Author Topic: 73 CB750 countershaft seal (Read 4681 times)

My73andme · « **on:** August 10, 2018, 06:04:55 PM »

Hello everyone I just picked up a 73 CB750 and I rode it for a couple days and then started diving into getting things up to speed and cleaned up for safety and prefernace. Anyway I got a chain and some new tires. I knew before buying it that it had a leak but it didn’t drop barley any. When I went to change the chain I noticed that the front sprocket was loose and there was years of oil :/ my front sprocket also had alittle play (is that normal) since there was so much oil I just figured that the countershaft oil seal needed replacing. I was able to remove it with the wood screw and vice grips method easily but when I went to go put the new seal in I ruined it

I ordered a new one so it’s on its way.

My question is on the wisdom about having to take the case apart to install?? I have read a hundred posts in 15 different forums and basically there’s the people that say yes you have to take the crank case apart and there’s people that say no. There’s also people that say that their seal has a lip that fits in a groove and that’s why you have to take case apart. There’s also people that haven’t seen a seal with a lip. I am that person. The seal I removed didn’t have a lip and the seal I tried to install didn’t have one. Please if you have done this WITHOUT taking case apart and have the tricks to help me that would be so grateful.

Thanks so much

disco · « **Reply #1 on:** August 10, 2018, 06:47:31 PM »

The seal behind the front sprocket doesn’t have a lip to it. You can replace it without splitting the crankcase. You might have to make a tool to drift it into place, without damaging it. You want to apply force evenly around the seal. A suitably sized piece of pvc pipe might work?

The seal on the crankshaft that sits behind the points plate, that has a lip on it. To replace that one, you need to split the cases.

Btw front sprocket play is normal. The sprocket floats on the shaft.

My73andme · « **Reply #2 on:** August 17, 2018, 07:55:34 PM »

I have already ruined two seals. It seems like the edge of where the seal sits in the case starts to shave off the outer rubber of the seal

I have tried to be so gentle so same things has happened to both. I’ve got two more seals coming. I’ll try once more and then I guess I’ll have to split the case.

Davez134 · « **Reply #3 on:** August 17, 2018, 09:06:59 PM »

That seal does not have a lip. I replaced one without splitting the cases, but you have to drive it in absolutely square. I lightly removed any burrs in the cases, then coated the edge of the seal with Hondabond. It acts as a lubricant when installing and seals when done. That oil could have been from too much oiling of the chain. I do not believe your bike had an automatic chain oiler, but someone could have manually overdone it. post a picture of the end of the shaft with the sprocket installed. Also, I have a bit of play I the sprockets of both my CB's.

My73andme · « **Reply #4 on:** August 17, 2018, 10:15:52 PM »

I heard from a vintage motorcycle shop that I might have a different year engine as they got swapped a lot. My seal doesn’t have a lip. I am ordering oem parts from a Honda motorcycle shop near me. Anyway I’m trying to post a photo but can’t figure out how hahaha the sprocket it already off and the seal is in but it’s not correct and it’s damaged. I had the same thought about the previous owner over piling the chain as there was so much old gunk in there. I should have just cleaned the area ride it and then checked to see if it was the seal leaking. I regret pulling out the seal before making sure it was the seal leaking

((( the seal came out so easy with the wood screw method.

My73andme · « **Reply #5 on:** August 17, 2018, 10:28:40 PM »

Here’s the wood screw method and the countershaft without the seal. It was way way dirtier. I will post more pics of the current seal that is in there now as I left it in so I could finish cleaning the area while I wait and try figuring out this stupid but learning situation

PeWe · « **Reply #6 on:** August 17, 2018, 10:32:27 PM »

Make sure that the automatic chain lubrication that does not splash oil before replacing the seal. The small screw in the shaft has to be tightened. If not it will splash oil to lube the chain and it will drip oil close to the center stand foot.

My73andme · « **Reply #7 on:** August 17, 2018, 10:38:09 PM »

I don’t think my year had an automatic Oiler. There’s no screw from what I can see that would indicate that.

My73andme · « **Reply #8 on:** August 17, 2018, 10:41:18 PM »

Ok here is the countershaft without seal and a couple pics of the damaged seal I left in so that I could finish cleaning the surrounding area. It may look in but it’s totally fudged! I also put some electrical tape around the shaft to help protect it from trying to drive the seal just encase you all are like what the poop is that?

PeWe · « **Reply #9 on:** August 17, 2018, 10:49:07 PM »

It will leak a lot of oil since the oiler parts are completely missing
See here which parts
https://images.cmsnl.com/img/partslists/honda-cb750k3-four-1973-usa-final-driven-shaftdrive-sprocket_bighu0105e1321_95cf.gif

My73andme · « **Reply #10 on:** August 17, 2018, 10:50:54 PM »

Ah missing huh?? You thinks it’s completley missing. Well ok then I will get those parts with my next order of things 👌🏻

My73andme · « **Reply #11 on:** August 17, 2018, 10:55:28 PM »

So 7 15 6 are the parts I need that fit into the shaft that will help not dump oil all over everything once I get this seal thing figured out?

What about 2 8 11 5 ?

