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Looking at that assembly - and bearing in mind previous observations about poor design - I've curious as to whether there might be another way to put the assembly together. Since I don't have one of these things, I can't test the theory so bear with me. And you'll have to be a bit imaginatively creative 'cos I haven't got the bits and I'll have to describe what I'm taking about.

Looking at this image, I have a feeling the black end of the knob should pretty much sit against the outer mount, rather than standing off it - and it should be held there by the spring.

296208d1575685213-wanted-cb450k0-seat-spring-part-77203-283-010-img_3677.jpg

Humour me and give this a try:

- start with the assembly apart

- poke the pointy end of the knob through the outer mount hole

- turn the spring 180deg from its orientation in the picture and put it over the pointy end of the knob (inside the gap between the outer and inner mount holes) so the wide end sits flat against the inside of the outer mount hole

- thread the threaded washer onto the pointy end of the knob, with the spring set side facing the spring

Assembled like that, the spring will sit around the unthreaded end of the knob whilst pulling the assembly in towards the frame. It'll also reduce the chances of the seat coming undone by accident; the way it's set up in the pictures above is almost tempting fate to make it undo 'cos the spring is forcing the knob away from the frame rather than into it.

I may be way off, but I thought I'd chuck it out there based on experiences with other, similar age bikes coupled with the fact the knob seems to be standing off the housing a very long way. Incidentally, microfiche drawings aren't always the most accurate guides to assembly . . . ask me how I know.
 

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Looking at that assembly - and bearing in mind previous observations about poor design - I've curious as to whether there might be another way to put the assembly together. Since I don't have one of these things, I can't test the theory so bear with me. And you'll have to be a bit imaginatively creative 'cos I haven't got the bits and I'll have to describe what I'm taking about.

Looking at this image, I have a feeling the black end of the knob should pretty much sit against the outer mount, rather than standing off it - and it should be held there by the spring.
Ok, So I went ahead and gave this a shot. If I understand correctly, You want me to try putting together the latch assembly by placing the small side of the spring pointing away from the bolt instead of pointing towards the bolt. And then inserting the threaded washer on the small side of the spring (on the side of the spring furthest away from the bolt)?

basically, flip around parts 7 and 8
8336E38D-63AA-4190-964F-1451DF98EB44.jpeg

Before I go any further, I want to take a minute to explain that every image of the K0 Latch assembly I've found online has shown the small side of the spring pointing towards the bolt knob, with half the bolt being forced out of the assembly by the spring pressure...

IMG_3586.jpg IMG_3581.jpg IMG_3577.jpg IMG_3575.jpg IMG_3574.jpg

******Every image, BUT, this one....*******
IMG_3587.jpg

At first I considered the image too blurry to understand the arrangement of the assembly. However, now that you've made your suggestion I can see through the blur that, that is EXACTLY how the latch is assembled. Just Like you described it!

So When I tried it for myself all the pieces fit very nicely and the entire assembly seems much more rigid and secure.
IMG_3681.jpg

At this point I'm convinced that the original Honda engineer, in charge of the latch design, must have gone mysteriously missing mid design and the new engineer who replaced him instructed the line workers of the latch assembly's orientation incorrectly. You, the-chauffeur, are obviously his reincarnation.

Another interesting find about this arrangement.... Earlier I mentioned that part#8 in the parts manual looks nothing like the part#8 that i'm seeing on peoples bikes. I first tried the small threaded washer, the one meant to allow the bolt to float on the flat spot of the threads. Well, the small washer did not work out very well. Now that the spring is pushing the threaded washer towards the threads, instead of away, it keeps getting caught on the threads and unscrewing from the bolt when spinning the bolt as if you where unscrewing the seat from the frame. However, When I tried the larger threaded washer, The one that I did not trim down and looks much more like the actual part#8 in the parts manual everything worked out perfectly. It seems that if you tighten the larger washer to butt-up tightly against the backing of the bolt then the force of the spring holding the washer in place is not enough to make it unthread from the bolt. you can unscrew the bolt from the frame and the threaded washer spins freely inside the small end of the spring! Very nice.

