Topic: Massive Leak after rebuild - cb750K1

[Prospect]

Freshly rebuilt engine and the oil is leaking out like crazy out of the transmission cover.  I mean when you take the cover of and turn over the engine the oil is leaking like you've turned on a tap.   If you look at the pictures from before the rebuild that hole was mysteriously covered.  This is where most of the oil is coming from.  What is the purpose of the hole?

Showing oil leak


Hole is covered (before rebuild)



There is also a hole that I never noticed before right below the gearshift shaft.  It's big enough to see right inside to the gears. Some oil is coming out from there too. 

[MCRider]

There should be a rubber plug in the first hole. I don't think the gasket alone can do the job. As to its purpose, such things are usually an aid to the manufacturing process, often happens in carbs, where they drill a hole to get access to another process, then plug the hole.

The second issue is fine. That is the return path for the oil that is squirted into the shifter cover to travel back to the sump by gravity. If the bike is vertical, the oil would be running into the sump rather than into the shifter area.

[Prospect]

There should be a rubber plug in the first hole. I don't think the gasket alone can do the job.

Thanks for the reply.  I didn't see the rubber plug in the parts fiche??

I'm also getting a good leak from the counter shaft top gear?? 

[MCRider]

There should be a rubber plug in the first hole. I don't think the gasket alone can do the job.

Thanks for the reply.  I didn't see the rubber plug in the parts fiche??

I'm also getting a good leak from the counter shaft top gear??

I looked too, out of curiosity and didn't see it. I don't think its available. It should never be removed and hence never replaced. There was another thread about this, and it forced me to pull my trans cover and look as i didn't remember if mine was there or not. (fresh rebuild). It was there. Time to source one, hardware, another case, etc.

If you mean the bearing that you can see from the shifter cover, it should allow oil to pass into the shifter area.

If you mean the drive sprocket, that's the chain oiler working overtime. You can turn it almost off with the adjusting screw, or remove it and screw a plug in. Watch that you have the correct thread and length. The threaded part of a spark plug will work.

[Prospect]

Yes, I meant from the bearing behind the shifter cover. I didn't realize that so much oil is pumped into the shifter cover.  It's quite a bit.

As for the missing rubber part I'll have to borrow one from my "parts" engine.  Hopefully that one has one.

Thanks again MCRider.  I think I was in the middle of a mild heart attack when I saw all that oil coming out.  Your answers calmed me down a bit.

[Brantley]

Yeah, it's not on any fiche I've seen or my old parts book. Ron, you may be talking about my post a few years ago when I was super confused thinking I'd lost that plug in my K0 case when it was apart (reason to remove it- aircraft remover)? After comparison to a K1 case I had (and looking at photos I took during disassembly) it turns out mine wasn't even machined to accept that plug, which leads me to believe it's only there to stop oil loss if you need to remove the tranny cover. As my K0 doesn't leak oil at that cover, and if yours doesn't, I'd venture to say you don't need the plug if you can't find one.

[gecko672]

 I also have a 71 and  I remember seeing that hole( the first one your talking about) and wondering about it. I thought I read that on these bikes the gasket covers it. Later bikes had a plug.I just cant remember now where I read it. My cases are back together and although I havent run it on the road it isnt leaking when turned over with the battery. Maybe a bad gasket?
Here is mine when dis assembling. No plug there.


Untitled by crannog, on Flickr

[scottly]

I looked too, out of curiosity and didn't see it. I don't think its available. It should never be removed and hence never replaced. There was another thread about this, and it forced me to pull my trans cover and look as i didn't remember if mine was there or not. (fresh rebuild). It was there.

I remember that thread, Ron, and found that neither my K1 motor or a K7 parts motor had the plug. The gasket seals it off, provided the cover is installed.
Prospect, you do have the cover installed, correct?

[Prospect]

I went to buy some triple trees and gauges this evening an the guy selling them had a spare engine so I got the rubber plug from it. I'm pretty happy about that. I'm really surprised that's not in the parts list.

[MCRider]

I went to buy some triple trees and gauges this evening an the guy selling them had a spare engine so I got the rubber plug from it. I'm pretty happy about that. I'm really surprised that's not in the parts list.

Per Scottly and Gecko, maybe its not necessary. The gasket should do the job. But was yours leaking out on the ground? Was your gasket damaged?

I can see where if you rely on the gasket only, that when you pull that cover you could get excess leakage unless you've got it tipped to the right slightly.

[lucky]

Well you do not have to take the engine all apart!!!

[scottly]

Running the motor with the cover removed, plug or not will result in oil spilling out, IMHO.

[Prospect]

I went to buy some triple trees and gauges this evening an the guy selling them had a spare engine so I got the rubber plug from it. I'm pretty happy about that. I'm really surprised that's not in the parts list.

Per Scottly and Gecko, maybe its not necessary. The gasket should do the job. But was yours leaking out on the ground? Was your gasket damaged?

I can see where if you rely on the gasket only, that when you pull that cover you could get excess leakage unless you've got it tipped to the right slightly.

It's a new undamaged gasket from Athena.  Maybe the cover wasn't tightened all the way to spec.  It was leaking moderaltely with the cover on onto the ground and once I took the cover off I was alarmed as to the amount of oil in there.  It all makes sense now but was a little startiling at first.  I'll put in the rubber plug that I got today and tighten everything up. 

[Prospect]

So this was the piece that is missing.  Very odd that it's not in the parts list. 



Installed and no apparent leaks so far.

[MCRider]

Ta Da!