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Author Topic: CB750 frame swap.  (Read 1393 times)

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Offline Sam Green Racing

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CB750 frame swap.
« on: May 18, 2020, 04:42:19 PM »
Instead of using the Gordon type top tube frame conversion kit to make working on the top end more easy, has anyone used the Automatic frame to achieve the same result ?

Sam.
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Offline Medyo Bastos

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Re: CB750 frame swap.
« Reply #1 on: May 18, 2020, 06:02:49 PM »
Yes Sammy


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Offline Sam Green Racing

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Re: CB750 frame swap.
« Reply #2 on: May 18, 2020, 06:10:04 PM »
Quote from: Medyo Bastos on May 18, 2020, 06:02:49 PM
Yes Sammy


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What engine did you use ?
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C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline Medyo Bastos

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Re: CB750 frame swap.
« Reply #3 on: May 18, 2020, 06:10:32 PM »
K8


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Offline Sam Green Racing

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Re: CB750 frame swap.
« Reply #4 on: May 18, 2020, 06:26:15 PM »
hahaha, not what I wanted to hear, my guess is that the K8 and F2 go straight in.
I'm trying to find the ones that have had problems, I'm sure the lower Ks don't work but not sure where the cut off is.

Bed time in the UK a few hours ago, night mate.

Sam.
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C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Online Don R

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Re: CB750 frame swap.
« Reply #5 on: May 18, 2020, 07:11:47 PM »
 I was working on a project I was going to call called  F'n A, man. It got sidelined by a K0 find.  Shoved against the wall at the moment, the A rims are on the f hubs at least. I was going triple disc, mostly driven by having a wrecked F a no title A and wanting a cool drag bike.
 The drawback is the F or K or 400F tank doesn't fit the A frame without mods.
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Offline 754

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Re: CB750 frame swap.
« Reply #6 on: May 18, 2020, 07:15:51 PM »
All the motors should fit. Tank is a big problem  only the A tank fits,  the rest you have to cut,
« Last Edit: May 18, 2020, 11:16:28 PM by 754 »
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Offline Old Scrambler

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Re: CB750 frame swap.
« Reply #7 on: May 18, 2020, 07:19:56 PM »
Frank is correct.......I have a K4 in an A-frame for my CBR Bonneville bike.......with an F2 head.
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Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
'67 Triumph T100C
'73 750K3 Owned since New
'77 750F2 Cafe Project
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Offline scottly

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Re: CB750 frame swap.
« Reply #8 on: May 18, 2020, 07:26:47 PM »
The difference in the clutch motors regarding frame swaps is in the offset of the counter-shaft sprocket: The K7/K8 F2/F3 position the sprocket about 10mm farther outboard than all earlier bikes. It's easy to swap an early motor into the late frame using an off-set front sprocket, or possibly fitting an early rear sprocket carrier?
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Offline Sam Green Racing

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Re: CB750 frame swap.
« Reply #9 on: May 19, 2020, 06:41:18 AM »
Quote from: scottly on May 18, 2020, 07:26:47 PM
The difference in the clutch motors regarding frame swaps is in the offset of the counter-shaft sprocket: The K7/K8 F2/F3 position the sprocket about 10mm farther outboard than all earlier bikes. It's easy to swap an early motor into the late frame using an off-set front sprocket, or possibly fitting an early rear sprocket carrier?

Thank's Scottly, that was everything I wanted to hear but have you any Idea why the front sprocket is placed so far out ?
Is it possibly because the Auto, K7 K8 and the F2 F3 have a wider final drive output shaft Bearing ? Also, I think I measured it at being 5/8th of an inch.
Dennis, how did you overcome this on your Bonneville Bike, did you use an offset front sprocket or some other idea ?

Sam. ;)
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C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike

Offline Medyo Bastos

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Re: CB750 frame swap.
« Reply #10 on: May 19, 2020, 07:36:16 AM »
Sammy I’m not following you. Just match the motor countershaft sprocket and rear wheel cush drive. The early and late frames including a frames will fit.


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Offline Old Scrambler

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Re: CB750 frame swap.
« Reply #11 on: May 19, 2020, 08:35:50 AM »
Sam.......easy way is to use an early K swingarm and wheel. Just remember to shorten the upper-left shock stud. On my CBR I used a custom swingarm taken from a Kawasaki dirt-bike. The goal was to keep the rear of the bike as narrow as possible to get my big feet tucked-in ;)
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Dennis in Wisconsin
'64 Triumph Cub & '74 Honda CB750 Bonneville Salt Flats AMA Record Holder (6)
CB750 Classic Bonneville Racer thread - http://forums.sohc4.net/index.php/topic,135473.0.html
'63 CL72 Project(s)
'66 CL77 Red
'67 Triumph T100C
'73 750K3 Owned since New
'77 750F2 Cafe Project
2020 ROYAL ENFIELD Himalayan

Offline Sam Green Racing

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Re: CB750 frame swap.
« Reply #12 on: May 19, 2020, 10:34:22 AM »
Quote from: Medyo Bastos on May 19, 2020, 07:36:16 AM
Sammy I’m not following you. Just match the motor countershaft sprocket and rear wheel cush drive. The early and late frames including a frames will fit.


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It's OK now Medyo, I've found out what I needed to know thanks to scottly and Dennis.

I wasn't sure when the gearbox sprocket was moved further out in the K series but now I know.

I'm not building another bike, it's just that people keep asking can I do this, can I do that.

Sam. ;)
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C95 sprint bike.
CB95 hybrid race bike
CB95 race bike
CB92
RS 175. sprint/land speed bike
JMR Racing CB750A street ET drag bike
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