the-chauffeur, I think you are 100% correct. This design is much better. I wonder why things where changed? Why part#8 was changed in design and installed with the bolt hanging away from the frame instead of being pushed in towards the frame. My only thought is that with the bolt now being pushed in towards the frame, and the mounting bracket being pushed slightly back, under the frame tube if you don't take care to pull the knob away from the frame as you lower the seat then you risk scratching the frame (not a big deal) or damaging the threads on the tip of the bolt (slightly bigger deal, but still not too bad). Interesting.

That was fun. Thank you for this.
-Isaias
 

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Hey, as long as you guys are in the "experimenting" mood, if one of you can provide the dimensions of the spring then I bet I can find one for a few bucks rather than $20 (I work for a huge spring manufacturer and I bet we make one just like it). Won't help you two since you both already have it, but might help someone else in the future!

If you can, can you provide the:
-inside diameter of the small end
-outside diameter of the large end
-length with no force on it
-is it magnetic?
 

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Hey, as long as you guys are in the "experimenting" mood, if one of you can provide the dimensions of the spring then I bet I can find one for a few bucks rather than $20 (I work for a huge spring manufacturer and I bet we make one just like it). Won't help you two since you both already have it, but might help someone else in the future!

If you can, can you provide the:
-inside diameter of the small end
-outside diameter of the large end
-length with no force on it
-is it magnetic?
I have an Old spring and a new spring. I'll provide dimensions for both.

New:
-inside diameter of the small end: 11.8mm
-outside diameter of the large end: 24.37mm
-length with no force on it: 30.71mm
-is it magnetic?: Not magnetic itself. Just plain steel. Is it attracted to a magnet, Yes.
-Diameter of wire: 1.25mm

Old:
-inside diameter of the small end: 12mm
-outside diameter of the large end: 23.95mm
-length with no force on it: 29.48mm
-is it magnetic?: Not magnetic itself. Just plain steel. Is it attracted to a magnet, Yes.
-Diameter of wire: 1.33mm

-Isaias
 

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Wow - that's pretty cool. Glad you like it.

The images you've got are a bit odd insofar as - as you say - there are so many of them that show the assembly back-to-front. That being said, it's hard to know whether any of the bits shown are from original, unmolested bikes; it's entirely possible the assemblies in the pictures have been disassembled in the past and put back together using the microfiche as a guide. As I think I mentioned, I've been caught out like that before and it's only through trial and error that you eventually come to realise that for a very small (but sometimes significant - like carb internals) proportion of any rebuild, the microfiche will be unreliable when it comes to assembly technique. I guess that's 'cos they were only intended to be parts lists, not build guides.

Your job may also be made a bit harder by some of the manuals from around that time having reused the microfiche images rather than photographing their own 'cos, well, cheaper I guess. So if the owner(s) of the bikes in those images have followed a Clymer manual, it's highly likely they came to the same conclusion you originally did because that's exactly what's shown.

To their great credit, Honda put a lot of R&D time into those early bikes; get them together right and you can really see how well they were designed.

Good luck with the rest of it.
 

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******Every image, BUT, this one....*******
View attachment 296350
Further proof that some of the stuff found on the internet is NOT always correct - excellent resolution, good on you Chauffeur :D (sure hope the new software brings back a thumbs-up emoji)
 

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Looking back at the microfiche diagram, something occurred to me about the design/layout . . .

. . . while it looks weird to us now, some bits were drawn back-to-front because if you tried to draw them the right way round, you'd miss a lot of detail and make them hard to identify/differentiate. Specifically, you'd only see the flat (back) side of part number 8, which to the casual observer would make it look like a funny shaped washer. At that time, parts manuals relied on line drawings from the perspective of the most advantageous viewing angle. If the illustrators had shown part 8 the "right" way round in relation to the knob, you wouldn't be able to see the extended threaded section because that bit would be obscured by the diameter of the flat end. As for the spring, the way it's drawn shows it's orientation in relation to part 8, rather than it's orientation in the context of the entire assembly.

