79 CB750K RCB Clone-ish. On the road.

Basement rat

Over 1,000 Posts
Re: 79 CB750K RCB Clone-ish. Stretttccchhh the tank.

Been away, a few updates.

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It will be done with paint and a much better bracket system for the fairing. I might even make a new windscreen. I cant stop anywhere without people walking up and asking questions about it.

So far I have about 500km on it and my longest single ride is about 150KM/ 100Miles. After about that long, the seat gets a little hard. I might get some padding for it.

I have done a little work since the last picture, adjusted the lights a little, changed the battery/ location, trimmed the fairing a little for hand clearance and other little things.
 

SoyBoySigh

Been Around the Block
I love it. It's great - if you wanna upgrade the front end to a dual disc, maybe throw some alloy rims on the thing, I've got a bunch of parts kicking around from my own former CB750F now CB900F project. You can get revenge on me when my own build thread gets started up here. But yeah, if there's anything that bike now needs, it's a beefier front end and upgrades to the brakes. My own 900 here, I've got the 39mm obviously, I've got a spare 39mm that's going on the "KZ440LOL" I'm building for my kid, but yeah down the road I wanna throw a hybrid GL1500 front end onto it, possibly with a set of yokes from VF1000F or thereabouts, depending if the width is still all there. Gotta CB1100R gas tank here, chroming up the sides for rubber knee pads & wing badges, doing an homage to the CB450K0 Black Bomber - the "CB900K0 Bol Bomber", and I'm thinking the upgraded GL1500 front end - 20mm axle 41mm fork tubes integral fork brace TRAC anti-dive, 296mm rotors etc etc - could be turned into a wire-spoked fake DRUM-brake in the vein of what folks are doing with the CBX550F front Comstar hub with the internal discs. With different shrouds on the sides the GL1500 "hub" or better still the PC800 Pacific Coast donor wheel "hub" - could look like just about any drum brake you want it to. The GL1500 rim has that massive outer ring structure which makes me think of the cooling fins on the Munch Mammoth's 2LS hub. Though the PC800 looks easier to convert, possibly a smaller outer diameter etc. But yeah, for the time being I'm throwing on a CB750K8 front hub with some rotors from CB1100R & CBX caliper hangers, I've got all sorts of alloy rims for it 2.50x18" un-marked Borrani from Harley Iron-head sportster (cost me $50 delivered so I bought two of 'em) and a 3.5x18 Super-Akront which was already drilled for a KZ1000 hub - either the drum type in which case it'll fit my SOHC CB750F spoked rear hub which will fit the CB900FA rear rotor OR the conical KZ1000A/KZ750B rear hub which fits the Comstar front rotors I'm thinking of the early SOHC Comstar discs they're smaller) I've got a couple of 40-hole 17" rims too (they might be on sale still cost me $39.99ea so I got a 4.25" & a 5.00" now THOSE are some rims which would work great on the CB750KZ, hey? I'd bet this here spare Harley 2.5x18 & either of these 4.25 or 5" x17" rear would BOTH lace straight up to your bike no problem. Well actually they're both drilled for Harley hubs, so they'd need to be re-drilled at Buchanan's.... But I'd wanna see you use a proper dual-disc HUB too. I'm thinking I ought to swap my own plans to use a GL1000 hub so I can use the CB1100R vented 296mm rotors without modifying the carriers. For my GL1500 front end, I've scored a non-drop-center 3.00x18 & I was planning all along to use 4.25"x18" for a rear wheel, for radial tires in introductory/minimum widths. My CB750F was lost in a house-fire just over a year ago, but I've got this fantastic CB900F now it's got all sorts of fantastic bells & whistles on it, even the Bol D'Or Super-'F crowd approve of it. Though ... maybe not what I'm DOING with it. Ha-ha.

Your bike looks fantastic it's what people should be doing with all of the CB750KZ's out there ... well okay actually I've seen some pretty fantastic café bikes too.... But they need at the very LEAST the 37mm dual-disc front end, they need a double-sided wire-spoke front hub - the GL1000 should be easy to modify for the five-bolt rotors, though there's more to it than just drilling more holes take it from me. The SOHC rotor carriers could be un-riveted to the discs, and CB900F rear brakes OR these here CB1100R / CBX pro-link / GL1100A Aspencade 296mm vented rotors could be riveted to the SOHC carriers, or bolted together just like the equivalent '70s-era Yamaha rotors THEY had nuts & bolts on their brake rotors, plenty of folks have done it. Well, maybe I'd feel better with new hot rivets....

But yeah, I think the bike needs wider alloy rims on it - and didn't I just mention how cheap it can be to purchase rims? It's mind blowing. Even my 3.5x18" Super-Akront only cost me something like $40 you've just got to keep your ears open for the right ones.

