Topic: Splitting the cases on my CB750...first of many ?'s

[ekpent]

Those are some big pieces,I am sure you will see where they came from. When your "new" stuff comes in and you start to put it back together if you need a tid bit or whatever give me a shout here in the Kazoo-shipping is cheap and next time in town look me up-    Eric

[ekpent]

Hey 754- Should he keep them DOGS in his own yard-------

[ron.cieri.313]

Clearly we have found the source of the problem...I pulled the main and countershafts...

2 dogs in their yard where they belong:


All 3 dogs off their chain:

[ron.cieri.313]

Oh yes, its the C5 gear  (the one closest to the outside of the bike...ty mystic)

[mystic_1]

Yeah, that'll affect your shifting just a bit!   

I'd strongly consider swapping in the entire replacement tranny if it is in good shape.  At the very least, consider replacing the gears that mate with the broken ones.

mystic_1

[MCRider]

DANG Dang Dang!  I ain't never seen nothin like that!

[HondaMan]

Me, neither. At least, not in a CB750 gearbox (or a 500, either). I've seen it in some 6-speed boxes and some more recent sportbikes, but not in the 750. 

The shock load to break a C5 gear like that had to either come from a chunk of something locking up the adjacent gear while the bike was moving at speed, I would estimate: it would take a lot of mass to do that!

[mystic_1]

Me, neither. At least, not in a CB750 gearbox (or a 500, either). I've seen it in some 6-speed boxes and some more recent sportbikes, but not in the 750. 

The shock load to break a C5 gear like that had to either come from a chunk of something locking up the adjacent gear while the bike was moving at speed, I would estimate: it would take a lot of mass to do that!

Looking back at the chipped teeth in post 59 of this thread, I'm thinking that's exactly what happened.

mystic_1

[ron.cieri.313]

Hmmm, way too unique for me unfortunately but I must "endeaver to perservere" (Outlaw Jose Wales).

So, I'm going to replace the whole tranny as suggested and waiting for it to arrive (already shipped)...I need to get the clutch off the main shaft...any tips?...can't see exactly where it ends and the mainshaft gear assembly begins.  I guess I will see more once the new/used assembly arrives but wouldn't mind getting started...thx.

[Henning]

I reckon the dogs got snapped off and debris from them got between the teeth, doing more damage.

So, Ron, what were you doing? Redlining it and dropping the clutch in second, or did you just miss a shift realllly badly?

[MCRider]

Hmmm, way too unique for me unfortunately but I must "endeaver to perservere" (Outlaw Jose Wales).

So, I'm going to replace the whole tranny as suggested and waiting for it to arrive (already shipped)...I need to get the clutch off the main shaft...any tips?...can't see exactly where it ends and the mainshaft gear assembly begins.  I guess I will see more once the new/used assembly arrives but wouldn't mind getting started...thx.

Remove the 4 bolts that hold the spring plate down. Do them a few turns each at a time as they are spring loaded and you want to avoid loading the plate unevenly. Then that plate comes off and the springs fall out. Then you'll see a "4 notch" nut with a lock tab holding it in place. Gonna be tough to loosen it with the shaft out of the bike. Maybe put it back in the cases and let the primary chains hold it from turning. May not be a good idea as you may dislodge the crank.

Anyway, gotta get it loose. Hammer and punch may do it. There is a 4 prong T handle tool, but you can't get much leverage with it. Some mechanics cut the 4 prong part off, weld it to an impact socket and use an air impact wrench. Once off the clutch hub comes out with the discs on it. Then the clutch basket and primary chain sprckts come off as an assy.

IIRC

[mystic_1]

Then you'll see a "4 notch" nut with a lock tab holding it in place. Gonna be tough to loosen it with the shaft out of the bike.

Gears are trashed anyway, clamp them in a vise!

mystic_1

[MCRider]

Then you'll see a "4 notch" nut with a lock tab holding it in place. Gonna be tough to loosen it with the shaft out of the bike.

Gears are trashed anyway, clamp them in a vise!

mystic_1

Eggselent point!

[754]

Yup lift out whole shaft, put in the vise, clamp shaft or gear, with aluminum pads.

 As soon as you have done all this, you will then realize why we told you to do this ..BEFORE splitting cases...


 If a single dog left the pack first, and a sliver jammed the gear, that may have broke the rest.. I was thinking...

[nobody]

Remove the 4 bolts that hold the spring plate down. Do them a few turns each at a time as they are spring loaded and you want to avoid loading the plate unevenly. Then that plate comes off and the springs fall out. Then you'll see a "4 notch" nut with a lock tab holding it in place. Gonna be tough to loosen it with the shaft out of the bike. Maybe put it back in the cases and let the primary chains hold it from turning. May not be a good idea as you may dislodge the crank.

