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Anybody looking for just that correct set of Comstar rims should check out the CB750C.com forum but more to the point the CB1100F.net 'F-orum, where I'm always blathering on about wheels and Comstars and wire-spoke rims. There's a member an 'F-er I should say, "MELCHIRO" (among others) - who rebuilds Comstars from several different wheel parts, so as to change the size of rim or type of hub - there's a LOT you can do with these wheels. Myself I'd be very curious about swapping to a smaller diameter drum back there, so as to lighten the rear wheel considerably. I'd also be keen to try setting up a 'K or 'C model with an 18" rear BOOMERANG Comstar wheel. From the CB900F2, 3.00x18" rim, but on a smaller drum from the XBR500 for instance. However there are ALSO some 17" rims of the Boomerang type, with a 3.50x17" rear rim - might just be feasible to swap out a hub in THAT rim, I'm uncertain which drums would be suitable for that size of Boomerang - it's not necessarily another 17" Boomerang, just a drum with the correct diameter of the six lugs for bolting up the Boomerang spoke plates. There's gotta be SOMETHING I dunno what it would be. Most of the bigger bikes with Boomerangs they all had disc brakes. Whereas there were other Boomerangs in 18" with drums, but those drums were considerably smaller. However there's gotta be SOMETHING. Something related to the XBR - perhaps the rear drum from the MXV250F or MVX250F - how do you spell it? THAT thing had a more intermediary sized drum, which was probably more on par with the hub from the CBX750F Bol D'Or and VF1000F Bol D'Or where the 3.50x17" Boomerang rims came from.
Now - as for a dual-disc front end, when you want spokes you wanna go with the GL1000 front hub. Don't worry too much about speedometers, as you wanna run with a magnetic rotor bolt and electronic speedo pick-up, possibly even using the sheath of the old speedo cable and a hollowed out speedo housing, so as to disguise the thing as "old's-cool" original parts.
But yeah what you want for a FORK is ideally the 39mm CB900F version, GL1000 GL1100 even - and 37mm forks as a less preferred option. You wanna use the non-TRAC caliper hangers from GL1100A Aspencade or the CBX pro-link (monoshock) models, with the twin-pot calipers from later year - THIS way you can utilize the larger 296mm rotors. And whether you go with the double-thick rotors from the likes of CB1100R '82-'83 models, CBX pro-link, GL1100 & GL1200 Aspencade models - with the vented center vanes directing cooling air down through the center of the rotor ... OR you could use the rotors from the REAR brake of CB750F1 1975-1978 SOHC Super-Sport models AND GL1000 rear discs so as to save some weight, and these are the rotors to be cross-drilled for even further weight savings - What you WANNA do is swap out the central carriers, drill out the rivets on the nine-rivet type rotors, replace 'em with stainless rivets sold for affixing new sprockets to the Harley "Juice-Drum" rear brake.
This stuff looks more or less OEM stock for the later model SOHC CB750K however you're now working with rotors of the 300mm-ish class. A decent up-grade in braking without too much change in the original good looks. I suppose the same thing could be done with the original '69+ swinging-caliper-bracket type forks, you'd just need to create a different caliper swinger to off-set those few extra mm's needed to make it fit. But who the heck wants the 35mm fork tubes anyhow? Maybe on a CB350F or CB400F with their original fork starting out at 33mm, maybe THOSE bikes could use it. But a DOHC 750 you should at the very least be looking at the 37mm fork upgrade, far better the 39mm - and anything bigger like a Wiseco Big-Bore kit for 750, should be looking at the 41mm TRAC forks from GL1500 & VF series bikes, or even simpler the 43mm forks from the '90s era CBR models - but with the steering stem from the CB900F alloy yokes (including 37mm versions off the '79 vintage CB900FZ model) pressed into the CBR lower yoke.
