Topic: Clutch won't disengage: different mainshaft?

[stueveone]

Hey guys,
cb750 with trans parts from different bikes (!!!!!)
So I'm having an issue with my clutch not disengaging. This is a fresh tranny up rebuild where I had to source different parts from ebay to piece her together. So, the issue: with the pressure plate and springs completely removed, the motor and rear wheel are still connected. Also, with the clutch pack installed without the thrust washer, the pack then becomes flush with the spindle and seats correctly. With the trust washer, it backs the whole pack out the width of the washer.
See photo
Is it possible that this mainshaft is out of a k6 or different bike requiring a different, thicker basket? It looks different than the other motor that i have lying around...

Thanks for your help!

[stueveone]

Yeah, just looked at a fiche for a 76... Seems to be there is some kind of circlip listed, and when looking at my mainshaft, you bet there is a location for a circlip. So, then, any idea what parts I need to order? Circlip, basket? Will everything else work? Ah hell...

[stueveone]

So, to recap... It looks like I have a k6-k8 mainshaft in a k4 engine case with k4 clutch components. After comparing parts microfiche from a k4 to a k6-8 I found the following parts that are different between the two models and that will need to be replaced for my swapped set up:

1. clutch center part # 611690
2. Washer 726068
3. Circlip 727794
4. clutch outer 611690
5. friction disc B 612444
6. steel plate B 612542

Can someone please verify this?

Thanks!

[lucky]

You have a K4. The problem is when you say K6-K8 parts. What year are they?

You cannot use a microfishe because many times Honda has different part numbers for the SAME part used on other bikes.

The K8 1977-78 model had  the most improvements of all the SOHC CB750's.
Including a different clutch. 4th and 5th gear ratios were also higher but that probably would not be a problem. STUEVEONE pointed this out.

I would compare and MEASURE the parts to find out the differences.

I think the answer to this problem is  a early model clutch.
Is that countershaft early model or a 1977-78 countershaft?


BTW...A snap ring is a snap ring. No need to change if it is the same diameter. It does not matter if Honda gave it a different part number for different models.

One other thing...
Quote:
 "So, the issue: with the pressure plate and springs completely removed, the motor and rear wheel are still connected. "

That is normal unless it is in neutral.

The THRUST WASHER.
Quote:
"Also, with the clutch pack installed without the thrust washer, the pack then becomes flush with the spindle and seats correctly. With the trust washer, it backs the whole pack out the width of the washer.
See photo"

If that thrust washer is in the clutch area it needs it.
The question will be does the countershaft sprocket still line up?
If the countershaft sprocket does not line up the same as the K4 sprocket then that is going to be a problem to be resolved. And you cannot just move the rear wheel because then the front and rear wheel will not be lined up.

I do not know if a offset countershaft sprocket will mount backwards. Its all just too weird. I would go for a K4 or K5 countershaft and a K4-K5 clutch and your problems should be over.


If another forum member is even more familiar with all these parts differences please step in.

[stueveone]

Hey Lucky, thanks for your reply!
So, I'm a bit confused from your post.
So I can only guess as to what year the MAINSHAFT is that is installed in the motor due to me purchasing it off ebay. Seeing as it has the circlip groove at the end makes me think that it is from a model that used a circlip ie k6-k8 as far as the parts diagrams go.
If that is the case, after reading a bunch of posts as well as confirming it with parts lists and numbers, I think it's pretty safe to say that I have a later model mainshaft installed, and I would need the corresponding later model clutch basket assembly (parts I listed) to fix the situation. That sound accurate?

"I think the answer to this problem is  a early model clutch.
Is that countershaft early model or a 1977-78 countershaft?"
Countershaft? You mean mainshaft? That is what the clutch rides on yes?

"BTW...A snap ring is a snap ring. No need to change if it is the same diameter. It does not matter if Honda gave it a different part number for different models."
I currently don't have the snap ring, as my previous clutch assembly did not require one.

