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Discussion Starter #1
Hello all,

New poster here but this website has been a great source of information! So first, thank you!

Guess I'll start with the questions:
- When all gears are in place, should I expect to be able to move the shift forks around by turning the drum by hand?
- Has anybody had success with straightening a shift fork maybe using a hydraulic press? is there any service out there that I could contact for that ?
- Anybody know where I could find a left shift fork for a CB450k3 (part number 24221292020). I contacted Ohio Cycles but they just sold them last week :(
- In case I manage to put that thing back together, are there any tests that I should do to see if my transmission is ok. Right now I have (both tests are done while simulating the engine rotation):
- turn the drum by hand with all the gears in place and see that the forks move without effort
- once the entire case is back together, check that the shifter pawl is placed correctly (which I did not do the first time and caused my doom)
Anything else I should check for?

Thank you very much for your help!

And here is the long story with pictures:

I bought a non working 1970 CB450 a year ago. More or less my first bike so I think I was not as kind with the clutch as I should have been when I first rode it... and after some time, the bike would not switch up from 1st gear.
When opening it, we realized that the left shift fork was bent and that because the knob supposed to constrain the shifter pawl movement was broken...

The missing knob:
Missing knob.jpg

The right shift fork showed little abrasion, whereas the left shift fork was bent and damaged.

Left:
Original Left Shift Fork.jpg

Right:
Original Right Shift Fork.jpg

Bent:
Original Left Shift Fork 2.jpg

This made it impossible to move the forks by hand
So obviously, because I didn't read this post https://www.hondatwins.net/forums/55-engine-discussion/31317-cb450-transmission-reassembly-help-bill-lane-steve.html, I bought a new $99 left shift fork on ebay and replaced it. That solved the issue for a while, but now the 2nd gear was slipping. Re-opened it, and the replaced shift fork is even worse than the first one, either because I did not put it back correctly or because the shifter pawl was bent... Probably both.

New shift fork:
Replacement.jpg
Replacement 2.jpg

So now, I have 2 bent / damaged shift forks. And I am not sure what to do with it... I already found a replacement shifter pawl but I am not sure how to proceed.
 

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You will have to fix that missing knob somehow, but a good welder could do it.
You need to be really careful about the orientation of the little clips that hold the shift fork pin-thingies in place. If one s\is backwards, problems ensue.
Did you take the whole tranny apart? There are some thrust washers that need to be correct, or things like this happen.
Always reassemble with things in the neutral position - test turn like you describe. Make sure it's still in neutral when you put the bottom case back on.
Test again.
What shape is your pizza cutter roller in?
 

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Discussion Starter #3
Did you take the whole tranny apart? There are some thrust washers that need to be correct, or things like this happen.
I took everything apart indeed... I put everything back together using a combination of photos I took and schematics like that one https://images.cmsnl.com/img/partslists/honda-cb450k3-usa-e-15-gear-shift-drum-shift-fork_big3IMG01171585_9100.gif

What shape is your pizza cutter roller in?
Is that a technical term :) ? Pizza cutter roller looks like it's in good shape... Should I be looking for specific damage?

Thanks for the advice!
 

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If there are marks on any of the other forks sides they are bent
Check shift drum for flattened points where the forks travel
Rotate trans while shifting to test

Sent from my SM-J320V using Tapatalk
 

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Discussion Starter #7
@Ancientdad, all introduced! Sorry I didn't do that earlier. Although I can not add a signature yet. I'll guess it comes with seniority.

Here are some more pictures of the rollers and 2 forks. Everything looks fine from what I can tell (except the forks). The rusty one is the newest one. It looks slightly less bent than the original one. Which makes sense since I can rotate the drum just fine with all gears in place with it. I am now wondering if it is ok to have use an obviously grounded fork...

The problem I had with that one was that the 2nd gear was slipping, and the travel between neutral and second gear felt really short if that makes sense. As in it was really really easy to miss. I am not sure how much of that can be attributed to the missing stop knob, the bent shifter pawl in the case and/or the over extended shifter pawl spring (#3 in there https://images.cmsnl.com/img/partslists/honda-cb450k3-usa-e-16-gear-shift-and-kick-starter-spindles_big3IMG01171586_d899.gif).