If the RCB were to be made super duper accurate, then it needs a CM400T front wheel that's a non-reverse-Comstar type though it's painted black some silver spray-paint and it looks exactly like the RBC wheels ... either a rim swap with nuts&bolts instead of rivets or replacement rivets like the French RCB enthusiasts are building such wheels with - the rear wheel could be a regular silver comstar widened, weld-up Kosman Industries style, though really those RCB wheels used a different hub which could probably be made from a hunk of billet and then it looks REALLY authentic. I wonder if the 17" GL1000 silver comstar rear wheel would be closer to the proper proportions - somehow welded up to an 18" rim though ... there are a BUNCH of folks on the European 'F-orums who know a heck of a lot more about it than me that's for sure. But yeah, IF one were going for a replica the silver comstars are the way to go, with the CM400T front wheel for the correct 18"diameter - fore & aft.

But if it's all about PERFORMANCE then wire wheels are where it's at!

And if what's more, the whole damned bike is about performance, and not just looks - I'd suggest the gas tank be stretched in the usual fashion, using two entire tanks cut at different points and then welded together. Even if that façade over the rear of the tank did hold gas, it's got to add a bit of weight, right? It could really become quite the tank if it were stretched back to the point of a CR750's ergonomics. Another thing that's interesting is the way you've fitted the headlights so far forward of the fairing's bulb openings. Whether you stick with those same bulbs, or possibly use some smaller projector beam bulbs like I'm using, there would be that open space where the air is flowing through. It would make sense to throw an oil cooler in there somehow - the 900 pump and sump, path plate etc are all you really need, or rather the pump and path plate (unless your 750 already HAS the correct path plate - speaking of which I've got a spare one of those on hand too, though sadly not the pump anymore) the 750 sump can be drilled I modified my own on my old 750, I even sandwiched up an extra layer from a spare sump for a special deep sump it's a good mod it's being done on the CB1100F.net 'F-orum at least a couple times now, [but I thought of it first!] then it needs a modified pick-up screen but you want that ANYWAY 'cause it prevents cavitation and total engine failure) the sump can be drilled and threaded for very simple hoses and clamps this is how it used to be done so WTF - then a simple cheapo oil cooler with clamps on hose barbs and you're done! No NEED for those fancy schmantzy AN- fittings which only look like crap IMHO unless they're electroplated in Nickel finish - the blue & red anodized ones are Butt-Fugly IMHO - drilling the stock sump, some brass hose barbs some cheap hoses some holes clamps and a cheapo oil cooler or transmission fluid cooler from a truck let's say - the only serious investment here would be the modified pick-up screen from the CB1100F-net 'F-orum and the 900 pump itself it's an awesome mod and yeah I feel it's a must for the 750 while others think the 750 doesn't need it I've had one overheat and die, it just depends on how hard you ride 'em and in what weather. Up North we may have winter, but our summer days last up to 24 hours, you get some ridiculous temps and some looonng "Iron-Butt" touring days. Mmmmmmmm..... But yeah - the 750 SHOULD have an oil cooler. Just don't go thinking it's got to be expensive! So yeah - that could be fitted up inside the fairing, right behind those headlights. Some fiberglass or pvc/abs sheet could be formed so as to duct that heated air out the sides rather than blowing it down over the motor or up in your face. Maybe some duct vents for colder days at the end of the season? Hmmmmmm....

So yeah just saying them two headlight openings could serve quite a purpose. That's all. And I'm not knocking the super-fine bling-bling hoses that people are selling on the 'F-orum I'm just saying there's a different aesthetic and if a person's shooting for a '60s-'70s style bike, it doesn't hurt to use the threaded hose barbs plain cheap hoses and stainless hose clamps. It can even lend the bike some retro-cred!

And what about the CB900F2 fairing bracket? Or even just welding a threaded bung onto the neck of the frame, so a pipe can be stuck into it and run forward to the lightbulb area? I'VE got a fairing now too, a Ducati 900ss bubble type half fairing, and I've got to figure out which of those methods is preferred here. if YOU did it first well I could copy what you're doing. Only thing, sure as shit I'm not welding struts onto my gas tank. Especially not the alloy CB1100R tank. I'm planning to make copies of this tank, I've got to keep it pristine. Once that happens I can chop the living hell out of it. But not before. Ha-ha. Seriously though - it's got to make for one serious hassle when you need to get the tank or fairing off of the bike, dunnit? I figure I'm going with the OEM fairing bracket for now, just 'cause it's the most sturdy & should hold up to the wind. But it's still gonna get chopped down a whole bunch, if for no other reason but that it's not the correct fiberglass for it.