However if you're HAPPY with the smaller 276mm rotors, the later DOHC forks will work straight across with the GL1000 front hub and SOHC type rotors. You COULD modify the single-disc CB750K DOHC wire-spoke front hub to take a spacer and dual discs, I suppose. That is, IF the five-bolt carriers mean that much to you.
Also, it should be noted that the sprocket carriers of the CB750C & CB750K DOHC are pretty much the same as the CB750K8 which has the chain-line offset the further 10mm to the left. However there are ALSO some off-set sprockets from the likes of "Cycle Exchange" which bump things further out, as does the drive sprocket from the pro-link ('81-'82) CBX, so that a person could figure out a very wide off-set chain for a very fat rear tire. At least, on the wire-spoke stuff. There's gotta be some off-set sprocket carriers I believe the CBX pro-link version for the five-spoke type Comstar hubs and similar versions of Boomerang Comstars like CB900F2 etc which utilized the same hub center/core or bolt-patterns etc, as the regular Silver Comstars & Black/Reverse Comstar wheels. Later CBX750F/VF1000F type Comstars use a different brake rotor, sprocket-carrier etc - than the earlier type. However with all axle spacers and parts from the original bike, they supposedly bolt straight up! Pretty cool, huh? Anyway yeah, I BELIEVE there are some five-bolt type off-set Sprockets for wider clearances ON those same later-era Boomerang type Comstars.
Of course for the simplest swap over to a 17" rim, one could rebuild using the CB750C rear drum into the GL1000 & GL1100 rear wheel, which is 2.50x17".
I've scored some cheap ($39.99ea on eBay if you can believe it - not sure if there are any left?) 40-hole Supermoto type rims, in 4.25x17" & 5.00x17" sizes, but they're drilled for the smaller Harley rear hubs, which are closer to the Honda FRONT hub in diameter & consequent drilling patterns. However IF they can be re-drilled for some fatter spokes (to open up the holes and make the old alignment disappear entirely) and made to FIT say, the CB750K drum or CB750F1 disc hub, the GL1000 shaft-drive rear hub - they've all got the same spoke lacing 'cause the hubs are the same diameter - but yeah what a cool bike THAT would make! I've also scored some rear rims from Harley AMF era XLH Sportsters etc - drilling pattern is similar to Honda front wheels, and they're basically an un-stamped/un-marked BORRANI 2.50x18" shouldered/flanged drop-center alloy rim - PERFECT size for these bikes, same size as the CB750K DOHC wire-spoke wheels but ALSO the same as the front Boomerang Comstar wheel from CB1100F, CB1100R, CBX750F Bol D'Or models, CB900F2, etc. Scored THEM for $40ea from eBay too - with a re-drilling and new stainless spokes, this could still wind up as one affordable alloy rim wheel rebuild. And in simply awesome sizes too.
Incidentally I got Buchanan's to re-drill a rim for me, and the price was VERY reasonable - invoice said $20, though I suppose this might vary based on how radical of a job they've gotta do. But yeah they've built my front wheel for the "KZ440LOL" so far, which is the Suzuki GT750J "Water Buffalo" 4LS drum hub, squeezed into a 3.00x16" Borrani alloy rim. For Maxi-Scooter tires.
Just saying - it's very hopeful they'll be able to re-drill these 17" fat rims for me as well! Sure would make for some awesome rims on an Old-'Wing Goldwing. I guess the conversion to wire-spokes on the later models is quite difficult.
However the best method I've seen YET for wire-spoke conversion on a shaft-drive bike, was a guy on the CB750C.com forum, 6pkrunner - he took his CB900C shaft-drive rear hub, spun it down on a lathe so that only a PLUG remained of it - and welded it inside of a lathed-out DRUM hub. Strikes me that this could even work on much smaller drums, so as to save some weight! But yeah HIS bike looked like a factory original CB900C wire-spoke model. GORGEOUS job he did on it. With the external cooling fins of the CB750K rear drum, I dare say that wheel looked BETTER than the CB750K1 & GL1000 rear wheels, with the huge GAP between the spoke flanges.