PeWe · « **Reply #12 on:** August 18, 2018, 12:20:15 AM »

You can close it completely. Here one alternative. There are others too
https://www.ebay.com/itm/HONDA-CB450-CL450-CB750-CHAIN-OILER-OIL-VALVE-PLUG-23311-319-320-23523-300-310/221999825230?hash=item33b038814e:g:rvQAAOSwYGFUwHwV

My73andme · « **Reply #13 on:** August 18, 2018, 07:20:30 AM »

The threaded end looks to big for mine. The hole on the shaft that’s coming out is probably smaller then a 1/4 inch. But yes I feel like the plug is the way to go and then just manually oil the chain.

My73andme · « **Reply #14 on:** August 18, 2018, 11:18:44 AM »

Back to any tricks for correctly driving this countershaft seal without splitting the case?

??

I heard heat gun the case and freeze the seal...thoughts???

Davez134 · « **Reply #15 on:** August 18, 2018, 12:00:07 PM »

Quote from: My73andme on August 18, 2018, 11:18:44 AM

Back to any tricks for correctly driving this countershaft seal without splitting the case??? I heard heat gun the case and freeze the seal...thoughts???

Here's what I used to drive mine in:
http://forums.sohc4.net/index.php/topic,139768.msg1800703.html#msg1800703

Again make sure there are no sharp edges on the case, (I actually used a Dremel to put a very VERY slight bevel around the outside edge of the hole in the case. You cant even tell by pictures) coat the seal edge with Hondabond.

My73andme · « **Reply #16 on:** August 18, 2018, 12:30:36 PM »

Awesome. What size pvc?

My73andme · « **Reply #17 on:** August 18, 2018, 07:11:58 PM »

Thanks so much I built my pvc driver today and now just have to wait for my seal. I ordered 2 :/ I’m a bit 😬

754 · « **Reply #18 on:** August 18, 2018, 07:44:20 PM »

Maybe you have a late motor, then there is no groove aroundvtge sprocket shaft about 3 or 4 mm from end of shaft.
What is engine serial number?

HondaMan · « **Reply #19 on:** August 18, 2018, 08:03:12 PM »

The shaft looks to be standard K3, except it is missing the end pieces that go on after the sprocket is slipped onto the shaft. Those end pieces are the oiler adjuster (regulator, Honda called it) that pinches off the open center of the shaft to make more (or less) oiling happen above 30 MPH. Without those pieces, it will oil A LOT!

I have never been able to install the countershaft's seal without having the cases apart.

My73andme · « **Reply #20 on:** August 18, 2018, 08:25:04 PM »

Here’s a semi good photo of the numbers in my engine. Let me know what you think but with all this about a seal with a lip and a groove I’m guess mine is later as I don’t have either.

CB750E - 2437088

My73andme · « **Reply #21 on:** August 18, 2018, 08:30:03 PM »

754 are you taking about this groove...?

My73andme · « **Reply #22 on:** August 18, 2018, 08:36:58 PM »

Sorry for all these post I guess I could have combined them. What is the E after CB750 mean?

HondaMan I ordered a plug today for the end of the shaft where the Oiler would go. Bummer to hear about having to split the case to put the seal in and I may have to do that but I’m going to try one more time 🙏🏾🙏🏾🙏🏾🙏🏾🙏🏾🙏🏾🙏🏾🙏🏾🙏🏾🙏🏾🙏🏾🙏🏾

754 · « **Reply #23 on:** August 18, 2018, 09:47:59 PM »

Yeah that groove it looks like correct motor, and it did have an oiler.

I forget the thread pitch, but if you made a cup to fit outside of seal, with a center hole for the bolt. Then make a threaded rod for the end of shaft, or all thread if it exists.
You could then use a washer and nut against the cup, to draw in the seal, nice and straight and evenly..

My73andme · « **Reply #24 on:** August 18, 2018, 09:56:35 PM »

754 I don’t fully understand what you’re taking about sorry man. Are you suggestion that you can use that groove to push the countershaft seal in evenly somehow..?

Yes I ordered a plug for the Oiler spot that Davez134 suggested.

754 · « **Reply #25 on:** August 18, 2018, 10:45:47 PM »

You need at least a vernier caliper to do this, access to a lathe, even better..
Insert a threaded piece into end of shaft, it threads in.
And make a cup to fit outside of seal, with a hole in the middle of the flat part that fits over the rod ..think spray bomb lid with hole in the end but metal.
Now place it over the threaded part, and touching the seal, then use a washer and nut on the threads, to pull cup and the seal towards the engine case.

Failing making a cup you could use PVC, cut to length accurately, and a big washer.
I think hole in shaft might be for 14mm thread. Maybe just maybe 1.0 pitch.

My73andme · « **Reply #26 on:** August 19, 2018, 05:26:22 AM »

Ok ok I understand now that’s a really good idea but I don’t have that kind of set up

I will try my pvc tool 🙏🏾 Thanks so much for your wisdom

My73andme · « **Reply #27 on:** August 25, 2018, 08:18:32 PM »

I guess I don’t have an Oiler so the hole at the end of my shaft is smaller. Do you know the size and thread of that hole at the end of my shaft?

My73andme · « **Reply #28 on:** August 26, 2018, 06:06:22 PM »

I got the seal in today. It was my 3rd try at the seal without splitting the cases. I did use a couple different methods and I’m not 100% sure it will work. But I want to put the bike back together and ride it so we shall see if it will work. If not I’ll pull the motor and split the cases.

The seal isn’t perfectly flush with the cases but only at the bottom like an 1/8” I will probably get it flush before it’s all said and done but it’s good enough for now I suppose.

Thanks for all your help.

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Author Topic: 73 CB750 countershaft seal (Read 4681 times)