Topic: Gear selector assembly

[screwtheman]

I did the requisite 3 searches and didn't come up with an exact answer to my question.

I've got the tranny together. After looking at lots of photos and diagrams (no documents that  I have gave a detailed written description on assembling the selector mechanism), I finally figured out the gear selector assembly. But I'm not confident it's correct. The only people that will probably understand what I'm talking about have prior (and intimate) experience with the transmission assembly...

There are 5 pins that go into the shift drum. 4 of them are the same length and one is slightly shorter. Looking at the holes in the  back of the selector cam (thingy that has the neutral notch cut out of it), it's obvious that one of the pins doesn't pass through the shift stopper guide plate and into the cam. So you'd think it would be the shorter pin of the 5, right? Except the hole for the pin that doesn't pass through is so deep that even a long pin wouldn't reach the stopper guide plate.

I just want to double check that the short pin should indeed go in that hole.

I'm testing it out by rotating the clutch by hand and trying to shift through the gears. It's not easily going through all the gears (going into 1st, N, and 2nd are fine) and I'm suspect of the shift selector (bike shifted fine before disassembly). Any confirmation or advice is appreciated!

[Quail "Owner of the comfortable k8"]

I had a problem getting in into 3 4 5 and I loosened the cover screws and it worked fine, foun no gasket was used when it went together, I still have not figured out why it worked.

[screwtheman]

I found the sweet spot where everything lines up and I can upshift/downshift easily by hand without rotating the clutch. I compared the fork movement with the shop manual and they are moving correctly. So now the problem is after shifting into 3rd, the next catch pin on the drum is just barely out of reach from the shift linkage. It's so close that it rubs against it, but it isn't rotated around enough to catch. I ran out of steam and couldn't concentrate on it any longer.  I'll take another stab at it tomorrow.

Any ideas?

Oh, and I'd still like confirmation on the long/short pin thing 

[screwtheman]

BTT because I know there are some smarty pants here.

Where's Chung, MRieck, Bryan Jones when you need 'em??

UPDATE: So I got it shifting through all the gears. Sounds great, right? Well, when it's shifted into 3rd, the top countershaft "jumps" every revolution. I also notice the bearing carrier that mounts behind the shift linkage wasn't tightened all the way down. So I tightened it up pretty good and now it won't shift out of 2nd AT ALL. GRRRR. I've got the feeling I need to suck it up, disassemble the whole shebang and give it another go with my newfound understanding.

[screwtheman]

OK. I took the whole rigamarole apart this morning and I'm pretty sure I had the L & R shift forks switched  Once I stuck it all back together for what must be the 100th time, I lined up all the dogs (so I could test shifting), I could run through all the gears pretty easily! I feel pretty well educated on the CB750 transmission now. I hope it the most complicated part of the rebuild.

Thanks for everyone's help in this matter. 

[MRieck]

 Sorry about that but I just read your post- glad you figured it out! I have found the best source for detailed assembly are microfiches. You can usually see orientation of parts i.e. shift forks , and the correct order i.e. shifter mechanism with its multple springs and stepped spacers. Good for you for stepping back and reapproaching the problem- sometimes you have to walk away and ponder.

[screwtheman]

Hey! Someone does care! Ha ha! I think my post just kept getting bumped down to fast. No worries. I'd much rather figure stuff out on my own and this will hopefully help someone else out in the long run.

There's one last little nagging thing... Sometimes when rotating the countershaft (or magneto rotor) by hand and shifting by hand, it will roll smoothly and then suddenly the counter shaft will "jump up" as if two gears aren't meshing properly. I couldn't see any gears binding up. Plus it's weird that it rolls smoothly for a half rotation or so. So I tried running all through all the gears to see which ones were the problem ones and it was inconsistent (3rd may have jumped last time, but it's smooth as glass this time). I quadruple checked both shafts against my parts manual and shop manual to verify the gears all in their proper place. 

My only explanation is that this will not happen when the engine is actually running much faster than I can turn it, the case halves are cinched down, and everything is floating in oil. But I'm not real comfortable with that explanation. I can just imagine getting the motor together and running, then shifting into gear and hearing a heartbreaking "clunk" or "grrrrind". Any insight?

[MRieck]

 You have lost me on the countershaft/magneto rotor BUT yes..under running conditions it is alot different. Spinning the driven, or countershaft, will give you indication as to whether or not your assembly is basically right....don't expect it to be like running conditions. It sounds like you don't even have the case halves torqued yet! You got the forks right which, of course, is key.  don't fret to much....you'll drive yourself crazy! If you have followed the manual and it basically works on the bench OK. Put the caes halves together and than run through the gears - it won't be perefect but you should be able to upshift to 5th OK when spinning the coutershaft. Much more modern transmissions work better on the bench but that is because gear style is much better and 6 speed transmissions don't have to have the forks move such a great distance to engage gears. The CB transmission basically sucks compared to anything fron the last 15 to 17 years. If you undercut it and switch to a 77 or 78 clutch set up it is not too bad. Even with those mods, which I have, it is still funky from time to time. I think you have done a good job and it will be great.

[screwtheman]

Oops. I just meant I was spinning the generator rotor (and hence the crank and transmission) by hand while I was testing the shifting. Yes, I'm still doing all the work within the open lower case and I'm pretty sure that will make a difference once I finally get it cinched up. But it makes me feel better than someone agrees that it's a reasonable theory. Don't worry, I'm not hemming and hawing- I've got to get this bad boy together! 

Thank you very much!