Admittedly an explanation or even an arrow or two would make that whole diagram clearer, but I very much doubt Honda could have foreseen that anyone other than their techs would ever gain access to the parts diagrams; at the time they were drawn, they were only ever intended for in-house use by people who knew how the assemblies should be put together. They certainly couldn't have ever imagined that fifty years on from their manufacture their machines would be rebuilt by amateurs like you and me who have more-or-less instant access to all of the original parts diagrams via handheld/mobile devices . . . but who also lack the day-to-day experience to know instinctively whether the drawings are the right way round . . .
 

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Amazing level of effort by the guys on this thread. I wanted to share with you pics of my 20.00 spring that I bought via ebay. The spring will work fine but man do I feel financially violated...... : ) spring1.jpg spring2.jpg spring3.jpg
 

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Absolutely unacceptable! What delivery truck ran over the package? You should definitely send pics to the seller, this should be replaced with a functional spring. Please let us know how this turns out. If the seller isn’t willing to make this right then I would like to know who it is so I don’t make the mistake of ordering anything from them.
As far as this thread and it’s discoveries, I agree that it is excellent observations and quality experimentation to yield results that solve the mystery of why the seat latch seemed like such a crappy design by Honda standards. I only have one of these latches in my possession but it is assembled in the “wrong” floppy orientation like most of the photos posted. The solution offered by the Chauffeur makes perfect sense and I have to believe that is the way it was intended. With so many assembled “wrong” I have to think they came out of the factory this way for whatever reason. It is hard to tell if the one I have was ever disassembled but I can say that it came off of a seemingly unmolested bomber that sat untouched since the late 70’s. In fact the main problem I have now with this latch is that part #8 will not thread off the knob so I am unable to disassemble and finally make it work correctly. Further proof to me that it has always been assembled the way it is currently... “wrong”.
 

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In fact the main problem I have now with this latch is that part #8 will not thread off the knob so I am unable to disassemble and finally make it work correctly. Further proof to me that it has always been assembled the way it is currently... “wrong”.
I originally had the same problem with my assembly. Part#8 would not thread off the bolt. I had to take a M8x1.25 die to the threads of the Latch bolt to clean them up in order to get Part#8 to finally catch the threads and screw off. In truth, The bolt is not threaded to M8x1.25. I'm not sure to what Japanese standard the bolt is threaded too. But when using an original JIS Bolt and nut the fit if Very Very tight, almost a perfect fit. M8x1.25 is just slightly "looser" than the original JIS threading while at the same time still working with the JIS threads. So taking a M8x1.25 die to the threads just slightly repositions the threads while still leaving a functioning bolt.

The reproduction Latch bolt is threaded to the correct JIS thread size. So the Lowes M8x1.25 flanged nut will not fit without being FORCED on the very first time. But after that first time, once the threads have been re positioned, the fit should be just right.


Looking back at the microfiche diagram, something occurred to me about the design/layout . . .

. . . while it looks weird to us now, some bits were drawn back-to-front because if you tried to draw them the right way round, you'd miss a lot of detail and make them hard to identify/differentiate. Specifically, you'd only see the flat (back) side of part number 8, which to the casual observer would make it look like a funny shaped washer. At that time, parts manuals relied on line drawings from the perspective of the most advantageous viewing angle. If the illustrators had shown part 8 the "right" way round in relation to the knob, you wouldn't be able to see the extended threaded section because that bit would be obscured by the diameter of the flat end. As for the spring, the way it's drawn shows it's orientation in relation to part 8, rather than it's orientation in the context of the entire assembly.