Here are the photos:

IMG_20181217_193610.jpg IMG_20181217_193616.jpg IMG_20181217_193620.jpg IMG_20181217_194043.jpg
IMG_20181217_193944.jpg IMG_20181217_193949.jpg
IMG_20181217_194132.jpg IMG_20181217_194235.jpg IMG_20181217_194256.jpg

Thanks for all the advice,
G
CB450K3
 

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Well, the shift forks are shot and need to be replaced, as already mentioned - even if the rub marks on the sides weren't nearly as bad as yours (and they're as bad as any I've seen), they would still need to be replaced. As for the pizza cutter... grab the roller on the arm and check the slop in the shaft and hole in the roller - it should be a snug fit that only rotates, no radial movement. The problem is that those parts are no longer available (NLA) and as such, good used ones are very hard to find so if yours is worn, it will need to be replaced or most likely repaired. And as also mentioned above, check the shift drum for wear on the points of the grooves where the shift fork pins move to see if any of the points are worn or flattened, as well as the engagement dogs on all of the gears considering how bad the forks look. And check the pins in the end of the shift drum too for wear, as well as the star points on the detent part the pins go in

As for your signature, it will be available for you to create after your 10th post... helps keep spammers down.
 

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Discussion Starter #10
grab the roller on the arm and check the slop in the shaft and hole in the roller
There is indeed radial movement in the pizza roller :/

check the shift drum for wear on the points of the grooves where the shift fork pins move to see if any of the points are worn or flattened, as well as the engagement dogs on all of the gears
All these look fine... There is no sign of dents or distortion in the drum grooves (see photo) and the engagement dogs don't have any damage on them. I have the exact same issue described by https://www.hondatwins.net/forums/55-engine-discussion/31317-cb450-transmission-reassembly-help-bill-lane-steve.html. Could this just come from the bent shifter pawl and radial pizza roller movement ? As in the drum was not fully rotated for the second gear, leading the disingagement + extra tension on the fork.

Also you mentioned repairs? I would one go and repair something like that? Could you recommend anybody?

The spring is clearly overextended (I'm already replacing that).


I recommended via PM that the OP replace the entire transmission, as a set
That would be great! but your private inbox is full :) I can't reply any more :/
 

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This is one of the things Tom was talking about - the "lumps" that the pizza cutter ride on in the end of the shift drum can actually get grooves worn in over time - that, combined with a wobbly pizza cutter, is the kiss of death.
In this photo there is very little wear there, but I've seen them deeply grooved.
This, along with the oil pump, are the two main design fails on the CB450.
 

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This is one of the things Tom was talking about - the "lumps" that the pizza cutter ride on in the end of the shift drum can actually get grooves worn in over time - that, combined with a wobbly pizza cutter, is the kiss of death.
In this photo there is very little wear there, but I've seen them deeply grooved.
This, along with the oil pump, are the two main design fails on the CB450.
Good picture Bill - I should have taken a few of mine while it was off. Hard to remember to take pics of every part while you're scheming the reassembly... :D
 

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Discussion Starter #15
Thanks for the awesome picture!
No deep groove of death where the pizza cutter would be :) but the radial movement is worry some and probably influences bad gear placement. I'll look into replacing that too.

HT member Tools1 can do it for you, he does a lot of machine work for members
I'll hit him up! Thanks!
 

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Thanks for the awesome picture!
No deep groove of death where the pizza cutter would be :) but the radial movement is worry some and probably influences bad gear placement. I'll look into replacing that too.


I'll hit him up! Thanks!
That "star-wheel" thing is almost impossible to find now. I think I bought (for a spare) what was probably the last new one on the planet, some years ago.
You'll have to pry it out of my cold, dead hands.
 

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Also, pay close attention to the thrust washers on the countershaft.
They have to be rotated to lock in place, or the transmission will pretty much self-destruct.
 

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Ok! So I found a used transmission on eBay but the pizza roller it came with also had radial movement.

I sorta managed to fix it? I noticed the rivets on the two rollers were protruding with a different height. So I added a washer of just the right size and put the entire thing in a wise grip (see photos). It looks like it got rid of the radial movement for now.. any idea of how long it will last? I guess it'd be better if I could put that in a hydraulic press instead of the wise grip. Any better idea? I'll install the new transmission tomorrow and see how it does.

IMG_20181220_123032.jpg IMG_20181220_123035.jpg
 
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