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Author Topic: CB750 K0 Fork Top Pics?  (Read 628 times)

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Offline Lucien Harpress

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CB750 K0 Fork Top Pics?
« on: January 17, 2024, 01:04:06 PM »
I'm in the process of attempting to put together a late 1970 CB750, and basically deciding how nit-picky I'm going to go about it.  I think the current project is going to try to find a set of period-correct front forks, with the ridge.  While I'm definitely keeping an eye on Marketplace and eBay, I've also got the crazy idea of turning down a set of K1/K2 fork lowers to match the earlier sets.

With that in mind, does anyone have any detail shots of the top profile lip of the K0 lowers?  Edge-on shots would be best, and measurements would be even better.

Obviously correct parts would be best, but I also see what they go for.  And if a trip to my machinist cost less than that, I'm not above modifying parts to fit.

Thanks in advance!
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-1970 CB750 K0
-1980 KZ1300
-1976 Yellow GL1000
-1965 CA77 "Dream"
-1997 Valkyrie
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Online 69cb750

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Re: CB750 K0 Fork Top Pics?
« Reply #1 on: January 17, 2024, 01:54:06 PM »
The fork seal and leg was bigger in 71.
If you machine a 71 leg to look like a 70 leg not much left to hold the seal.

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Offline Lucien Harpress

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Re: CB750 K0 Fork Top Pics?
« Reply #2 on: January 17, 2024, 04:33:19 PM »
Well, that is annoyingly disappointing.   :(  The more you know, I suppose.

Thanks for the info!
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-1970 CB750 K0
-1980 KZ1300
-1976 Yellow GL1000
-1965 CA77 "Dream"
-1997 Valkyrie
-1975 Velosolex

Offline Don R

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Re: CB750 K0 Fork Top Pics?
« Reply #3 on: January 17, 2024, 05:11:54 PM »
  I think the ridge is below the seal but after dinner I can take a side by side pic of early 70 and late 70 (71) fork tops.
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Offline Lucien Harpress

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Re: CB750 K0 Fork Top Pics?
« Reply #4 on: January 17, 2024, 05:24:02 PM »
Thanks.  If you can get a measurement of the width of the ridge, even a rough one, I can double-check the depth of the fork when I take it apart.  That way I'll know if it interferes with anything.
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-1970 CB750 K0
-1980 KZ1300
-1976 Yellow GL1000
-1965 CA77 "Dream"
-1997 Valkyrie
-1975 Velosolex

Offline Don R

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Re: CB750 K0 Fork Top Pics?
« Reply #5 on: January 18, 2024, 01:10:22 PM »
 Sorry, I didn't make it back out last night. I'm going now.
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Offline MauiK3

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Re: CB750 K0 Fork Top Pics?
« Reply #6 on: January 18, 2024, 01:39:52 PM »
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Offline Don R

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Re: CB750 K0 Fork Top Pics?
« Reply #7 on: January 18, 2024, 02:23:15 PM »
 This shows the depth of the seal area, the OD is difficult to show. The tapered fork is for sure bigger everywhere. I think you could make a fooler fork but it won't be the real deal. The OD step would need to be lower than K0. do it and show me how it worked.
« Last Edit: January 18, 2024, 03:13:55 PM by Don R »
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Offline BenelliSEI

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Re: CB750 K0 Fork Top Pics?
« Reply #8 on: January 18, 2024, 03:47:52 PM »
Here’s a decent photo of mine. As you’re unlikely to park next to another one, ridden by a suspicious guy, with a set of calipers in his back pocket, should work?
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Offline Lucien Harpress

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Re: CB750 K0 Fork Top Pics?
« Reply #9 on: January 18, 2024, 04:25:42 PM »
Thanks for the side-by-side comparison.  The later forks are actually quite a bit more substantial in comparison than I was expecting.  I guess I realized that the later forks ran bigger seals, but I didn't realize pretty much every dimension was larger.

It's definitely got me thinking about what I want to do now.  Getting them turned down is a lot of work for something that will still be... 10% bigger?

Might be I keep running the K1 forks I've got and hold out until the real deal shows up again.   ;)

Thanks for the info!  It's been enlightening, for sure.
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-1970 CB750 K0
-1980 KZ1300
-1976 Yellow GL1000
-1965 CA77 "Dream"
-1997 Valkyrie
-1975 Velosolex

Offline Don R

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Re: CB750 K0 Fork Top Pics?
« Reply #10 on: January 18, 2024, 09:36:06 PM »
  Edited:
 The early top forks went to serial number 1039120 then a lot of parts changed numbers, but they have the same size seals and snap rings. Partzilla shows 35x46x11 mm seals for K0 and K1, that's incorrect. There is a fork top that's clearly K0 but slightly tapered, these may have been the last of the forks with the small 46mm seal.
  The cmsnl parts fische says Honda went to the big 48mm seals starting at 1044649 (K1)  That would mean my late number (43000 era) K0 has incorrect K1 forks.  Fudge, except I have a set ready to go on it.
  Does any of this make sense?
« Last Edit: January 18, 2024, 11:45:42 PM by Don R »
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Online 69cb750

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Re: CB750 K0 Fork Top Pics?
« Reply #11 on: January 19, 2024, 06:30:09 AM »
Quote
The early top forks went to serial number 1039120 then a lot of parts changed numbers
1st fork leg went to CB750-1039119
2nd fork leg from CB750-1039120 to CB750-1121806
The K1 fork leg was used on 5500 K0 bikes built in June 1970
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Offline Lucien Harpress

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Re: CB750 K0 Fork Top Pics?
« Reply #12 on: January 19, 2024, 06:51:50 AM »
...and guess who's frame got built in May?   ;D  ::)

Part of me hoped my frame was late enough that the later K1 forks would be correct, but looks like no dice.
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-1970 CB750 K0
-1980 KZ1300
-1976 Yellow GL1000
-1965 CA77 "Dream"
-1997 Valkyrie
-1975 Velosolex

Online 69cb750

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Re: CB750 K0 Fork Top Pics?
« Reply #13 on: January 19, 2024, 08:04:22 AM »
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Offline Don R

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Re: CB750 K0 Fork Top Pics?
« Reply #14 on: January 19, 2024, 08:31:26 AM »
Quote from: 69cb750 on January 19, 2024, 06:30:09 AM
Quote
The early top forks went to serial number 1039120 then a lot of parts changed numbers
1st fork leg went to CB750-1039119
2nd fork leg from CB750-1039120 to CB750-1121806
The K1 fork leg was used on 5500 K0 bikes built in June 1970

 OK then, mine is a June 70 bike so maybe it is correct.
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No matter how many times you paint over a shadow, it's still there.
 CEO at the no kill motorcycle shop.
 You don't need a weatherman to know which way the wind blows.

Offline Lucien Harpress

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Re: CB750 K0 Fork Top Pics?
« Reply #15 on: January 19, 2024, 09:08:56 AM »
Quote from: 69cb750 on January 19, 2024, 08:04:22 AM
1970 CB750 fork legs - https://www.ebay.com/itm/176175374887

That must have JUST got listed.  Thanks!
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-1970 CB750 K0
-1980 KZ1300
-1976 Yellow GL1000
-1965 CA77 "Dream"
-1997 Valkyrie
-1975 Velosolex
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