Speedo & Tacho Drives

[kp]

Hi Guys,
I have another topic that I don't know the answer to. We know that Honda fitted different speedo and tacho drives to the early CB750s. The early type is generally known as the sandcast or non-bevel type, not because it was only fitted to sandcast 750s but because it has a sandcast finish and was a cast item. The other type is commonly known as the die-cast or bevel type. Can anyone shed some light on what is the correct speedo/tacho type for what VIN range.
My unmolested non-sandcast 750 KO, VIN 11970 is fitted with the sandcast type tacho and speedo drives. I can only assume that anything pre this VIN was fitted with sandcast type drives also, but as we all know, nothing can be assumed with the early production bikes.
Anyone know anything on this subject
KP 

[736cc]

Every unrestored sandcast I've owned came w/ sandcast gauge drives. Probably in same territory as wrinkle tanks and rolled rims, some overlap. Sandcasts gotta have 'em, early diecasts might have 'em.

[bojje]

Hi! A couple of months ago I sent some pictures to Chris about the differenses.
First type of gear was sandcasted and above the cablenut it has a sharp edge. This kind is also different inside against the second and third edition. You are not able to use a first gear edition on the second or third one. The first edition seems to have been used up to VIN:s around 1500. If I´m wrong, don´t hesitate to tell us when they where changed.
Second edition looks as the first sandcasted one except above the cablenut, on this one the earlier sharp edge is rounded. This second edition I suppose were used from VIN around 1500 and up to more than 10000.
The third edition is the one we use to call the K0 gear. This gear seems diecasted or something like that and it has a 90 degree angle on each side of the gear. This kind is also used on the K1 speedo and tacho.
If someone has a perfect K0 speedo or tacho you just need to find a bad speedo or tacho of the second edition and change the gear. From what I´ve found out the gears on both speedo and tacho are the same so it doesn´t matter wich kind you´ll find.
If someone is interested in pictures just let me know and I´ll send them by mail.
Kind Regards to all of you sandcastmates, Bo from Sweden.

[Steve Swan]

Two (2)variants of sandcast drives i have seen and noted.

1.  Earlier drives have no bevel at area next to the threaded portion the cable attatches to.  This area of the early drive boxes is simply a right (90') angle, no bevel.

2.  Later drives have a bevel at area next to the threaded portion the cable attatches to, this bevel can be seen at      http://cb750sandcastonly.com/support21.htm#US  

[Steve Swan]

Early (without bevel) and late (with bevel) speedo drive box types.

[Steve Swan]

Here's a thread on the gauge gearbox topic from a few years back.