I'd love to see somebody set up a SERVICE doing that to wheels, kinda like how Kosman Industries used to (?) weld up RIMS to create wider wheels. And the hub thing should be a lot cheaper, being that it's much the same process but scaled down to a smaller lathe, smaller welding jigs, less running inches of weld bead, etc. Of course you'd still have the SPOKES and the wire-spoke RIMS to deal with. But if they were all done to a similar standard size, the same economy of scale which benefits HARLEY AFTERMARKET rims & wheels etc, would bring the prices down when the hubs are all the same thing the spokes are all the same thing, and only the sizes of rims are different. Even the off-set or "DISH" of a wheel would be set up at the point where the hubs are welded together. Eventually it would be possible to stick wire spokes on EVERY type of bike. Soup to Nuts!
Happily, swapping wheels on the CB750C & CB750K DOHC have got to be about the simplest of wheel swap projects one can take on. I WISH to hell that I'd stuck a rear drum brake onto my 900 over here! Rear DISC brake swaps are a little more complicated. To say the least. And when it comes to a rear disc hub with a cush-drive and a 20mm axle? Look AROUND - there are but a handful to choose from, and they're all heavy as shit. CB750F1 SOHC, GS1000, KZ1000LTD, KZ1000A/KZ750B - you could include the KZ1000CSR hub if you don't mind the 48-spokes or the fact it weighs even more than it's competitors - heavy as they already are. It's got some nice options for a disc though, from some of the later Kawasaki 1500cc V-twins. Nice cross-drilled little rotors which look the part of a vintage Superbike rear brake. But that means a custom rim and a heck of a lot of spokes.
I've got a "SPARE" 4.25x18" Akront rim, two of 'em that means - one for the CB750F1 SOHC rear hub, and the other one drilled for a Harley pattern. So I've been thinking of using the "Front Hub Trick" where you use a front hub with a bolt-up cush-drive and front rotor spaced for the rear caliper - which means one needs a special caliper hanger. 'Cause the front rotors are 276mm whereas the rear rotors were 296mm - then again one could swap out the carrier etc, use a 296mm rear rotor on the front carrier, OR build a spacer so as to bolt the rear rotor to the front hub. THEN one could se the standard caliper & caliper hanger. Either way, there's some custom work involved.
Personally, I plan to use a cush-drive cut off from a smaller Honda hub rather than a later era Ducati cush, so that the whole thing is "period-correct" - as well as a small front rotor wherever possible.
On the KZ750B/KZ1000A hub I've got handy, the front Comstar rotors fit and one bolt lines up - meaning drill three more holes, possibly block up the others, and you're in business. There are ALSO the smaller composite rotors from the likes of CB350F/CB400F I think that might just work - in a perfect world. Same deal with the CB750F1 SOHC rear hub, the rear rotors from early DOHC bikes the single-piece light-weight rotors, THEY fit the hub but again a five-hole rotor on a six-hole hub. But one hole lines up perfect and the center "boss" hole fits perfectly. So at least that one's a light-weight rotor which fits to the OEM caliper hanger no problem. I'd much rather find a way to fit a smaller CBR rotor on the scale of 220mm-260mm, but I want to go all period-correct with this stuff. Maybe it's possible these CB350F/CB400F rotors would fit, 'cause while the carrier's center has four bolts, the rivets holding the circumference in place had only six rivets - unlike the bigger ones which had nine rivets. I don't expect the rivet holes would line up perfectly, however if the thing's gotta be milled out to fit, the six rivets could lie just outboard of the six new bolt-holes. THEN I'd need to dig around for a proper caliper which would work. For a period-correct job, I'd expect a CB350F/CB400F front caliper could work on a flat plate of billet/plate etc. OR a cut-down carrier for one of the earlier rear disc brakes. Ideally keeping the same look as the CB900F version with all the holes drilled through it. Dunno whether that could be accomplished - surely it's possible if you WELD the damn thing together. But I'm picturing it just cut down and bolted together. The FLOATING nature of those calipers is what makes it difficult. Simple enough to mill a hole for BOLTS, but the sliding pin with the rubber seals etc, now THAT would be a tricky wicket. Probably gonna have to be cut down for a new axle hole, and starting out with one of the earlier SOHC caliper hangers. I guess THAT could work - add on some spacers to either side of that thinner center portion of the hanger.