So it is NORMAL for the motor and rear wheel to be connected even when the pressure plate/springs are removed? Meaning, with them removed, I could not even roll the bike forward. This doesn't seem normal to me as the two pieces of the clutch are only held together by those 4 springs and disengage when the actuator arm on the clutch housing cover pushes on the throwout bearing. Is this right?

"The question will be does the countershaft sprocket still line up?
If the countershaft sprocket does not line up the same as the K4 sprocket then that is going to be a problem to be resolved. And you cannot just move the rear wheel because then the front and rear wheel will not be lined up."
I am not sure what the countershaft sprocket, rear wheel, and front wheel have to do with the clutch assembly? Can you better explain this?

Thanks!!!

[lucky]

Quote:
"I would need the corresponding later model clutch basket assembly (parts I listed) to fix the situation. That sound accurate?"

Yes.... that is accurate. BUT the sprocket location on the countershaft lining up with the rear sprocket is still a concern.


QUOTE:
"So it is NORMAL for the motor and rear wheel to be connected even when the pressure plate/springs are removed? Meaning, with them removed, I could not even roll the bike forward. This doesn't seem normal to me as the two pieces of the clutch are only held together by those 4 springs and disengage when the actuator arm on the clutch housing cover pushes on the throwout bearing. Is this right? ?


What is happening is that it is hard to turn over because if you kicked the kickstarter it and it was in gear, it is trying to turn the crank and pistons.

IF it wont roll forward it means the chain to the rear wheel is connected.

Rear wheel TURNS trans TURNS primary chain inside the engine TURNS the crank and pistons.

The whole purpose of the clutch is to take the bike out of gear (unconnect the drive train)  while you shift.


LAST QUESTION:
"I am not sure what the countershaft sprocket, rear wheel, and front wheel have to do with the clutch assembly? Can you better explain this? "

The front and rear wheel of the motorcycle must be in line with each other.
They run down the same line .

If you have the late model K8 countershaft it might not have the countershaft sprocket mounted in line with the rear sprocket. Then the chain will fly off.
And you cannot move the rear wheel over to get the front and rear sprocket to line up because then the front and rear wheel of the motorcycle will not line up.

Try to find out if the sprocket position of the K8 and K4 are the same.
I am sure someone on this forum must know. Like member 754.
I am not sure on that question.

[Don R]

Hopefully you can find the proper assembly of parts. I'm also having a hard time visualizing the clutch being engaged without the springs.

[Jerry Rxman Griffin aka MuthaF'er]

Here are some comparative pictures so you can see some differences

2 different style clutch covers - later on right



2 different 25mm clutch washers - later on left



Newer style clutch basket - picture shows area where the 25mm washer fits "inside"



Older style clutch basket - picture shows area where washer fits on "outside" on top



Early style clutch pack with Barnett plates



Later style clutch pack



Early clutch basket on left & later on right

[Don R]

 A K7 for visual purposes. I believe he said the shaft the clutch is on is the one he changed. Sprocket should not be an issue.

[stueveone]

Wow! Thanks Jerry!
Yup, pretty clear looking at the photo that I have the later style mainshaft which requires the later style clutch assembly. All those parts are on order. You can clearly see the flattened screw boss on the later style cover. Piece of cake to duplicate with a steady hand and dremel. Hell, even with a shaky hand 1/2 a 6'er in could manage it! I will report back my findings!!!!

[lucky]

The transmission has two shafts.

Main shaft and counter shaft. The counter shaft has the countershaft sprocket that connects to the rear wheel.

[mec]

The transmission has two shafts.

Main shaft and counter shaft. The counter shaft has the countershaft sprocket that connects to the rear wheel.

the 750 has one more:
(according to my honda genuine parts list)
23210-300-000 shaft comp., main transmission
23220-300-010 shaft, counter, transmission
23520-300-305 shaft comp., final driven..........this is the one the sproket sits.

mec

[stueveone]

Still not sure how the countershaft or final drive shaft relate to my particular issue?

