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Discussion Starter #1 (Edited)
I just took my case apart to inspect the tranny and replace parts as necessary. I noticed this wear mark in the case (from a gear) and also noted some abnormal wear on the adjacent shift fork. Is the shift fork bent a little? Is the wear caused by the shift fork? This is my first time in a 450 tranny but I’m familiar with the shift detent star and roller issues and that they can cause other shift fork problems. The bike did have an issue popping back into neutral from first and second.

Edit: here’s another photo of the shift fork in question:Is this wear too much and is the gear wear on the case a cause for concern?

 

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Lay the shafts and gears back in and run it thru by hand and see how much play there is and if the gears are rubbing the case. Looks to me like the shift forks need replaced. I would also check the area
that the forks ride in. Hard to tell with seeing it all.

Bill
 

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That fork in the second picture is bent, rub marks down in the throat. The gear should never touch there, only on the machined pads at the ends
.
 

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Discussion Starter #4 (Edited)
Ok cool. I have some replacement shift forks that I can swap out. As for the grooves where the forks ride, I deglazed them using some red scotch bright and they look nice and smooth. The next thing I need to address is the gear rubbing on the inside of the case. It hasn’t rubbed much. Maybe
.010” of an inch at most. It seems like the larger gears on the end of each shaft could have a little less slop. Like the washer that is right next to the large gears could be thicker. Is it common to shim these shafts for play?

 

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I've never shimmed a transmission shaft in any Honda trans ever. I'm sure the FSM has a spec for it but I've never encountered a situation where excess clearance was an issue. As for the gear lightly rubbing the case, the potential for a slightly bent shift fork on that end would cause not only the rub marks on the fork itself, but could have spaced the gear over toward the case enough for it to rub slightly at times. You should thoroughly inspect the engagement dogs and corresponding openings in the gears as well for any wear or rounding off of the dog ends or the machined holes for the dogs in the gears... if you replace the forks and not the gears worn in those areas, the forks will have undue stress on them again soon and the process will repeat itself. The fiche for the CB450K4 shows only one size and part number for the thrust washers, shown on each end of the two shafts beside the needle bearing caps, and from the look of your picture and the feeler gauge it might be missing, and might also explain the shift fork and gear wear along with the rub marks on the case #31 at the link below

https://www.cmsnl.com/honda-cb450k5-1972-usa_model453/partslist/E++14.html#results
 

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Discussion Starter #6
All thrust washers are in place. I’ve taken a look at all these gears and dogs here and everything actually looks really good except for the forks and that rub spot. Someone in the past has definitely been into this bottom end. As I was going through and shifting the tranny through all of its gears it seemed like that gear didn’t even come close to the side of the case so I’m wondering if that is an issue that was already addressed.


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please also inspect the engagement dogs (both gears) for rounding. if too round, it'll slip into gear easily but not stay reliably. has the transmission been slipping out of gear?

as to shimming, these gearsets will accept an amazing amount of clearance and still work. however, that doesn't make them correct or functionally reliable for a gazillion miles (at least!). I typically have to reshim at least one wheel gear as a line mech. so, follow the side clearance spec and shim accordingly on the wheel gears. then, review the shim bias so the dogs engage fully then update accordingly.

it sounds like a lot of work, and it is tedious but not hard and the upper case is set up so everything is pinned or circlip'd in position, Honda helped us with that design. the factory manual is pretty good for this.

good luck!
 

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sorry, didn't read (or comprehend, ha!) what you just wrote. so now, just ensure shim bias/dog engagement are good.
and, replace that bent fork, and any other that is worn through the chrome.
 
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Discussion Starter #9 (Edited)
Awesome sounds great!
I’ll take another good look at the engagement dogs and make sure i have the forks lined out that need replacement. These do seem a bit intimidating to get into but at the same time reassembly seems like it would be pretty strait forward. Especially with the parts diagram above to reference. Thanks!
 
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