Oh well - just my two cents again. But I would like to offer help if you're into swapping out to alloy rims. If nothing else, here's the link to where I got mine. I should buy up a whole lot more:

Because I wanna do Weld-Up rims, based around boomerang Comstars, 2.15-2.50x16" front (the one with the smaller standard, non-spider type hub!) and 3.5x17" rear boomerang from CBX750F & VF1000F European Bol D'Or models, and I've got a 2.50x18" silver boomie from a Euro spec CB900F I wanna pair that up to either a 3.0x18" from the same bike OR the black wheel from CBX750F etc 'cause they've got a smaller rear hub & that makes for the lighter wheel etc, lighter smaller rotor too - I wanna weld 'em up to 3.00-3.5x18" front and 4.5-5.0x18" rear. Then stick EITHER pair onto the new CB1100 - with a copy of my CB1100R tank right here, modified in the tunnel to suit the new models of course - make an '81-'83 CB1100R replica based around the new 2010-2014 CB1100 and watch the sparks fly - which is to say take about three hundred pre-paid orders from Japan alone! Seriously. They don't have a whole lot of performance upgrades for the new bike yet, but it should at least LOOK the part, even if it can't hold a candle to the original! Ha-ha. I think there's gonna be a huge market for that type of stuff. Just sayin'.

Maybe then down the road, somebody could make a frame kit for the '07 Tokyo Motor Show prototype? Down the road. In the MEAN time, the earlier version is best because it can be built around the stock frame it's really just a body-work and wheel swap. A no-brainer.

YOUR bike is a much more ambitious build though. The RCB was radically different than the DOHC street-bikes. There's a French company making fiberglass TANKS in the early RCB style, I guess if you found your fairing you're already onto that.

You know what's needed, that I haven't seen anywhere? A replica fairing for the Magni-Honda MH900. Pretty close to the Ducati item, but much much more suitable on the DOHC-4. Wouldn't take much to turn a bone-stock CB750K or CB750C into a Magni replica, it just boils down to the rear-sets, the side-covers, and that fairing! Even Magni themselves don't sell it right now. Well - there's this new Magni BSA triple in the magazines, maybe THEY know where to find one?

-S.
 

Basement rat

Over 1,000 Posts
Thanks^

Its not an exact clone, its just inspired. Style wise I prefer the wire wheels. Im researching passivley on a gold wing swap or something with spokes and dual discs. I can lock the rear by stepping on it hard enough, so its not the end of the world. The oil cooler is on the to do list.

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Here it is.

My little Miss here is part of the reason its been so long. That, buying a house, married and etc. I still have a few little details to finish like sewing a seat skin, but its as close as its ever been.
 

biker_reject

Over 1,000 Posts
OMG, you're done! I finished my DOHC last year and have been riding it working all the bugs out. I beat you, but I started two years before you and built three bikes in between then. I also had three kids, a house move, and two jobs since I bought my donor. Congrats and it looks great!
 

biker_reject

Over 1,000 Posts
http://www.dotheton.com/forum/index.php?topic=9860.210


https://www.youtube.com/watch?v=IKV6MZz8fzU
 

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biker_reject

Over 1,000 Posts
I shortened it with a Progressive kit and still had to drop it through the trees! Wait, do mean the fender??? Yeah, I didn't quite know what to do with it. Years ago, I bobbed it and had a dude shot peen it and I liked it and all, but I hated how high off the tire it sat. I knew huggers are a pain when gravel or pebbles get sucked up into them, so I did a slight lowering of the fork brace. I like how it turned out. Since I used button head screws, I can take the fender off if or when I get tired of looking at it!
 

SoyBoySigh

Been Around the Block
Okay so ya'll have turned this into a contest then? Well - He who laughs last, laughs longest! Ha-ha. My "CB900K0 Bol Bomber" is still waylaid by budgetary constraints and all sorts of other B.S. - But it's still gonna blow those two bikes outta the friggin' water. 'Nuff said.

-S.

POST-SCRIPT:

These ARE still probably two of the top ten most gorgeous DOHC-4 builds of which I am aware. I chalk it up to the retro-fried & period-correct factor. All of the "up-dated" bikes with the later crotch-rocket parts, which might have taken the world by storm some 10-15yrs ago, they all look like shit now, don't they? I mean, not just to ME - 'Cause I didn't like 'em all along! Was rapping at the 'F-orum as far back as '03 that 'F-olk needed to put the brakes on all of the modernization schemes. If maybe ONE 'F-er listened to me, then it was worth the time. But yeah, you guys are gonna love the period-correct style suspension & brake upgrades I've been cooking up for this thing.....
 

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