Author Topic: Oil from front sprocket area (Read 8782 times)

Cartman98 · « **on:** August 25, 2009, 03:05:14 PM »

One of my many oil leaks that have sprung up in the last week since I have bought my '75 750 is around the front sprocket. I'm still not sure where it is from exactly. This one is probably the worst. Any ideas? I've read something about from the oil pump o-ring, the wire grommet next to the sprocket cover, and the shifter seal.
Also seem to be loosing oil from the valve cover or head gasket, and now I've found a leak in the master cylinder around where the brake lever is!

Any suggestions of probable locations is appreciated!!!!
Oh, and I tried to remove the shifter cover... ended up drilling out 3 of the screws that I stripped the heads on... and figured out that the cover was sealed...
First restoration project, how fun!

bistromath · « **Reply #1 on:** August 25, 2009, 03:22:18 PM »

Buy an impact screwdriver, a soft-face mallet, penetrating oil, and a workshop manual. The sprocket cover is not sealed.

kghost · « **Reply #2 on:** August 25, 2009, 03:28:23 PM »

Theres only two places to leak from around the sprocket.

Chain oiler and the seal behind the sprocket.

Duke McDukiedook · « **Reply #3 on:** August 25, 2009, 03:36:36 PM »

Did 75's have an oiler?
I thought they ditched that after the K2-K3?

Cartman98 · « **Reply #4 on:** August 25, 2009, 03:39:17 PM »

I don't know, but is it known to leak badly? There is quite a lot of oil built up around that cover.

An impact screwdriver is an air-tool?

bistromath · « **Reply #5 on:** August 25, 2009, 03:43:36 PM »

http://www.sears.com/shc/s/p_10153_12605_00947641000P

srook · « **Reply #6 on:** August 25, 2009, 04:40:35 PM »

Can the countershaft sprocket seal be installed without splitting the cases? I am assuming I can just remove the sprocket cover, sprocket and then pick out the old seal and install a new one. Is this correct?
Scott

bryanj · « **Reply #7 on:** August 26, 2009, 06:02:10 AM »

Nope, it has a lip on it that sits in a grrove, But you have to take the engine out to remove the cam cover and fix the head leak so do it all

ev0lve · « **Reply #8 on:** August 26, 2009, 06:52:40 AM »

Quote from: Dukieballz on August 25, 2009, 03:36:36 PM

Did 75's have an oiler?
I thought they ditched that after the K2-K3?

They do. Forgot to tighten mine up all the way when I got it back on the road. Left a real nice puddle of oil under the kickstand.

bikerbart · « **Reply #9 on:** August 26, 2009, 08:31:54 AM »

An Impact driver is not an air tool,you hit it with a mallet or hammer;Impact.Everyone who wrenches should have one.They are relatively cheap.

vames · « **Reply #10 on:** August 26, 2009, 08:42:45 AM »

This could also be the seal around the shift lever shaft. That's an easy one to replace -- no need to split cases or anything. Lots of threads describe the method needed to change it.

754 · « **Reply #11 on:** August 26, 2009, 09:42:19 AM »

Check for broken chain caused, case repair..

Cartman98 · « **Reply #12 on:** August 26, 2009, 02:48:34 PM »

I tried to find the shift lever shaft seal and found that under the oil faq section. I ended up taking off both the cover that the shifter was through and the cover for the sprocket. I didn't find an O-ring as described in the threads about it... It looks like it comes from somewhere in the sprocket area though.

Quote from: vames on August 26, 2009, 08:42:45 AM

This could also be the seal around the shift lever shaft. That's an easy one to replace -- no need to split cases or anything. Lots of threads describe the method needed to change it.

MCRider · « **Reply #13 on:** August 26, 2009, 02:58:54 PM »

Quote from: Cartman98 on August 25, 2009, 03:05:14 PM

One of my many oil leaks that have sprung up in the last week since I have bought my '75 750 is around the front sprocket. I'm still not sure where it is from exactly. This one is probably the worst. Any ideas? I've read something about from the oil pump o-ring, the wire grommet next to the sprocket cover, and the shifter seal.
Also seem to be loosing oil from the valve cover or head gasket, and now I've found a leak in the master cylinder around where the brake lever is!

Any suggestions of probable locations is appreciated!!!!
Oh, and I tried to remove the shifter cover... ended up drilling out 3 of the screws that I stripped the heads on... and figured out that the cover was sealed...
First restoration project, how fun!

I vote for the chain oiler on probability. To address several of the posts as well as yours:
The chain oiler I existed on all CB750s just with some modifications thru the model years. (I just confirmed that by looking on the K5 parts diagram at Motogrid.com. You're bike has an adjustable chain oiler.) If it is not turned completely off (in which position it still allows some oil) it will make a unholy mess. Many of us will "stuff" the hole to shut it off completely and just lube the chain manually.

The CS sprocket seal could be leaking, but it is way down my list, virtually indestructible, unless this bike had a chain failure as one alluded to. It does require a complete teardown to replace, but it is a tough bird.

cookindaddy · « **Reply #14 on:** August 26, 2009, 03:42:00 PM »

I second the suggestion for chain caused case damage, I have this on mine. PO had the chain come appart I guess. You have to look in behind the sprocket to see where someone "fixed" mine with a piece of sheet aluminum and some glue of some kind. It doesn't leak too badly, but it does leak. I'm working on a replacement engine since this problem can't be fixed from the outside.

