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Author Topic: Swapping an K7 rear wheel for an F1 set-up  (Read 1333 times)

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Offline Wannabe Racer

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Swapping an K7 rear wheel for an F1 set-up
« on: August 10, 2015, 07:53:14 AM »
Hi everyone,
please forgive me if I'm asking questions that have already been asked in the archives... but my searches produce nada.
I have two CB750 Ks - Ones an import K8 that is a pile of rusting scrap but with low mileage and hasn't run for 17 years. The other is a UK K7, high mileage... but it's been messed around with (someone has added an F1 tank and seat unit, double disc front end and butchered it a bit with a lot of non-standard bits.

Now then, the plan is to 'Cafe' the rust heap K8 with bits from the K7/F1 hybrid and use the salvageable bits from the K8 to kind of restore the K7.
What I wanted to know was can I successfully fit an F1 wheel & Disc brake unit, reservoir etc on the K8 cafe project? I'm assuming the F1 has an 18" rear wheel so will have to use the shocks (or at least that shock length) but also assuming the swing arm for the F1 was the same length as the K7/8... is that a wrong assumption?

Can anyone give the low down on just what I need to consider, please?... Before I go and source a third donor bike.

Really appreciate you taking the time to laugh, Guffaw read my begging scribble... and even more grateful if you can help let have some good info!  :)
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Offline 70CB750

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Re: Swapping an K7 rear wheel for an F1 set-up
« Reply #1 on: August 10, 2015, 08:09:20 AM »
Not sure if it helps, but I put F2 wheels in K3 frame.

http://forums.sohc4.net/index.php?topic=115305.250

For the rear brake I got MC from 200? 900RR Honda and adapted the K pedal.
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Offline Don R

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Re: Swapping an K7 rear wheel for an F1 set-up
« Reply #2 on: August 10, 2015, 08:14:52 AM »
I'd plan to swap the swingarm too and know the master cylinder mount will need some fabrication. I have a wrecked F0 with a good backhalf that I plan to use someday too. I'll most likely weld the F mount but possibly with a more modern M/C. (just for parts availability)
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Offline Wannabe Racer

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Re: Swapping an K7 rear wheel for an F1 set-up
« Reply #3 on: August 10, 2015, 08:15:26 AM »
Thanks 70CB750.
I have to admit to not being a welder... a Sparky but not a welder. I don't mind taking an angle grinder to the frame and letting someone else do the welding... I'm just chicken!
Ill seek the easier route and see about direct swaps.

Thanks again.
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Offline Wannabe Racer

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Re: Swapping an K7 rear wheel for an F1 set-up
« Reply #4 on: August 10, 2015, 08:16:57 AM »
Thanks Don R.
I'll try and source the swing arm at the same time if I can't source the whole F1 donor bike.
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Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Swapping an K7 rear wheel for an F1 set-up
« Reply #5 on: August 10, 2015, 02:30:04 PM »
Use the K7/K8 rear sprocket carrier on the F wheel.
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Offline Retro Rocket

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Re: Swapping an K7 rear wheel for an F1 set-up
« Reply #6 on: August 10, 2015, 03:20:14 PM »
Quote from: Jerry Rxman Griffin aka MuthaF'er on August 10, 2015, 02:30:04 PM
Use the K7/K8 rear sprocket carrier on the F wheel.

+1, the K7/K8 engine has a 10mm wider output shaft so you'll need the sprocket carrier off the K7/K8 to match...
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Offline Short shins

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Re: Swapping an K7 rear wheel for an F1 set-up
« Reply #7 on: August 17, 2015, 01:04:36 AM »
Well the factory did it..
I guess it was a way of getting rid of some bits they had lying around..
My 1977 has a 17" rear K7/8 sprocket carrier, a F1 hub and disc(the F2 has Comstars) with F2 carrier and calliper/master cylinder, not sure about the swingarm. Also of note are the F2 style footrest hangers. according to the numbers the frame is F0/1





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Re: Swapping an K7 rear wheel for an F1 set-up
« Reply #8 on: August 17, 2015, 02:52:58 AM »
Congratulations: you just built yourself a Japanese specs CB 750 K7. If you ever want to go back to the 4in4, I have the original bracket to accommodate the brake line for that model. :)
Anyway, nice upgrade.

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