See how much simpler it is when you use those 296mm caliper hangers up FRONT? If you wanna adapt mis-matched/mix-&-match calipers & forks, normally you've got to make some very special billet caliper hangers. And again, with the sliding calipers that's a pain in the ass. Folks GO with the opposed-piston type of stuff precisely BECAUSE of the simplicity of mounting the caliper to it's hanger. However opposed-piston calipers don't always FIT with wire-spoked wheels, due to the spokes lying further outboard of the wheel's radial center-line, than do the solid cast/mag WAGON wheels. So often as not you wanna use the sliding calipers with the wire-spoked wheels because otherwise you're gonna make contact between the caliper & spokes. Of course, it's gonna fit easier if you use a larger rotor, 'ause further outboard towards the rim, the spokes are narrower etc. So that's the first place I'D start on that one. A smaller diameter rim, 18" always better than 19" for several reasons of course - but 17" if necessary and possibly even 16" for a VF750F or Freddie Spencer AMA Superbike type of "stance".
I've been thinking of building a spare front wheel for the CB900F "CB900K0 Bol Bomber" out of a spare rim from my "KZ440LOL" project, a 3.00x16" Borrani or better still Super-Akront 3.50x16" if I can find one for a good price - that's a REALLY nice rim by the way. I've got a 3.50x18" to work with, and I've HAD the 16" version but lost it in a fire. Was NOS too just a beautiful rim. Would make one awesome front wheel IMHO.
I'd like to do something similar with a tube-framed VF the V30 Magna or a shaft-drive VF750S or VF1100S Sabre even - Magna perhaps too - as an homage to the Czechoslovakian Grand Prix racer the "CZ Type 860" the air-cooled V-four such an awesome bike - but I'd wanna do 'em up in proper '80s tech with the 41mm TRAC forks etc, and 18" rear rims with 16" fronts - a faux-drum with CBX550F converted Comstar hub with internal disc brakes - better still something similar from the PC800 Pacific Coast & GL1500 parts with all custom-made rotor shrouds, etc. 3.50x16" with the "spare" 4.25x18" rear rim for Radial Sport-Touring tires, or 2.15x16" WM3 or 2.50x16" front just like the original Comstar front wheels, with a 3.00x18" Borrani or better still that 3.50x18" Super-Akront rim with the original Bias-Ply tires. A 2.15x16" flanged Borrani rim would be so super light-weight. With a chopper type SPOOL front hub, and perimeter discs attached to the shoulders of the rim itself. Now THAT would be worth screwing around with custom caliper hangers. On a 16" front rim, a perimeter disc doesn't have to be all THAT big, so this would be the ideal most light-weight version Maybe even with some of those tiny single-puck calipers from the CB350F/CB400F etc. For the CZ replica I'd also like to carve right into the engine itself, cut grooves all over the water-jacket so that the surface area increases, and then the radiator could shrink down to that of an oil cooler or a dirt-bike sized radiator etc. So that the heads would show up better, show off that V-four engine the same way the CZ did.
Would love to do a replica of the Jawa 350cc V-four racers too, based on a Honda MVX250F V-three. THAT would be one cool retro-fried café bike as well.