Anyway, gotta get it loose. Hammer and punch may do it. There is a 4 prong T handle tool, but you can't get much leverage with it. Some mechanics cut the 4 prong part off, weld it to an impact socket and use an air impact wrench. Once off the clutch hub comes out with the discs on it. Then the clutch basket and primary chain sprckts come off as an assy.

I've still got a couple stubborn bolts holding my cases together. I tried to remove the clutch this way and by pinning the crank against the bench with a wrench, I can't seem to get the clutch to keep from spinning freely. Any ideas on how I can get the clutch off? Should I even worry about it if it worked fine prior to the breakdown?

[MCRider]

Remove the 4 bolts that hold the spring plate down. Do them a few turns each at a time as they are spring loaded and you want to avoid loading the plate unevenly. Then that plate comes off and the springs fall out. Then you'll see a "4 notch" nut with a lock tab holding it in place. Gonna be tough to loosen it with the shaft out of the bike. Maybe put it back in the cases and let the primary chains hold it from turning. May not be a good idea as you may dislodge the crank.

Anyway, gotta get it loose. Hammer and punch may do it. There is a 4 prong T handle tool, but you can't get much leverage with it. Some mechanics cut the 4 prong part off, weld it to an impact socket and use an air impact wrench. Once off the clutch hub comes out with the discs on it. Then the clutch basket and primary chain sprckts come off as an assy.

I've still got a couple stubborn bolts holding my cases together. I tried to remove the clutch this way and by pinning the crank against the bench with a wrench, I can't seem to get the clutch to keep from spinning freely. Any ideas on how I can get the clutch off? Should I even worry about it if it worked fine prior to the breakdown?

I'm not thinking straight. What i told you won't work. The crank doesn't hold the clutch center, just the outer. Gotta put it in gear and hold the output shaft.

And no, no absolute need to remove it if its not part of the fix.

[nobody]

Crap, well I already removed the gear selector and I'm pretty sure it's in neutral. I guess I'll just forget about it for now and see what happens when I get it all reassembled and back into the back. Don't fix what's not broken, right?

[MCRider]

Crap, well I already removed the gear selector and I'm pretty sure it's in neutral. I guess I'll just forget about it for now and see what happens when I get it all reassembled and back into the back. Don't fix what's not broken, right?

Yup.

sorry for the mis info.

[nobody]

No worries, no harm done.

[ron.cieri.313]

Question...do I need to remove the clutch innards (friction disc and such) prior to removing the clutch basket and sprockets which come off as an assembly?

...and H, yes, I'm sure I did something stupid but that really doesn't narrow it down for me ...I think it definitely happened though when i was attempting wot plug chops...ah well, i must be a masochist anyways otherwise why would I be doing this to begin with.

[MCRider]

Question...do I need to remove the clutch innards (friction disc and such) prior to removing the clutch basket and sprockets which come off as an assembly?

...and H, yes, I'm sure I did something stupid but that really doesn't narrow it down for me ...I think it definitely happened though when i was attempting wot plug chops...ah well, i must be a masochist anyways otherwise why would I be doing this to begin with.

I think you can, but under the circumstances you may want to remove all the plates and wipe them off, removing potential debris. Or have you already done tht?

[ron.cieri.313]

Yes, I mean I've rebuilt the clutch seriously like 5-6 using different configuations of metal plates and frictions disc...I was hoping the whole shifting issue was clutch related.

[MCRider]

Yes, I mean I've rebuilt the clutch seriously like 5-6 using different configuations of metal plates and frictions disc...I was hoping the whole shifting issue was clutch related.

Yes I remember now from earlier in the thread. So if the plates are clean, and you can pull them out together, i think so, then might as well.

Tho you may be an expert at reinstalling clutch plates by now. 

[ron.cieri.313]

Lol...yes I am...unfortunately I getting to be an expert on everything 'cept riding this beastie

[HondaNorway]

I'm extremely glad I stumbled upon this thread. I've got a 74 750k with a hard shifting issue with the engine ready to come out of the frame. I'll be watching/posting in this thread frequently.

I am also extremely glad too see this thread! I actually got a '74  myself, which I'm going to fix up this winter. I started today, and so far i have taken out the battery basket, airbox, and some electric components.

Some of the thing's I am planning to do is;

-take out the engine and sandblast it -> paint it
-fix a gear shifting issue (some times it goes in neutral when it's not supposed to (CLUTCH RELATED??)
-repaint all black details
-new chain
-+++

I will read this thread often!

-Stian