Cartman98 · « **Reply #15 on:** August 26, 2009, 08:17:18 PM »

In reply to the case being damaged, I didn't notice any under the cover, having cleaned everything out of there. I did not have the sprocket off and it looks original, so I doubt there is any problem like that.
As for fixing cracked case, I had that happen on an atv of mine where the chain broke, wound up around the countershaft sprocket and cracked the case. I had a mechanic weld it up and it worked fine for years afterwords.
I'll have to look, but is the chain oiler obvious? I'll try to look through the shop manual, but sometimes that stuff is hard to find in the diagrams.

ev0lve · « **Reply #16 on:** August 26, 2009, 09:45:16 PM »

Quote from: Cartman98 on August 26, 2009, 08:17:18 PM

I'll have to look, but is the chain oiler obvious? I'll try to look through the shop manual, but sometimes that stuff is hard to find in the diagrams.

It's the screw with a slot right in the middle of the sprocket.

kghost · « **Reply #17 on:** August 26, 2009, 11:05:13 PM »

If the bearing the sprocket shaft rides on gets worn...it will walk that seal right out.

The seal behind the sprocket is fairly large and you should see it sitting flush with the case.

I had one walk out last year on a 72 model thats fairly high milage.....55,000 plus miles.

srook · « **Reply #18 on:** August 27, 2009, 07:15:30 AM »

If that seal can walk out, why can't a new one be pushed in without splitting the cases?
Scott

Cartman98 · « **Reply #19 on:** August 27, 2009, 11:18:48 AM »

Thanks much, pictures are always helpful! I checked mine just now and that screw was about 4 turns out! I am only guessing, but when you turn it in, it is shut off? How do you shut it off completely?

Quote from: Iggy on August 26, 2009, 09:45:16 PM

Quote from: Cartman98 on August 26, 2009, 08:17:18 PM
I'll have to look, but is the chain oiler obvious? I'll try to look through the shop manual, but sometimes that stuff is hard to find in the diagrams.

It's the screw with a slot right in the middle of the sprocket.

MCRider · « **Reply #20 on:** August 27, 2009, 12:07:35 PM »

Even if you wanted to use it, 4 turns out is too many. Yes, turning it in until the head of the screw is so flush you can't turn it any more is to the off position. That may be good enough for you, you may want to try it.

And you may still have other problems as well, like the CS seal.

To plug it, remove the 17mm nut that the adjuster screw goes through. THe adjuster will come out with it. The adjuster that you can't see is actually a bit of an affair, there is a small plate that squishes a rubber plug. All that stuff comes out.

Run a bolt in that is long enough to cover the hole where the oil comes out. It is in the CS about centered in a spot about halfway under the sprocket. You can't see it unless you take the sprocket off. THe length of an "E" size spark plug is likely the length you need. I've heard that you can break the ceramic top off a spark plug and run that in to plug it. Use the tabbed lock washer to hold it there.

Others have removed the sprocket and threaded a bit of rubber, like an O Ring that has been cut, into the hole, that trick is on this site soemwhere, maybe search Tricks and Tips.

kghost · « **Reply #21 on:** August 28, 2009, 11:41:20 AM »

Quote from: srook on August 27, 2009, 07:15:30 AM

If that seal can walk out, why can't a new one be pushed in without splitting the cases?
Scott

It can be.

I never said it couldn't be.

I glue them in.

climbingaz · « **Reply #22 on:** August 28, 2009, 12:43:20 PM »

Great info guys, as usual. Gotta look at this on my bike too.

srook · « **Reply #23 on:** August 29, 2009, 02:45:17 AM »

"I glue them in."

I am not trying to be difficult but why does the seal need to be glued in? Maybe I should explain my situation. I am doing a top end on a CB750. I do not want to split the cases. The bike runs well and there were no transmission issues. While degreasing the motor for paint I used lacquer thinner which ran all over that countershaft seal as I was cleaning the gunk off the cases. I am assuming the seal is toast because of its contact with lacquer thinner. It didn't leak before hand. I just want to be sure I can change out the countershaft seal without splitting the cases. So far I have 2 you have to split the cases and 2 no you don't. If the seal does not have a lip on the inside then I don't see why I would need to split the cases, but if the seal is so loose fitting that it needs to be glued in, then maybe I should split the cases. Any help on this would be much appreciated.
Thanks
Scott

cookindaddy · « **Reply #24 on:** August 29, 2009, 04:09:39 AM »

About the chain oiler being on all model 750Ks:

My daily driver is a 78 K8 and it doesn't have the chain oiler. Thanks for the excellent pic, now I know where it is supposed to be. There is a solid bolt holding the drive sprocket.

I also have an engine here that is awaiting rebuilding from a 77 (K7?). It too has a solid bolt holding the drive sprocket.

The chain oiler sounds like it would be a neat thing to have and I suppose that I should pull the sprocket off and look down the hole to see if there is an oil passage there. I'm guessing the chain oiler is something that I could add?

Can anyone else confirm that K7 K8 did NOT have the chain oiler? Perhaps my two engines had the chain oiler removed.

Thanks.

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Author Topic: Oil from front sprocket area (Read 8782 times)

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