Topic: Nighthawk wheels on 75 CB750F

[DollarBill]

Has anyone tried to fit Nighthawk wheels to a CB750?  I am looking at 90's model wheels...  I know one issue for sure to tackle would be that my CB750F has a disk brake in the rear and these Nighthawks have a drum brake.  Anyone know the widths of the hubs and if they will fit???

[KB02]

Will they be a direct bolt on? No. But, the mantra of any bike customizer has always got to be: Anything can be made to fit.   

The two places you want to check, double check, measure, double measure, and triple measure are the offset distances from each side of your stock wheel and the axle bolt diameter. You want the NH wheel to be on the same center line as the stocker. Also, your axle bolt may be a different diameter. You will want to address that as well.

I am currently adapting the wheels off of a Katana to go on my K8. I've got my spacers built up and they fit great, but the katana axle bolt is a smaller dimension, so I either need some bushing like sleeves for the ends, or I'll need to fix the hub to accept the larger axle (which shouldn't be too hard, and may be what I end up doing).

[KingCustomCycles.com]

With enough time and money almost anything is possible.  1970's VW trikes come to mind with Honda front ends......

[Alan F.]

I've got a similar idea going on for my 750K3, which has a drum rear.  I'll be using the nighthawk front end, trees and 41mm forks, more modern brake (91-03) stem will use the 69-78 bearings (I'll use my tapered rollers) but is a little long, maybe I'll spin up a spacer or grind/ press/weld it, I'm unsure.  I chose a 17" front wheel from a 90 cbr1000, which fits with the nighthawk setup.  There were many bikes in the 90's that used many of the same fork and brake parts...cb,cbr, st, nt... to name a few.  I think my issue will be with the speedometer drive ratios, but I haven't looked into it yet, the rest is just measure, remeasure and measure again like KingCustom says, then make some new spacers to center things up.  I'm skeptical if the NH's 140 rear tire will fit my K3's swingarm, I've got some cleaning up to do before I can mock it all up...  Then there's the steering stops....  It's gonna be a good winter one way or another.  Have you given any thought to a CBR rear with the disk brake?  it might be easier and retain the 17' wheel size, unfortunately it's a 3-spoke wheel...  I'm planning NH rear(5-spoke), CBR front(3-spoke)

Keep my address on your short list, we can trade measurements and advice as we go, even though I'm working with a K-bike.

[DollarBill]

Thanks for the input guys.  I am sure it is possible given enough hard work and money.  I figured someone in here may have tried already with the NH wheels.  I have a guy that will sell me front and rear 99 NH wheels with brakes for $100 + shipping.  I think I am going to go for it....worse case scenario I can resell them on eBay.

I have looked at TONS of mag wheels for this project and I keep coming back to the NH.  KB08, you've seen this photo on my project yellow jacket thread...
Those wheels in gold...mmmmmmmmmmm


I'll keep ya posted Alan.  My bike is an F

[KB02]

Yeah... I think that will look cool....   

[Alan F.]

I'm thinking it'll look pretty cool too.

[DollarBill]

OH YEAH! 

[DollarBill]

I wish I had a 99 Nighthawk handy so I could do some measuring before I buy.  The only bike dealership/sales where I live is a Yamaha/Suzuki....I'd have to drive 50+ miles to San Antonio to find a Honda dealership.

[Alan F.]

What measurements do you need, these bikes were built the same from 91-03, and I have a 92.....   check your local craigslist, maybe there's a bike for sale closer to you...

[DollarBill]

Awesome Alan!  Understand, I have NEVER done anything like this before so I'm just guessing at what I need to measure. From what K802 says this sounds like the starting point:

The two places you want to check, double check, measure, double measure, and triple measure are the offset distances from each side of your stock wheel and the axle bolt diameter. You want the NH wheel to be on the same center line as the stocker. Also, your axle bolt may be a different diameter. You will want to address that as well.

By offset distances does that mean distance from edge of hub to each fork?  Same for swing arm?

These measurements would also be helpful.
- Distance between inner axle openings on the forks and swing arm.
- Diameter of both axels on each side.  I think I read that some axels are tappered so each end might be different???

Alan, would you be willing to take photos head on and from each side of the front wheel hub and forks with a few close ups?  Same for the rear?  I would appreciate it greatly.  If you can't its no big deal.

I checked craigslist and nothing but a couple of early 80s models and they are in San Antonio.  I'll keep checking though...

