Author Topic: How do I make this work...?  (Read 913 times)

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Offline Holshot

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How do I make this work...?
« on: October 13, 2016, 06:09:30 PM »
Hey guys,

First off, let me say in the brief time I've been a member on this forum I've learned so much by reading and asking questions which have always been answered with great detail. That said, I'm planning on doing a cafe build, not with my clean original '74 but rather a basket case '71, over the winter to stave off the depression from not being able to ride. I'm fairly new to the older bikes as I've only ever owned modern sport bikes, i.e. Yamaha R-1 and a Ducati Monster so the extent of wrenching was basic maintenance stuff, slip on exhaust and cosmetics, ect...

Now I am mechanically inclined and have restored many Fiat Spiders and owned/built many high horsepower '90s era Jap cars like Supras', 3000GTs', RX7s', EVOs', ect... so now that I'm dipping my toes into old Japanese bikes I'm doing my best to learn as much as I can and also hoping to rely on the old timers and pros on this forum to help me along my journey. Now that's out of the way... I used to dream of building a late 60s/70s hardtail Triumph Bonneville but then I fell in love with the Honda CB750 and that's all she wrote.

One thing I did love on the older British bikes like Triumph, BSA or Norton was the look of conical front drum brake with the huge scoop, pictured below... I thought to myself that this might look cool on my cafe build. I know, I know, I know that the braking power of disc brakes are far superior to a drum setup but this bike is being built for show as well as go and I can live with the slight decrease in efficiency. I want to clean up the bars and eliminate the brake reservoir so this is one way to do that. I did a google search and I haven't come across any CB750 with this style rim on it and I pulled the gun early on a eBay auction as they don't seem to come up that often with the hopes it will fit/work.

Well I just got her in the mail today and they both measure out to 19" and both have 40 spokes. Where they differ are the axle on the Triumph measures around 5/8 and the stock Honda rim was roughly 3/4. Next thing I noticed was the Triumph rim was much thinner and the Honda was wider. Measurements could not be taken just yet as both rims have tires on them and I couldn't find my calipers to get an exact measurement. The rim width isn't a huge deal as the rim I purchased is heavily pitted and the chrome is peeling so I'm ASSUMING I can just order a new wider rim, correct? I'm assuming if I ordered a 40 spoke, 19" rim that would solve that problem. What size rim is still is still up in the air and will take recommendations...

If my assumption is correct let me know... if not let me know ;-) my next problem is the axle. What/how do I address the smaller axle found on the Triumph rim to get it to fit in the stock forks on the Honda. Is it possible to get a bigger axle in that hub? Do I need to have a bushing/insert machined to go over the smaller axle and take up the slack? Again, I'm new to this stuff and hope that there is someone out there willing help and teach me the ways, haha... any ideas would be greatly appreciated!
1974 CB750K

Offline 754

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Re: How do I make this work...?
« Reply #1 on: October 13, 2016, 06:41:01 PM »
I would check the bearing OD,s first to see if you can get a bearing to fit, if going bigger, will have to bore out the centre sleeve.
 If you want to make the axle OD bigger, you could use sleeves or a bushing.
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73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline strynboen

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Re: How do I make this work...?
« Reply #2 on: October 14, 2016, 07:12:06 AM »
you can get bearings vho kombines inch and milimeters..so almost no mackining/bushings is needet..like 38mm autside and 1/4 inside diameter(only eksampel)
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Offline FunJimmy

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Re: How do I make this work...?
« Reply #3 on: October 14, 2016, 07:24:46 AM »
Very cool hub. I've always liked the look of a leading shoe drum brake.
Like strynboen and Frank have already said. Pop the bearings out and hightail to your industrial bearing supplier. They should be able to get you a few options. Even if you can't get the exact ID required to fit the 750 axle get the largest ID bearing that fits the hub. You may need to machine a new axle and larger is better.

Consider sending the hub to Buchanan's. They can set you up with a beautiful aluminum rim and SS spokes. Their wheels are amazing.
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Offline scottly

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Re: How do I make this work...?
« Reply #4 on: October 14, 2016, 08:46:46 AM »
The 750 axle isn't 3/4" where it goes through the bearings, it's 15mm, or .590".
Don't fix it if it ain't broke!
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Offline 754

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Re: How do I make this work...?
« Reply #5 on: October 14, 2016, 12:37:26 PM »
And if you can find a bearing that could work ,but is a mm or two smaller on the od, we machine sleeves to press in to make them fit.
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 seanbarney41

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Re: How do I make this work...?
« Reply #6 on: October 14, 2016, 07:11:20 PM »
Why dont you buy a cb450 front drum and bolt it on?...better yet, get the whole front end and you wont have to mess with the backing plate stay bar...plus I think it is known to be a bettet brake.
If it works good, it looks good...