Topic: The unexpected... CB750K spoke wheel TO COMSTAR swap. Help?

[CB750Noobie]

Hi guys,
This is my first post here-- I'm no stranger to working on motorcycles and have previously done an extensive custom rear wheel swap on a Triumph *BUT* I am completely new to Honda bikes. I recently began tearing down a 81 CB750K (DOHC - sorry for posting in SOHC forum, not many other active Honda forums) and I really want to get rid of these rusted Chrome Spoke Wheels rather than sandblasting them and powder coating them or the likes... already running spoked wheels on the Triumph, I want something entirely different.

I've done some digging online and every single article I have found is people bashing the Comstars, and/or people wanting to switch to the spoke wheels... I can't seem to find useful information addressing which specific wheels are the same size/width/bolt pattern, have a matching sized rotor/caliper mount fits, etc. Seems everyone keeps their research to themselves (or my search isn't netting the proper results).

Can anyone point my efforts in the right direction for which Comstars are used in the below builds(Which year/model of Honda the Comstars are from), and if those specific Comstars have compatible parts with their spacers, bearings, cush drive (rear), rotor size/caliper mounts, etc. for my 81 CB750K? I'm not afraid to fabricate something, but I'd prefer a direct swap. So do the 81 CB750C wheels swap directly onto my 81 CB750K-- for example My 81 CB750K has the single caliper up front (left), drum brake in the rear. Is this an issue when buying the wheel or can that rotor just be removed?... Questions like this that I have no experience with are what I'm seeking answers to before proceeding forward.

Personally, I really like the look of some of the Comstar wheels... to me it looks like classic Japanese muscle.
examples:
https://www.pipeburn.com/wp-content/uploads/2018/10/Hookie_Black_Swan_Hondas_CB750_Cafe_Racer_BIGS_01.jpg
https://i.ytimg.com/vi/dgxSlTRadis/sddefault.jpg
https://kickstart.bikeexif.com/wp-content/uploads/2018/05/honda-cafe-racer-caffeine-custom-1-625x417.jpg

I'm looking for actual guidance here... what years of Comstars (and from which bikes) will be a direct swap (and same wheel size) if there is one.

Cheers and thank you for your time, information, and thoughts.

[BenelliSEI]

See Piezl’s post, afew below this (“stumped on rear brake issue”. I think he’s doing this swap.

[CB750Noobie]

Appreciate the heads up, checked it out... I'm not even sure that his 78 CB750K is the same as my 81 CB750K. Thats an example of how  new to Hondas I am. But I see a lot of parts that specify they fit UP to a 78 or 79 CB750, but it rarely includes the 81

[scottly]

The only sohc 750s that had Comstars were the '77/78 F models. They had a five bolt brake rotor mounting, and were not rated for tubeless tires. Your best bet may be from an '81 or maybe '82 dohc 750 F?

[scunny]

650Z models are comstar with double disc. Tubeless as well.

[CB750Noobie]

Scottly, appreciate the thoughts... those appear to have the dual front disks for the model with the two front calipers. Does you know if there are mounting issues with that if I remove the right side rotor? Again mine only has the left side caliper/rotor.

[scottly]

Yes, you should be able to remove the right side rotor, but you may need shorter bolts. Most people want to upgrade to dual brakes...
The caliper mounting bracket for the spoke wheel may or may not align with the left side rotor on the Comstar; you will have to verify that yourself. 

[CB750Noobie]

Scottly, thank you again for the input. However that's what I'm trying to figure out before ordering a new wheels... I just wish someone who's attempted/completed this swap would provide input-- I found a few other threads, but all 78 and earlier CB's  Shipping isn't cheap and the last thing I want is a headache between ordering a bunch of wheels that wont work and then having to resell them, or getting the front fitted fine and finding out on the back end that the rear wont work for whatever unforeseeable reason.

[CB750Noobie]

Postes by SeanBarney41 and BankerDanny are what I've seen most information in... bump

[Bankerdanny]

Reverse Comstars (black with the silver edges) were standard on the '81 750C , so it seems reasonable to think they should bolt up to a 750K from the same year.

I think that regular Comstars were used on 81 K's in other markets, and I know they were used on the last couple years of the SOHC4 750 Hondamatic too (750A) so might make for an easier swap.

