Topic: "One. More. Time!"

[Dr. Frankenstein]

Yes, it does - but in the pics I took of the shifter mechanism before I took it apart (so I'd know how to put it all back together again), shows that plate covers a hole located in approximately the 9 o'clock position to the left of that plate - in other pics I have seen of the right side of the case that hole is partially covered by that plate as well -  but in the diagram it shows two screws (part #85) that appear to go into those holes - but with two screws in that plate, the plate itself won't lay flat against the edge of the drum face. Is it in there wrong??  (The 'missing' parts here aren't missing, I was just taking pics as I took this side apart so I'd know where everything goes). In this pic you can see the orientation of the plate, with that empty screw hole; my finger is simply holding down that shaft. I remember thinking at the time that empty screw hole was pretty peculiar.

But looking at it now, is that plate on backwards?? (Doesn't look like it, although I guess it could be...) ...and my 'part #33' does not look like the diagrams' Part #33 - there are not two screw-holes in that plate as shown in the diagram...let me guess: Honda made slight changes to parts without telling anybody...?

[HondaMan]

That threaded hole in the shaft by your finger is intended to let you install a (long) screw to pull it out when disassembling. Sometimes they get stuck if engines are sorely neglected.

But, this picture might be bringing up a clue: it looks like, during disassembly, the shift drum's pins and cover were removed. This frequently leads to less-than-best reassembly, because if the cover was reinstalled and the screw in it has worked loose even 1/4 turn, the shift drum has a real hard time trying to shift the gears. The reason is the precision of the grooves in the drum that move the forks to and fro: they are only allowed 0.1mm/0.004" of 'error' before the 2 gears that are both being moved by that shift can trip over each other's dogs-and-slots.

So, if yo have occasion to go back inside, look closely at how tight the screw is (or isn't) and how firmly held the tiny pins are by the cover on the shift drum. They must be tight.

[Dr. Frankenstein]

Okay, seems simple enough to tighten them down - but in that case I probably/hopefully won't have to split the cases again? Could that also be the reason the neutral switch was moving a bit in the video?

[HondaMan]

I just now got to watch that video: I see the wiggling Neutral Switch!
That IS odd. It indicates that somewhere in the tranny, some gear's dogs are clicking across the neighboring gears' slots, being too close to each other for Neutral to happen.

When this happens in the CB750 (most commonly 2nd gear) it is due to a bent "L" shift fork, which happens when the bike falls over to the left and something hits the shifter, pushing it upward without the engine running. Then the weight of the bike on the shifter arm screws the shift drum into the "L" forks' dog and moves the C2 gear hard against the C5 gear: without the engine running the dogs don't find slots and the sheer weight of the bike bends the shift fork tines sideways, moving the C2 gear off its normal disengaged position when not being used.

While this happens much more rarely on the lighter CB500/550, it does happen, and there will be a witness mark on the upper side of the tunnel where the shift shaft enters the engine below the drive sprocket. Sometimes the shift shaft gets bent slightly upward, too. This then puts a 'bias' against the shift drum, turning it slightly when in the unused position. That can sometimes cause the shift drum to turn ever-so-slightly off the "in between gears" Neutral position, which nudges gears C1 and M1 toward their neighbors in the gearbox. Then they 'click' against one another when the engine turns.

So, maybe put on the Sherlock Holmes hat & find a pipe to chew on (don't smoke around gas! I've done that...) and look for clues on the shifter arm, its shaft, or even on the (internal) shift arm ratchet parts to see if something is bent that is nudging the gears away from their Neutral positions. Inside the transmission, the tips of the dogs on a gear are tapping against the neighboring gear because the shift drum is not exactly in the Neutral spot. Something in the shift mechanism would be my best guess?

[Dr. Frankenstein]

It's in Neutral now - I was able to manipulate the shifter while spinning the wheel and it found Neutral, and that thumping noise in the video has gone away and everything rotates smoothly so I'm thinking the pins are in the drum valleys where they should be  - but I'm thinking I'll start with making sure that drum screw is tight and see if that makes a difference.

