'76 clutch basket interchangeability

[viking91]

Hey everyone,
This is my first post and I'm looking for more information about clutch interchangeability between '75 and '76 sohcs. I have a 76 cb that I am trying to rebuild, but it came without a clutch (except for the outer basket). I have a clutch from a donor '75 motor but the plates don't appear to fit the 76 basket. Should I be able to put a clutch from a 75 into the 76 basket or can I buy a 75 basket and install it in my motor?

A related question has to do with testing the compression. The motor is not seized and the transmission/final drive is fine (I can shift between neutral and other gears). I can also rotate the kickstarter with the clutch basket out. However, if I put the outer clutch basket in, the kickstarter won't rotate (this is with no sparkplugs, so if its in neutral I believe this should rotate). Does this have something to do with the clutch being disengaged (ie the clutch not being in is the same has having the clutch lever in)? Will I have to fully install the clutch and "engage" it while in neutral to test the compression?

Thanks for the advice.

 

[cyclebuster]

I have never heard of either scenario. I have also never mixed clutches. But I do know that the CB750 has primary kick starting. The kick lever gear works directly upon the outer clutch basket, which is chained directly to the crank. The clutch has no effect on the kick starter. If your bike will kick with compression, in any form, the problem is in the transmission. can you put it in gear and roll it back and forth, and if so does the inner basket turn? It MUST be in neutral to kick start. you may have a false neutral. Or your transmission input is seized, somehow.
Email me Gary@cyclebusters.com
www.cyclebusters.com

 

[viking91]

I have the engine out of the frame right now so I can't tell if it rolls back and forth. What I can tell you is that when I turn the crank, the outer clutch basket turns with it, but not the final drive. I can also put it in gear and the transmission shaft will rotate with the final drive, but not the crank shaft. If I take the clutch basket out I can rotate the kickstarter, but when I put it in it won't turn (even if its in neutral or in gear).

My question is this: If the kickstarter is connected to the crank through the outer clutch basket, why can I turn the outer clutch through the crankshaft but not the other way around through the kickstarter? If the final drive is rotating independent of the transmission shaft and crankshaft, doesn't this mean it's in neutral? What do you mean by a false neutral?

By the way, thanks for responding so quickly I appreciate your input

 

[viking91]

Just a quick update, I just confirmed that it is not a false neutral, it will shift perfectly through all 5 gears and back to neutral. Another thing is that the shaft that the inner clutch basket is supposed to sit on does not rotate with the crank or the outer basket, but it does rotate with the final drive when in gear.

 

[cyclebuster]

does the engine kick over with compression with the clutch out?

 

[dirtdigger]

The 76 is the first year of a clutch similar to the later f1 motors and uses a different clutch basket then the 75. So do you have a 76 clutch basket or a 75 basket or both? Is it possible when you are installing the clutch basket you are not getting the gears meshed properly and it is binding?

 

[viking91]

No. If the whole outer clutch basket is out, the kickstarter is not connected to the crankshaft at. If just the outer clutch is in, the kickstarter won't rotate. Because of this I haven't been able to test the compression.

 

[viking91]

I am trying to use a 75 clutch with a 76 outer basket/motor. Is this possible?

 

[dirtdigger]

It seems to me something is seating right or something is binding with the gear on the basket. OK, the big gear for the kickstart turns fairly easily if the basket is out correct?

With the basket in the motor the big gear should still have just a little bit of wiggle. Normally you have to get the basket on the shaft splines then turn the kickstart gear a little bit to get the gear to mesh with the basket while pushing the basket to fully seat it on the shaft.

I think the innner is the same between the two but it should be fairly obvious if the pieces will mate together while trying to assemble it but you need to get the first problem solved first before getting the rest of the clutch together.

 

[viking91]

Yes, the large kickstarter gear rotates fine with the basket out. As soon as the basket is in the motor (with the basket gear meshed with the kickstarter gear) the kickstarter will not rotate. Does the whole clutch have to be assembled (and engaged) for the kickstarter to work properly?

 

[dirtdigger]

No, the basket is all that needs to be there. Does the kickstart shaft itself turn with the basket out....with some tension of course because it is spring loaded. I am talking about the shaft not the gear. The gear will free spin on the shaft until you start to turn the shaft, then the gear should lock to the gear.

 

[viking91]

Yes, the kickstarter shaft turns fine until the basket is put in, then it wont

 

[cyclebuster]

the outer basket cannot be removed. chains and lock rings keep it in place. there is no valid circumstance where the kickstarter does not work regardless of the condition of the clutches. if the clutch outer basket was welded solid to the inner hub drive shaft it would still work in neutral as normal. If you put the bike in gear and kick the bike over with the clutch lever out, the engine will roll, and the bike will move forward. IF you kick it with the lever in it will roll the engine only. I will go look at my 74 hub, its loose as the case is in halves. I am sure you cannot remove it without splitting the cases.

 

[dirtdigger]

If you put the basket on the shaft just started on the splines but not engaged on the gear can you turn the motor over? This is just a thought and I am sorry about all the questions....I am just wonder if you cant put enough weight on the kickstarter with the motor out of the bike to turn the motor over. There still is a fair amount of resistance even without the plugs when turning the motor over. Can you use the starter to turn the motor over?

 

[dirtdigger]

There are no chains holding the outer clutch basket into the motor.

 

[dirtdigger]

The outer clutch basket can most definitely be taken off the shaft without splitting the case, it is on the outside of the mainshaft bearing.

 

[viking91]

I can turn the motor over at the crank with fairly little resistance with a socket wrench, should the kickstarter require much more force than that?

 

[dirtdigger]

With the clutch basket in and seated can you still turn the motor over with your socket wrench? Yes it will turn harder by hand because you are working against the internal gear reduction of the crankshaft to the primary shaft.

 

[cyclebuster]

hmm I am gonna go get my hub, you may be right, are the kickstart gears the same size inside?

 

[viking91]

Yes, with the clutch basket in, I can easily rotate the crank with a wrench. Should I be able to rotate the kickstarter by hand with no spark plugs, or will I have to use a lot more force? I'm worried about applying to much force if something is wrong/binding and breaking something.