[Jerry Rxman Griffin aka MuthaF'er]

They don't. You did mention "Is it possible that this mainshaft is out of a k6". What we have to do is get the correct mix of parts in the clutch baskets. Glad you're going to teach me    as I'm still house painting.  I do have a spare 75 750F engine which I can use for a clutch model if necessary, just can't get to it for a while. It will tell what NOT to do in a later basket.

What parts did you order and from where? BikeBandit maybe, considering the non-Honda part numbers you posted. How about converting the numbers to Honda numbers like Mec posted? Link us to your parts page you are using too.

Which basket do you have? Shorter earlier one or longer later one?

[stueveone]

Hey Jerry,
Right, the mainshaft (see photo) has the groove for the circlip and sticks out further, which is indicative of the later model mainshaft/clutch assembly, which is why I was figuring it was from the k6-8 version.
I purchased an entire clutch assembly from eBay that had all of the missing pieces listed in my previous post. We shall see and I will surely keep you updated!

[Jerry Rxman Griffin aka MuthaF'er]

Mainshaft has the same part number for all the bikes. Dammit I really gotta quit playing with this and get back to home restoration 

[stueveone]

You're right, same freakin' part number!
Well, same part numbers or not, one of the mainshafts has a groove for a circlilp and one doesn't. So, I think we're still on the right path here. I'll know more once the parts arrive!

[Jerry Rxman Griffin aka MuthaF'er]

Hope it's a few days! I gotta get off this damned computer and paint some walls. Ladders await 

[lucky]

The transmission has two shafts.

Main shaft and counter shaft. The counter shaft has the countershaft sprocket that connects to the rear wheel.

the 750 has one more:
(according to my honda genuine parts list)
23210-300-000 shaft comp., main transmission
23220-300-010 shaft, counter, transmission
23520-300-305 shaft comp., final driven..........this is the one the sproket sits.

mec

You are right... I was just simplifying it all.

[stueveone]

Well... That was it!!!
Got all the parts rounded up over the last couple days and went at it.

Clutch basket:
As Jerry did an amazing job photo documenting the differences, the k6-8 clutch basket is longer (or taller, depending on how you are measuring it). This is to incorporate that funny dual steel disc that is located in the middle. So, if you have a later model mainshaft k6-8 in an earlier model engine and you don't have the matching k6-8 clutch basket and associated hardware; you will have to source the following parts:

1. clutch center part # 611690
2. Washer 726068
3. Circlip 727794
4. clutch outer 611690
5. friction disc B 612444
6. steel plate B 612542

The list above basically amounts to the newer style clutch basket and associated longer hub. The dual steel plates, 1 pinwheel outer friction plate, 1 circlip, and 1 smaller diameter thrust washer.

Modifying Clutch cover:
So, what I did was assemble the clutch with the springs and outer plate, just like how you would assemble it on the bike and then mated it with the corresponding piece that pushes the throwout bearing on the outer clutch cover. I then rotated the clutch assembly on the clutch cover where it would mate up normally to see how much material I would have to remove from the screw boss near the kick starter. What I found helpful was to lay the clutch cover down (engine side up), then lay the clutch basket on top how it would normally mate up, and look at it from the side to "sight" in where the clutch basket was resting on the screw boss. I then removed material from the screw boss with a hand file, enough so that when the clutch basket was resting on the now shaved screw boss, it was actually pitching up the opposite end, meaning that it was then clear when you square the 2 pieces up.
Am I over explaining this? Haha.
Anyways, check the photos for more info. And I got the damn thing going! Worked like a champ. Though, the liquid in my oil pressure gauge leaked out! What the hell?!!!

Hope all this helps,
stueve

[Jerry Rxman Griffin aka MuthaF'er]

Great news!

What site are you using for those non-standard part numbers? Can you translate your part numbers into actual Honda part numbers?

[stueveone]

I used bike bandit for the part numbers. None of those parts are available anymore (at least through BB). So they are only for reference!