FWIW I did not notice anything bent or seemingly damaged when I took it apart, esp. with the shift shaft. I have previously had some experience working on a couple Dreams, and one of them had a very slightly, almost unnoticeable bent shift shaft that was screwing with the shaft seal - drove me nuts until I took it out and looked at it - so I 'm kind of careful in that respect. I'll start with tightening the drum screw and see what happens; I really don't want to have to open it up again, but it certainly won't fix itself if that doesn't work.

UPDATE: I went out and took off the side cover and removed the clutch so I could see what the shift drum is doing, so I tightened the bolts (didn't need it, but I snugged them up anyway - they didn't move), and messing with the shifter I did get it into and out of Neutral a few times to where it wasn't making any noise; currently I seem to have it between the gears again since it's making that noise again - But! I noticed that the little neutral switch brass sensor strip is currently at the 3 o'clock position, and while shifting though the gears I can't get it to align with the pickup sensor, which resides at around the 8 o'clock position.

The manual doesn't say anything about putting the drum in upside down, but is that possible? Shouldn't that pickup be resting on the neutral switch brass strip when it's in Neutral? Before I/we got into this procedure here, the Neutral dash light was lighting when it was in neutral - currently though I'm hunting all over the place trying to get it back to a Neutral position where it doesn't make that noise.   At this point I'm pretty much resigned to having to split her open again.

[bryanj]

No you cant fit the drum wrong but there is a tiny pip on the back of the neutral switch rotor that fits in a groove in the drum spigot, this frequently gets broken off and the rotor ends up in the wrong place so the light comes on when it aint in neutral

[Dr. Frankenstein]

Nope - that's there too. I'm just trying to decide if I need to open this thing up again. So after a night's sleep while my brain percolated on this problem, would a 'new' drum and forks fix it? I have new rings on the way for it anyway, so I'm probably going to open her up again and might as well replace the forks and see what happens. What years are compatible with the '74 CB550K0? (The bike's ID plate says it's a 73, but 'whatever.')

Just for speculation, here's a pic of the C2 shift fork when I had the engine apart the first time - after consulting the forum, I ground that rough semi-circle spot smooth and it seemed to me there was enough tooth left on the fork itself, but that being the Center shift fork, could that be responsible for the sloppy shifting?  And another pic of the transmission with some possible wear areas that might yield a few more clues; and a pic of the odometer on the bike - I've never seen one with that much mileage on it, but if that's accurate, that's a lot of wear, I would think...
   

[Kelly E]

What years are compatible with the '74 CB550K0? (The bike's ID plate says it's a 73, but 'whatever.')
 

My 74' CB 550K0 has a build date of 6/73 and the serial number is CB550-1000449.

[Don R]

 Does the Honda manual give wear limits for those parts?

[HondaMan]

I remember when Crazy PJ posted on his rollover to 100,000 miles with his 550!
He never mentioned any problems like this with his, though.
The drum itself rotates a little over 320 degrees from 1st to 5th gear. I can't think of a way that it could be upside-down? I don't think the C fork would allow that, even all by itself.
When you shift it into 1st gear and then half-shift it back to Neutral, where is the raised portion of the Neutral Switch's Cam pointed?

[Dr. Frankenstein]

"When you shift it into 1st gear and then half-shift it back to Neutral, where is the raised portion of the Neutral Switch's Cam pointed?"
 
By the 'raised' portion, I assume you mean the little brass sensor strip...? It's just slightly above the 3 0'clock position. It may be worth noting that the little nub on the back IS in its slot.

[Little_Phil]

In neutral the brass should obviously contact the fixed brass contact that has the LG/R wire that is about 150 deg CW further round. Are you sure this is neutral and not some false neutral between gears?

