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Author Topic: 78 cb750 wheel diameter change  (Read 882 times)

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Offline bianco013

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78 cb750 wheel diameter change
« on: March 15, 2019, 10:21:38 AM »
Hi all. I am Working on bringing a 78 cb750 back to life. Everything is going well but I want to talk wheels. The bike came with a 2000-2001 gsxr fork/brake/ handlebar setup on it and I want to keep it that way. The PO didn’t build the bike but he mentioned to me that the rear wheel/rim was used on the front and laced with a hub that worked. The current setup image below is a 120/90/17. The rear is a 150/70/17. I wouod Like to keep the rear but I want to change the front to a 18 inch wheel for tire options as well as availablify it will be a 110/90/18. What is the best way to go about this change of the rim/spikes? Any thoughts/insight will be appreciated.
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Offline bianco013

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Re: 78 cb750 wheel diameter change
« Reply #1 on: March 15, 2019, 10:23:11 AM »
See front wheel below
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Offline Bankerdanny

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Re: 78 cb750 wheel diameter change
« Reply #2 on: March 15, 2019, 11:01:34 AM »
Best or cheapest?

Best would be to send the wheel to Buchanan's and have them lace up the 18" rim of your choice. They custom make their own spokes, so they will sort the correct size to work with your rim.

The seller probably used the front conversion hub made by Cognito Moto, whose owner Devin is a member here. I would ask the seller what front hub he used. If it was Cognito then you can contact them to find out what spoke length you need for an 18" rim. They also assemble wheels, so you could send the hub to them and have them lace up a rim.
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"The problem with quotes on the Internet is that you never know if they're true" - Abraham Lincoln

Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline bianco013

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Re: 78 cb750 wheel diameter change
« Reply #3 on: March 17, 2019, 06:55:49 AM »
I ended up taking the rotor off and this is NOT a Cognito hub, it seems that the builder used some sort of "adapter", if you could call it that, to connect a hub (possibly a CB750 front hub?) with the rotor shown. Not sure if I am comfortable with this setup. I think my best bet is to, gasp!, suck it up and buy a Hub/wheel combo and know its the safest bet. I'll attach a picture when I get one. Is Cognito moto the only place for them? I can't say it is exactly within my price range... any other options would be great!
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Offline Bankerdanny

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Re: 78 cb750 wheel diameter change
« Reply #4 on: March 17, 2019, 07:04:45 AM »
Interesting. I hadn't enlarged the photo. That does look like a stock hub. How did he adapt it?
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"The problem with quotes on the Internet is that you never know if they're true" - Abraham Lincoln

Current: '76 CB750F. Previous:  '75 CB550F, 2007 Yamaha Vino 125 Scooter, '75 Harley FXE Superglide, '77 GL1000, '77 CB550k, '68 Suzuki K10 80, '68 Yamaha YR2, '69 BMW R69S, '71 Honda SL175, '02 Royal Enfield Bullet 500, '89 Yamaha FJ1200

Offline 754

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Re: 78 cb750 wheel diameter change
« Reply #5 on: March 17, 2019, 07:23:37 AM »
 Show us the other side of wheel. Or the parts you now have off.
 Nothing wrong with a spacer or adaptor if it's built right.... now if it does not center onto the hub it may be a problem.
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Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline bianco013

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Re: 78 cb750 wheel diameter change
« Reply #6 on: March 17, 2019, 08:59:32 AM »
Shown are both sides of the wheel. I dont Think I’m comfortable with that. It’s one solid piece, and I’d that a cb750 speedo sensor? The reason I’m not just using this wheel again is because it’s bent/cracked fork an accident. Thanks for the help everybody
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Offline 754

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Re: 78 cb750 wheel diameter change
« Reply #7 on: March 17, 2019, 09:38:56 AM »
Ok so you have a 77 or 78 K front hub.
 A disc adaptor.. is it steel ?
 Adaptors on axle to fit larger fork holes
 Stock Speedo drive, that looks, like it was not used to drive the cable.

So it looks like it worked but the spacer adaptor is a bit crude, not a lot of meat around the disc mount holes. And it looks like it  does not fit nicely to the hub, which would centre it and keep things running true.
 I have made many adaptors similar to that , and they work well , but the fit should be better..

What is wrong on wheel ? Rim bent L
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Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline bianco013

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Re: 78 cb750 wheel diameter change
« Reply #8 on: March 17, 2019, 09:46:37 AM »
See the bend below. It went into a guard rail post at about 20mph. The reason for all of this because  of that bend. The tire on there is really my only option at that size and i cant Really go any smaller because of how close to the ground it is. The exhaust scraped before. I figure If I go to an 18 there  are more tire options. Specifically, the roadtec 01 that I want to run. Comes in a 110/90r18 that is very close to the overall diameter of the wheel/tire you see here.
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Offline 754

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Re: 78 cb750 wheel diameter change
« Reply #9 on: March 17, 2019, 10:46:50 AM »
That , get it straightened .
 How much runout at the bead Inside?
Take a black marker to the scrape right now  looks better already doesn't it ?
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Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline bianco013

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Re: 78 cb750 wheel diameter change
« Reply #10 on: March 17, 2019, 05:55:24 PM »
Yeah, I am hoping to get the tire off this week to see the situation inside. What tires do most of you guys run if you have a 17in up front? Maybe I can just stick with this one.
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Offline 754

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Re: 78 cb750 wheel diameter change
« Reply #11 on: March 17, 2019, 06:46:27 PM »
 The higher  the second number the taller the tire..
 Did you use a Sharpie to make the rim look better ?
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Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline bianco013

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Re: 78 cb750 wheel diameter change
« Reply #12 on: March 17, 2019, 07:53:29 PM »
Ha - Ha. Yes sharpie made it look shiny new  8) Im going to have the rim gone over by the tire shop but it looks like its gonna be a go! thanks for the help
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