I noticed something mentioned in this thread that may be unsafe, and thought I'd dig up this thread from the abyss to add my two bits. The one fellow mentions picking up a "wider" sprocket carrier for clearance. If just that is done, there will either be a problem with the chain line or the wheel alignment.
That said, there are ways of moving the chainline left. A few fellows on the CB1100F.net forum mention welding a new sprocket onto a ground down center off an old sprocket, yielding an offset. There are several stock sprockets that fit the DOHC bol d'or bikes' layshaft splines, such as RC30, VFR, CBX etc; that all have a certain degree of offset. I'm sure there's something like that for the SOHC hondas as well. One guy I know paid a couple hundred bucks, keep in mind the front sprocket is a consumable, for a custom ground offset racing sprocket from an e-bay seller in Deutschland. one cheap and non consumable, needing to be done only once, is to mill down the surface on the sprocket carrier, just to match the wheel of your choice to the sprocket of your choice. I think the sprocket carrier swap is a brilliant idea to widen the chainline, but there is more to it that must then be done. You can throw a nice wide tire on one of these bikes. It's not impossible to put on CBR wheels, though probably easier on the DOHC. The swingarm clearance is an issue on stock swingarms, but it's not really hard to swap out to a swingarm off an early model ZX or something like that, yielding a superior swinger to any of the CALFAB or Dresda arms, at pennies on the dollar. The brake torque arm on many modern bikes is in the form of the brake carrier simply being bolted up to the swingarm just ahead of the axle, rather than a long heavy piece of steel like on honda fours. Ducati did it that way years ago. So you needn't worry about the arm, if it's all going to fit within the wheel diameter anyway.
(But if you're gonna build up a custom torque arm, take a look at some of the ones on tube framed bimota's, I think the SB3 is one example. They are hollow and carry the brake fluid through them rather than having a brake line zipped on top. I'm trying to find fittings to make one such an arm from a segment from a modular lamp made by ikea. Wish me luck ha ha. Just need some custom sized banjo fittings and a couple of clevises on a pair of banjo bolts with the right sized thread. Maybe just a bolt hollowed out in the fashion of a lightened racing bolt? Perhaps it would be easier to source a different hollow rod for the arm. The ikea stuff is strong though, and I have ten of them....)
Yeah, anyway, if you're really fixated on putting bigger rubber on your CB, you don't have to do it the way it was done thirty years ago, not anymore. Nothing has to be done that way, not when it costs less to do it better. You can have better rear-sets than Dunstall made for pennies on the dollar (recently saw NOS dunstall rearsets go for $700+, for a CB250!) just take some stock pedals off of any old plastic rocket and you've just got to cut and drill a pair of plates to bolt them where you want. A lot of stuff off of nineties era sportbikes is dirt cheap right now because nobody is "into" them at the moment. So there is decent stuff that can be fitted up for cheap.
I don't think that Buchanan's is the only place to buy rims these days, there's money to be saved looking into the Harley stuff. But Buchanan's lists the service of cutting and threading spokes for you, rather than making a custom set for an extra hundred bucks, if you want to fit a different size of wheel. In light of that, your 2.15 X 18" rim sounds like a winner for a front wheel, on the scale that they used on CR750's, which makes your steering a little more sporty. There are 3.50" rims made for rear wheels in an 18" size that would fit front wheel low profile tires of the same spec as you see on the modern bikes, with 120/70x18 width that easily would fit between your forks. So too a 4.50" rear Harley style steel rim, either an 18" for the tires made for the likes of sport touring Beemers of ten or fifteen years ago, or a 17" for better tire selection the like of which you see on ten year old mid sized sportbikes, yielding a 160/60 tire.
(The smaller rear rim would also, in combination with a longer pair of shocks, perhaps even a mono-shock conversion, yield a better angle for the swingarm due to the drop of half an inch. This would fight the tendency to squat under acceleration. It could work well with a longer swingarm too. A little bit of the classic look is lost though, and I think the 18/18 combination gives the best look, just as you see on the CR750's. Such performance vs appearance choices are unavoidable, such as whether to go with a four into four, or shed forty pounds and go with the four into one pipe. Take that a step further though, and why don't aftermarket pipes have an EXUP valve yet? Surely that would be a cheap performance upgrade with an easy tachometer pick-up and programmable rate. For the price of some classic CR racing carbs and a dyna ignition set up, you could have a junk yard EXUP with a controller, and get into a micro-squirt and some second hand throttle bodies off a 600cc ninja.... Ahhh, but I digress. One day somebody is gonna make a killing building a direct injection head for the SOHC 750, when the cult of that bike reaches the level of the custom alloy overbore heads available for Norton Commandos. The entire Norton, so too the Sunbeam S2, probably a Vincent black shadow soon enough, the Nucklehead, all are being built new today from catalogue parts, one day so too will one type of honda or another. I am betting on a hollow shell engine filled with batteries and a high torque electric motor in a carbon fibre frame built to look like the CB on the exterior, coupled with discrete sub-woofers disguised as exhaust pipes and sampled digital CB engine sounds throwing just the right rattle through some tweeters to mimic some slightly loose valves, all variable through an ipod with an option to make it sound like a galloping horse, that's gonna be the hot set-up in about fifty years, but who knows. Maybe a plain old horse will be the hot set-up in fifty years. Maybe the triumphant cockroaches will one day build themselves little rollerskates. What a tangent. )
120/70ZR18 and 160/60ZR18 are the specification on 90's era ZX1000 type bikes as well as the Beemer sport tourers of ten years back, meaning tires will always be available given the longevity of the beemers crossed with the wealthy demographic who own them. This is one reason I like this tire choice. 17" tires fit more bikes even than the stock CB tires did in their day. They just look stupid, that's all. There is a limit to how fat you can make your tires, and that limit is good taste. Go too far and your bike starts to look like an Orange County Chopper. Nothing wrong with that. Some guys like Tacos, other guys like Hot-dogs, if you know what I mean. I draw the line at 120/70X18 and 160/60 X 18" tires. And I draw the line at a well prepared tofu burrito.