The main thing being, these are all TUBE framed bikes. The VF750F would be perfect except for the fact that it's frame is square tube steel and very much mid'80s style - no way you could make that look like it belonged on the Grand Prix grid circa 1965 - the CZ was a serious contender, right up there with the Honda and MV Agusta multi-cylinder bikes. It just didn't have the same level of SUPPORT as those other marques had. If the Eastern Bloc had any interest what-so-ever in promoting better technologies - well they DID have the Lunakhod moon robots and the Buran pilot-less Space Shuttle, YEAH - but they undermined the likes of the TRABANT automobiles and when it came to the CZ motorcycles they wanted mass produced tough utilitarian transportation but nothing more than that. Miraculously, the URAL folks actually produced limited prototypes of a DOHC-four racer in the vein of a Gilera Rondine slash MV Agusta etc. But again it went nowhere. The CZ on the other hand, was simply a labour of love where engineers and fabricators volunteered their own time to their own pet projects. These would've been guys who remembered pre-war Czechoslovakia and it's pre-eminence over the world of mechanics and technology. Friggin' AMAZING Grand Prix bikes it's as simple as that. If they'd been able to scrounge up the support of some SMALL Western sponsorship, they'd have cleaned up and today we wouldn't even KNOW the names of Giacomo Agostini or Mike Hailwood! Seriously - and so methinks it's very fitting, yeah it's a Honda, but the VF750F Interceptor and it's ilk was the first V-four sport-bike to come along in the wake of the CZ so in that sense it's like the GAWDFODDER of the Interceptor, there's some genuine connection between the two. It would be pretty damn cool. Even done up as a Honda maybe with the designation "CZ860" ha-ha. Would be even better if the 750 could have an 860cc over-bore job done on it....
But that's a long way off. I'm just contemplating a 16" front wheel on my Honda "CB900K0 Bol Bomber" right now. I might just try out the KZ440LOL front end on it, for shitz-&-gigglez, as it's a 39mm CB900F fork with the 4LS Suzuki drum adapted to it and a 3.00x16" Borrani rim - might be fun to swap out the fork tubes and stick the 16" front wheel onto the bike. Obviously the BRAKES would suck ass on the big heavy assed Honda four. Wouldn't even try it on the CB750K DOHC - maybe a Fontana 250mm 4LS on a light-weight CB750K/CB750C single-seater café. But not on the bigger faster 900cc. Which in this instance is stuffed full of a Wiseco big-bore kit. Not sure which one, but the point being that it's tweaked out, and NEEDS it's current set-up of 296mm CB1100R type vented double-thick 11mm rotors, CBX caliper hangers, etc. Even the 286mm brakes of the GL1500/PC800 Pacific Coast aren't up to that same spec. But they might work as well with some Cast-Iron replacement rotors in there, water-jet cut to fit. Better friction co-efficient than the stainless OEM discs.
Even so, with or without the brakes, the 16" rim and tire alone would give some sense of ho the thing old handle, without screwing around too much. Probably easier to pop a 16" Boomerang Comstar in there. But the 3.00x16" with low-profile 110/70-16 tire would be a better match for the 4.25x18" and 160/60ZR18 I'm trying to throw together.
Thing is, as soon as a person's messing around with different forks and more to the point different swing-arm, there are other hubs available for this type of thing. There are various GSX-R swing-arms available which utilize a 17mm rear axle, and there are some light-weight rear disc hubs such as Yamaha TDR250 which normally uses a 15mm rear axle but a bearing swap would enable 17mm axle to work. I believe that's a 36-spoke hub too, so the cheaper Super-Moto rims in 5.00x17" & 5.50x17" would lace up to it. Meanwhile the later GT550 & GT750 hubs have only 36 spokes to they would work with the super-moto rims yet otherwise are very similar to the Honda hubs.