[CB750Noobie]

Reverse Comstars (black with the silver edges) were standard on the '81 750C , so it seems reasonable to think they should bolt up to a 750K from the same year.

I think that regular Comstars were used on 81 K's in other markets, and I know they were used on the last couple years of the SOHC4 750 Hondamatic too (750A) so might make for an easier swap.

Appreciate the reply Bankerdanny, so my (81 CB750K DOHC's) front rim is a 19 x 1.85, and the 750C (or comstars from the K) are a 19 x 2.15, I'm wondering if the mounting point of the wheel (center) is any different. I mean it's $80 for a wheel to try it out, so if no one has additional insight (hard to believe no one else has successfully posted this anywhere) then this may be the route I pursue.

If you have any additional thoughts let me know.

[MauiK3]

Or just get alloy rims and stainless spokes, no more corrosion.

[Bankerdanny]

Reverse Comstars (black with the silver edges) were standard on the '81 750C , so it seems reasonable to think they should bolt up to a 750K from the same year.

I think that regular Comstars were used on 81 K's in other markets, and I know they were used on the last couple years of the SOHC4 750 Hondamatic too (750A) so might make for an easier swap.

Appreciate the reply Bankerdanny, so my (81 CB750K DOHC's) front rim is a 19 x 1.85, and the 750C (or comstars from the K) are a 19 x 2.15, I'm wondering if the mounting point of the wheel (center) is any different. I mean it's $80 for a wheel to try it out, so if no one has additional insight (hard to believe no one else has successfully posted this anywhere) then this may be the route I pursue.

If you have any additional thoughts let me know.

The wider rims don't matter. It is only the width of the center section that matters, and it can generally be addressed by larger or smaller spacers.

[kerryb]

Early on...I bought a 77 550k that had comstars put on it.  I found that a 78 cb750 spoked wheel was a direct swap to the rear end with one spacer change. For the front I swapped on a whole 78 750 front end.   Currently I'm working on an 82 cb650sc with comstars on it. Dual disc front, drum rear.  I could take some measurements from them if it will help.

[CB750Noobie]

Bankerdanny, yep especially because the 81 apparently have a wider fork setup than the earlier cb750s (78 and earlier) so the wider rim isn't an issue. Fabbing a new spacer is no issue if thats the worst thing I run into for the front.

Kerryb that would be great... I'd be curious though how different the 650s ID (for the front axel) is and how wide the actual inner section of the wheel is, and if it's any different than my 81 CB750K. For now I am trying to avoid the front end swap/dual brake conversion-- the bike only has 5.8k miles on it, and the front end is generally in excellent condition for its age. So if there is a way to wheel swap while keeping my brakes I'm fine with that!

Everyone, I appreciate your insight and support on this. Seriously its awesome. As I get into this thing, and order wheels I will be sure to post photos of progress and such. (Again, still open to feedback if someone has done this and chimes in)

[Bankerdanny]

One thing to pay attention to is the front brake rotor. The wires on the older SOHC4's used a 6 bolt 2 piece rotor without much dish to the center. The Comstars on the later F models used a 5 bolt rotor that was smaller than the single front from wire wheel 750's and were a one piece design with a deeper dish. The spacing on the rotor was different because the front calipers were mounted behind and directly to the lower fork legs.

When I put F3 forks and brake calipers on my wire wheel F1 to get a twin disk front I had to use smaller rotors from a CB550 and make spacers so that the brake pads were correctly centered.

You will be able to do what you are trying to do, but it might not be a simple weekend project.

[seanbarney41]

Postes by SeanBarney41 and BankerDanny are what I've seen most information in... bump

I like comstars better than a crappy old steel rimmed spoke wheel because they are round and true, sturdy, no heavier than what they replaced, and I have never seen one to have rust problems.  Nothing worse than endlessly polishing spokes to no avail...That said the only bike I have ever worked on that had 'em is my 1978 sohc cb750f3.  And I have never messed with any of the dohc's.  I have been told that the "boomerang" comstars are a direct swap onto the f2/3's and I am pretty into that, but have never got my hands on the parts.  I have generally found that Honda built a lot of interchangeability into the wheels and brakes so I would imagine that this intended swap is possible.  When searching for parts sources, don't forget about the 80's Honda twins...lots of those use comstars too, and are likely to have a single front disc brake.