I think the Harley aftermarket steel rims, all of which you can get for under a hundred bucks a piece, may require a set of larger nipples, again from Buchanan's. Spoke nipples that is, not talking about food anymore. That's about fifty bucks a wheel. But one source I think should be tapped, for alloy rims, are all of the cast wheels out there that could have their three spoke blades chopped out and milled down, and then be drilled with a decent pattern. It sounds dangerous, I know. But they've got five times the alloy on those rims as they have on a typical alloy rim made for spoked wheels. And, they're in all sorts of sizes and come dirt cheap in many cases. But in any case, cheap aftermarket stuff for Harley yields some decent steel rims for a much better price than three to four hundred bucks each for alloy rims from Buchanan's. I see them on fleabay for as low as fifty bucks on up to a hundred. If you don't mind skinny stuff, GL1000's and CB750A's had alloy rims at the same spec as you'd find on late model SOHC 750's. The DOHC 750K has some decent width stuff, with I think 2.15 x 19 and 2.50 x 17" rims, steel, but fatter wheels that bolt straight up to the SOHC K, though I hate to see a DOHC K chopped up and sacrificed. If you don't mind the look of the engine, it's got the performance of a bored out SOHC engine with cams and a pipe. And you can throw an 1100 in there as it is, so the DOHC K is a pretty cool bike. Anyway, it's got wheels that are fatter than the stock SOHC.
For spoke wheels on my DOHC CB750FC, (those comstars are heavy sonsa#$%*es get rid of them if you have them!) I've elected the GL1000 front hub, and the KZ1000 rear rather than the more expensive due to you SOHC 750 types, SOHC 750F SS rear hub, and the front goldwing hub is also the hub of choice for a dual disc on the SOHC Honda 750. But you don't have to go with the goldwing front end to use that wheel, just because the calipers would line up. The hub can be mated to fatter rim and rubber, as well as a pair of floating discs off a CBR900RR or other CBR or six bolt disc. Many have successfully used discs of any old type by having a new bolt hole pattern drilled and the center hole enlarged to fit. That might cost a bit, but widens up your options. The goldwing hub comes with a small spacer normally on the outside of the brake disc that can be used to push the discs further outboard. With the floating discs, any old set of four pot or six pot Brembo, Tokico, etc calipers can be spaced correctly with a bit of alloy plate and a little help from a local machine shop (You could use the cut off from the rear-set mounting plates.) they can be bolted up to any set of forks you want, mounted up with a set of tapered roller bearings which you were gonna put on your stock CB anyway. You might need to press out a steering stem to put into the new triples, but that's not the end of the world. Just think of all the 41mm and fatter forks out there. I like the stock Cb forks and triples myself, and if you do too, there are great ones for dual disc on the DOHC 750/900's or even the VF-R's. Anyway, what I am getting at, is that all of this doesn't have to cost more or be any more complicated than, say, rebuilding a set of stock CB forks, polishing the triples and sending your single brake disc off to be drilled and planed flat, fitting a dresda arm, a pair of Akront rims and Dunstall rearsets, kits for caliper and master cylinder at fifty bucks a pop, swapping out sprockets to fit a 130 tire, etc.
A guy could spend an arm and a leg building a sporty version of a CB750 to the standards of what they were at thirty or forty years ago. A whole cottage industry has sprung back to life to suit their tastes. But look at what's available on fleabay with a creative eye and a can-do attitude, and you could probably do a whole lot more for the same cost as the classic parts you were gonna use anyway. I'm not advocating the bike lose it's classic look, the whole CB/UJM vibe is the whole point of it, now that these bikes are no longer as cheap as they were. I love the classic look and I'm trying to apply it to my DOHC F bike, candy paint polished alloy spoked wheels and all. But when it comes to the stuff I have to replace anyway, I have an open mind as to how it can be done better.
So I think it a bit remiss to point out to folks that a Dresda swingarm would allow a fatter rear tire when a swinger off a late model bike could do all that and more for waaay less money.
Parts that don't seem to fit can be made to fit, with different sized bearings for example there is no reason why a wheel swap has to follow the same diameter of axle as a guide. With a bit of help from a local machine shop which you can pay for by not paying for those premium classic aftermarket re-released replica parts, not to mention the advantage in affordable, available machine tools in your average garage compared to thirty years ago, you can fit together anything you want. That's the main reason old school builds were concerned with what "fit" together, they only had socket sets and electric drills to do the job with. What a typical middle age guy has in his garage today compares favourably to what an independent race team had back in the seventies. We may never have what Honda had in the 60's, maybe with rapid prototyping and a sentient computer, one day we could match that.
But where the shade tree mechanic is at now, at least we have wound the clock back to where we have what one of the independent CR750 or RCB or RSC racers had on hand. With money for some CAD/DAM and mill-work, who knows what we could all accomplish with the pool of knowledge available at a keystroke. Yet, I am more than pleased with not having to settle with the adverts in the back of chopper and cafe racer magazines, and what was available at the local hardware store, as was the case a generation ago.
What a mistake to emulate what the shadetree mechanic did in the 70's when you could do what a sponsored race team could do back then instead!
-Sigh.