[eldar]

Part of the offset issue is the rear sprocket. Gotta be able to make it line up with the front. If you look, there is a wide spacer on the rear right side. Basically you want the wheel to center in the arm and have the correct offset for the sprocket to keep it in line with the front sprocket. That is my understanding.

I would love to go to mags. Better selection of tires probably AND the ability to go tubeless!

[Alan F.]

Not all mags are for tubless tires, the more vintage they are... the less likely they are for tubeless tires.  When I get my pics and measurements together, I'll be sure to include a pic of the bead ridge (for lack of a better name for it) inside the rim, it's a raised ridge around the rim on both sides that the tire's bead 'pops' on to when the mounted tire is initially inflated.  There's a better explanation to be had elsewhere.  But I'll try to get the pics and measurements tomorrow, unless my wife rides the nighthawk to work.....(it's actually hers...but most of the miles on it are mine)

As for other mags, Kawasaki around 1980 used an 18" rear with a drum brake and chain drive, I think it was on one of the 650-four models, and they used front rims that match it on dozens of models, some with single disk, some with dual disks.

[eldar]

Well most mags are tubeless but I suppose not all are. It is like spoked are not all tubbed but most are. But it would be nice to not have a tube.

[754]

Dollarbill, measure across both disc, outside to outside .. on both bikes and compare.. note thickness of discs and diameters.

you can do this with a tape measure and get an idea of how much difference there is.

[KB02]

For what it's worth, here is the measurements that I took for my wheel swap. The lines are kind of hard to see in the picture, but basically, I just started wit the wheels at center and then measured out each side so I knew the dimensions of where everything was located. From there you can determine if you need spacers (NH wheel narrower that stock) or if it will work at all (NH wheel set up too wide to fit in stock swing arm).



In the upper right corner, you can see that my sprocket is going to be offset by about 5mm. I have to work on that.

[Alan F.]

Modern Mags are tubeless, but the mags that were made as bolt-ons for our bikes are all tube type mags.  This is one of the reasons I chose the NH wheels, They just had the most going for them, besides If I find out that the NH parts won't fit my K3 I can use them for the NH....

I'll get pics as soon as possible, camera is in the car, car is being worked on today.......that's my story and I'm sticking to it.   
I'll get some measurements and post them as soon as I can today. 

I'm eliminating many if the variables in the front end by using the WHOLE front end, steering stem and steering stops as well as speedometer ratios are pretty much my only concerns there.

[DollarBill]

Alan, do you know yet how much modification, if any, will be required to get the NH font end on your K3?  I have been thinking about this as an option as well since I have a source for a parts bike.

[eldar]

If I remember correctly the f2/3 wheels are tubeless but then it was a crap shoot back then anyways. I would like tubeless so much that I have toyed with the idea of sealing my rims after my last experience trying to get my tire off to replace the tube! I can say it was NOT fun and a couple of times I have to stand on the sidewall to get the tire help things along! but then I think that would rather just have a more modern wheel anyways.

[Alan F.]

Alan, do you know yet how much modification, if any, will be required to get the NH font end on your K3?  I have been thinking about this as an option as well since I have a source for a parts bike.

The steering stem will use the same tapered roller kit that the 69-78's use, The stem is the same diameter where it counts, the difference is that the stem is longer.   So first I'll make up a spacer for the bottom of the stem and bolt it up, if I decide that I trust it, I'll make up some steering stops and be good to go.  The NH uses a mechanical speedo drive and I'm planning to use the NH's cable to my K3 speedo, but I don't know yet if that's going to work, ratios and tire size and all... might just go with a bicycle computer...

I haven't mocked it up yet, I've got quite a bit of cleaning up to make space for it, and not much time to spend at it....

[Alan F.]

OK, so here's a couple of diagrams showing the measurements that I took this morning, some are with a tape measure, some with a vernier caliper, all measurements are in inches.
Could someone provide these dimensions from an sohc cb750?  my bike is in too many pieces right now...

[Alan F.]

D'oh, the forks diagram has the 'Left side' label on the wrong side!

[Alan F.]

And a sohc cb750 rear axle is .885" diameter.....

[DollarBill]

Awesome Alan!  I'll try and get the SOHC measurements tonight for you.  So it looks like we are in the same boat as K802 and his rear Katana wheel.  Hopefully there is enough thickness to either allow for boring it out a little or coming up with some sleeves that will work to fill the gap.

K802, any progress on yours?

[eldar]

Well there are a number of bearing sizes. Might be possible to find bearings to prevent having to jerry-rig a sleeve.