Admittedly an explanation or even an arrow or two would make that whole diagram clearer, but I very much doubt Honda could have foreseen that anyone other than their techs would ever gain access to the parts diagrams; at the time they were drawn, they were only ever intended for in-house use by people who knew how the assemblies should be put together. They certainly couldn't have ever imagined that fifty years on from their manufacture their machines would be rebuilt by amateurs like you and me who have more-or-less instant access to all of the original parts diagrams via handheld/mobile devices . . . but who also lack the day-to-day experience to know instinctively whether the drawings are the right way round . . .
These are all very good points and frankly, something that never crossed my mine. I'll definitely be keeping this in mind during my build. Because, until now, the orientation of the parts in the manual where like scripture to me. Thank you!


Amazing level of effort by the guys on this thread. I wanted to share with you pics of my 20.00 spring that I bought via ebay. The spring will work fine but man do I feel financially violated...... : ) View attachment 296526 View attachment 296528 View attachment 296530
LMAO! :eek:, That SUCKS!!


-Isaias
 

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Sorry for sidetracking this conversation, but I'm going to geek out for a second here and be an engineer instead of a mechanic.

Based on your spring dimensions, I calculated the stiffness of the new spring you purchased to be 6.5 lb/in, and the old spring to be 8.5 lb/in. If anyone wanted to, I bet they can buy part # 1692K54 from McMaster Carr for $3 instead of spending $20: https://www.mcmaster.com/1692k54

The inside diameter of the small end is a tiny bit smaller but from your pictures it looks like you have some wiggle room there anyway.
 

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Curiosity has gotten the best of me. I don’t need the spring but I ordered one anyways. McMaster’s website does not advise you what S/H charges are, so I emailed them and they advised S/H would be about $7 to CA. That’s $10 a spring. A lot better than paying $20 a spring! And I’m sure if you bought in bulk it would increase the savings further :).

I’m looking forward to getting the spring in to compare to the Honda original. The more options we have for these rare parts the better I believe. Thanks.

-Isaias
 

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Based on your spring dimensions, I calculated the stiffness of the new spring you purchased to be 6.5 lb/in, and the old spring to be 8.5 lb/in. If anyone wanted to, I bet they can buy part # 1692K54 from McMaster Carr for $3 instead of spending $20: https://www.mcmaster.com/1692k54

The inside diameter of the small end is a tiny bit smaller but from your pictures it looks like you have some wiggle room there anyway.
The McMaster spring came in today (really fast shipping), and after some adjustments with a needle nose plier the spring looks to be a good substitute for the ridiculously priced Honda spring.

FA171496-DB2A-4301-8890-B92A1EFD58C7.jpeg

Here are the two springs side by side
BBFB815D-AB43-411D-8111-7CCF17DDFF99.jpeg 2D42F2D0-E899-4C93-BF3E-4676AE2A52B4.jpeg

And adjusting the “small” end to allow the threaded washer to fit
CB4A80D0-87F2-455D-83F3-E1F7D711A568.jpeg

Final sizing. I ended up making the McMaster springs “small” end just a hair larger than the threaded washers sleeve. This way the washer has less of a chance of getting caught up in the spring, but basically still approximate to the opening of the Honda spring.
5A8DD18D-2F8B-4ED4-9697-01BCB25501D4.jpeg

Full assembly. Pretty much exactly the same
1E85DA58-2887-4E00-BF74-36D8BB39B443.jpeg

I recommend the McMaster spring, especially at its price, over the Honda spring. The spring is noticeably not as strong as the Honda spring, but just by a small amount. If the McMaster spring providing 6lbs of pressure per sq inch then the Honda spring is probably only proving 9-10lbs. For its use I don’t believe that this plays a factor in the over all function.

Good find RenegadeZ3 and thanks for sharing the information.

-Isaias
 

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I recommend the McMaster spring, especially at its price, over the Honda spring. The spring is noticeably not as strong as the Honda spring, but just by a small amount. If the McMaster spring providing 6lbs of pressure per sq inch then the Honda spring is probably only proving 9-10lbs. For its use I don’t believe that this plays a factor in the over all function.

Good find RenegadeZ3 and thanks for sharing the information.

-Isaias
Glad it worked (even if it's only a small savings) and thanks for the update!
 
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