[Dr. Frankenstein]

Pretty sure; this seems to be the neutral spot above 1st gear - - and I agree: in Neutral, shouldn't that little brass spot on the cam there be meeting the little forked sensor? But it's not; that's one of the things I'm trying to figure out - if you can't put the drum in backwards or upside down, why isn't that sensor meeting the forks on the wire? There's no 'correct' way to put the drum back in, all it says is to make sure you have the forks in the right order when you put the drum back in, which I have done. And all it says regarding the neutral switch is to "align the neutral switch to the groove in the gear shift drum and lock in place with the 6mm screw."  It makes me think I slid the drum in 180 degrees out or something - but if you can't put it in wrong, wtf?

The shift forks looked fine except for the C2 (center) one, and I took some advice here on the forum and just smoothed out that rough wear mark on it as seen in the pic - but maybe that's the reason?

I'm probably just going to open it up again and do it over; I have new rings coming anyway, and once you get the head off it's a simple matter to go all the way and split the cases. It's not too bad of a job, but MAN that engine is heavy when it's just 'you'.   

While we're at it, does this gear setup look good? You can see the tips of the shift forks in their channels...

[HondaMan]

This is wild: it looks like the shift drum is 180 degrees flipped over!
I've never tried to do that...I wonder if it can be done?
You might be breaking new ground!

[Dr. Frankenstein]

If there is a way to screw it up, I will find it!  Actually, you may be right! I took the engine apart again today and rebuilt it, paying special attention to the position of the drum and neutral switch when I put it on. I actually DID rotate the drum before I put the C2 gear back on so the little notch would align with where the neutral sensor will be, and then I ran through the gears on the bench again, turning the shift drum by hand, and THIS time every time I went from 1st to Neutral the little brass pointer aligned with where the sensor will be.  I'm still working on it - I have the cases together, but the kick starter is acting weird...it seems to mesh with the first gear, making a ratcheting noise. I'll try to get a video of it up on YouTube. I thought the kick starter spring pushed the kick starter gear out of the way after you used it - I didn't take it out this time either, although IIRC I didn't do anything special to it the first time (and Second) I rebuilt it...??

That pic of the drum and forks was the previous time I rebuilt it, not this time.  Here's the video of the kick starter thing...https://youtube.com/shorts/qb7SakfNt6c?feature=share

[Little_Phil]

Have you got the KS return spring on and tensioned?

[MauiK3]

Very strange stuff here. Good to see you are getting closer

[Dr. Frankenstein]

Yes, the KS spring is on and tensioned - BUT! Good point - the kick starter itself is not on, so that may be a factor.

Yes, this has been a weird build so far.

[HondaMan]

Wow! I didn't know you could put the drum in 180 degrees out like that.
The kickstarter in the 500/550 is the biggest PITA in the engine. Be sure of one thing: make the rounded side of that circlip face the springs and washers. Otherwise it can pop off while kickstarting, and I won't tell you why I know that...

[Dr. Frankenstein]

Good to know, I'll check that; but I haven't touched the kick starter in all the times I've rebuilt this engine (3 now!). Note though I have followed the manual to the T and everything is in there how the manual says it should be, but I don't recall ever having any problems with it. The engine actually went back into the frame pretty easily with the help of a small jack to level things out, I was pleasantly surprised. Tore up the paint a little bit on the lower frame, but nothing a brush can't fix.

I have the bottom half back in with the cylinder head which went onto the engine in record time, but I had to step back - I had forgotten to put the rear wheel seal back in during all those problems I had with the retainer a few weeks ago and since I had the rear wheel already off I decided to put it in and - well - it got pretty mangled after getting snagged on the rough edges of the retainer, but I finally got it in and then found the hole was slightly out of round and I couldn't get the drive chain tensioner back on because the damaged seal was pushing the spacer off-center and cockeyed and it was 4:30 and nothing was behaving and I was getting good and pissed when the garage gods laid a gentle hand on my shoulder and said "Dude - Enough." You have to know when to walk away.

So "It's Miller Time!" as they say...I'll jump back on it in the morning.

[CycleRanger]

The garage gods are wise that way, I have felt their hand many times as well. 

[Dr. Frankenstein]

Oh, thank the Garage Gods! I thought it was just Me!