Getting into the other FORKS of course, there are larger FRONT axles as well. The GL1500/PC800 fork has a 20mm axle, and some of the more modern forks are even bigger than that like 25mm - there are a few builders have modified the SOHC CB750K & GL1000 front hubs to work with 25mm bearings etc. So I KNOW it's possible. I only hope it's gonna be a simpler matter to adapt these hubs to the 20mm axle of the GL1500 forks etc. Hopefully just a bearing swap. Of course, I really wanna use the PC800 "hub" anyway - IF I can get it laced up to wire spokes etc. And with the straight-pull "nail" spokes, it might be necessary to drill the hub differently for an 18" rim vs a 16" rim, or 17" even. This FAUX DRUM is gonna be a pain in the ass in the first place, but yeah the rim size is gonna have to be a fixed value. Changing the rim would mean modifying an entire extra hub and calculating an entire new drilling pattern. UNLESS of course, it's possible to lace up some bent-head spokes to the thing? It's all on paper at this point, while I'm waiting on Kijiji adverts asking for a GL1500 and PC800 front end. Get my hands on a cheap PC800 wheel, and I'm chopping it up in the first five minutes.
WHATEVER - you were originally talking about the COMSTAR wheels. Check out the rebuilt Comstars from the likes of MELCHIRO etc, and there's a 1976 RCB racer being rebuilt on Facebook no less - over in France there are guys building replica wheel sets nice fat 18" & 18" silver Comstars using CB400T & CM400 wheels with 2.50x18" rim from CB900F rear wheels, or better still 2.75x18" from the pro-link CBX rear wheels - with 3.50x18" or 4.25x18"-5.00x18" rebuilds of the rear SILVER Comstar wheels, first generation preferably. Some really cool stuff - some of 'em have even figured out the Rivets with the "HONDA" printed into both sides of each rivet. REALLY cool wheels.
I figure a really good place to start would again be the smaller rear DRUM brake hub versions, the CB400T REAR Comstar, so as to replace that hub with a lump of Billet, or an insert-type rear disc conversion like they used to sell for the SOHC CB750K in the early '69-'74 era before the CB750F1 came out. 'Cause it's really important to minimize the weight of that rear hub! If I could get my hands on some nice lumps of billet, get 'em machined how I want, I'd build a CB400T rear wheel AND an XBR500 rear wheel, with the widest possible rim on 'em. So long as it's not a super complex thing like the "Front Hub Trick" that I'm always gonna wonder whether it's gonna FALL APART while riding the damn thing. I like the idea of an insert-type disc brake adapter on a smaller rear drum hub too. Just so long as the hub itself is strong enough for the extra-heavy-duty spokes, it would be preferably to use a 140mm drum or 160mm drum - 180mm even, rather than the enormous boat anchor of a 190mm CB750K rear drum.
Same deal with the Comstar - and what you wanna do is outfit the thing with a 2LS linkage to get maximum efficiency from that rear drum. Take the CX500 for instance, it's got the shaft on the right and drum on the left - well there's a 2LS shoe plate available from the CB72/CB77 I dunno whether it's the right SIZE per se, but it's on the right SIDE or left side to be specific. 2LS and 4LS shoe plates only run in the one direction, they're worse than SLS when you run 'em in the wrong direction. Now - THAT being said, when it comes to the smaller drums there are all SORTS of smaller 2LS shoe plates some of 'em are Magnesium even - on the '80s MX-ers especially on front drums little conical hubs etc. If you can find one that suits the rear drum - there are 200mm right-side 2LS plates on some '60s era Yamaha YDS1 type of bikes, so THAT might work on the 190mm rear drum of the DOHC & SOHC Honda CB's - the only problem being that Honda rear hubs are just about the only 190mm drum brakes out there! It's FAR far more likely to find an MX front shoe plate in a correct size for the XBR500 or CB400T rear hubs because they're around 140mm or thereabouts. THAT'S a possibility.
MAGNESIUM plate & 2LS actuation,, light-weight 140mm drum - and bump out to a 3.50x17" rim - if ALL of these things could be brought to bear in just that ONE rim - not to mention it being a BOOMERANG Comstar rim - now we're talking! It's just gonna take a whole lot of mix-&-match to figure out what's gonna work. And the chutzpah needed to rebuild the wheel with a swapped-out hub!!!
-Sigh.
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ive got the front but am still lookin for the rear..
