking.

[yhwu]

Great info guys!! Never would've thought of things like that...sounds like I have some parts to order now, will update if it ever is resolve