Author Topic: K0 gearshift drum swap Q?  (Read 342 times)

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Offline Don R

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K0 gearshift drum swap Q?
« on: February 13, 2024, 02:18:54 PM »
 Can the early, K0 style narrow groove shift drum be swapped for a later upgraded shift drum with the wider grooves, and are the shift forks different? 
 It appears that partzilla lists the cb750K through K6 having the same shift fork part numbers.
« Last Edit: February 13, 2024, 02:25:54 PM by Don R »
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Offline bryanj

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Re: K0 gearshift drum swap Q?
« Reply #1 on: February 13, 2024, 02:45:59 PM »
There is a bulletin about the later drum somewhere, i seem to remember the slot is the same, its the flat spot on top of the peaks that is wider.
I have posted the bulletin recently
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Offline HondaMan

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Re: K0 gearshift drum swap Q?
« Reply #2 on: February 13, 2024, 06:59:40 PM »
You can use the later shift drum in the early 750, but not always vice-versa. The pins on the shift forks got longer in the K4, while the grooves in the shift drum got deeper in the late K2. The early drum's shift grooves can sometimes then drag on the longer pins' edges in the later forks, requiring some filing/grinding to shorten them a little bit. It's do-able in a pinch.

But, using the later shift drum in the early engines always fits. It has one distinct characteristic that made me do it in my early K2: the Neutral 'bump' is wider and makes it easier to find Neutral, although if you're going racing it also slows the 1-2 shift a little bit as it makes the lever 'feel' heavier if trying to shift it quickly. I swapped mine at 121k miles because my Neutral Bump was getting worn and this would let it slip past Neutral easily when going from 2-to-N while rolling to a stop. For me it was an overall 'win'.
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Offline bryanj

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Re: K0 gearshift drum swap Q?
« Reply #3 on: February 13, 2024, 07:48:17 PM »
Bulletin
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Offline Don R

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Re: K0 gearshift drum swap Q?
« Reply #4 on: February 13, 2024, 10:27:14 PM »
 Thanks, believe it or not I did search for #40 bulletin. I'll try to get a picture of these two side by side. Who knows maybe it's an optical illusion, but I thought one was significantly wider than the other one. That bump is where it hangs up when I test shift it. There's a good chance they are both early type.
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