The DOHC-4 cranks were 69mm stroke, iirc.
Like I sez, I was always more interested in a SHORT-stroke motor with the 73mm pistons from the 1123cc kit mated to a CB750F crank, for a sub 1000cc displacement that would allow unrestricted diameter carbs in AHRMA "Forgotten Era" - The shorter stroke should help spin things up faster, maybe even keep the piston speed down to the point you can run a much higher RPM than otherwise?
Well then again if you check out Brent "Captain" Hyde's bike, the 69mm stroke doesn't seem to be a hindrance when he's pulling stumps with a 150+RWHP thanks to an original factory race-bike PLUS an extra 40yrs of development....
Even so, yeah - I should think there ought to be some application for a stroke length midway between the 63mm & 69mm OEM cranks?
One has to wonder at the possibilities, where if you're boring out the top crank-case AND going with a custom billet block, AND a custom crank, new sleeves in the block, etc etc - What all might be done if we changed the barrel-to-barrel SPACING? Move the two outer cylinders slightly further outboard, and think of how the bore might stretch even bigger still! Yeah, the valves might have some difficulty lining up - But since we're really only talking about a matter of mere millimeters, one has to wonder at the possibility of a larger valve guide being reamed eccentric to the outboard, and that bigger diameter valve guide needn't be all THAT much of a hindrance not of we're talking about a fully ported head. Right? I mean, YEAH - it's a whole lot more work. Pretty outrageous stuff.
Dunno whether the crank already EXISTS with the standard main bearing spacing, yet with the two outer rod journals spaced further outboard. The most ridiculous thing you'd have to do would be a PRESSED-UP crank, with or without roller bearings shoehorned into milled out crank-case journals - Of course since we're only talking about a couple of millimeters, it MIGHT be feasible to grind out a couple of mm's to one side or another - Surely the crank webs wouldn't be TOO thin at that point?
One way or another, SURELY it's FEASIBLE somehow? Expensive as hell, yeah. Perhaps as a pet project for some wealthy "captain of industry" in the engine building racket? Ha-ha.
What all would you need? However many mm's you expanded over the current max bore, you'd need HALF that for the off-set, correct? So if you're talking about a 75mm bore you'd go outboard one millimeter? 77mm would require two mm's? Not only for the crank, the block, but also the valve guides?
Gotta wonder what the new theoretical limit might be. The holes carved into the top case, however much material were left on the top face? The gap required for the cam-chain tunnel & the tensioners fitted within with their roller pins? The crank webs themselves? The included valve angle? The exhaust ports?
From what the aforementioned DOHC-4 monster tells us, it would seem like you sure don't want your inlet tracts to be even MORE twisted out of the straight through & through. If you can't build the exhaust outlets and carb inlets far enough outboard, so as to run everything straight as the crow flies, well apparently THAT's the real limitation on power production - or so I'm told.
IMHO, there's a lot of potential in adding fins to the outer walls of the water jacket on a later era liquid-cooled motor, making retro-fried side covers for 'em, maybe a nice polished round-domed valve cover - something which LOOKS for all the world like the SOHC-4 series, but which is really a CBR954RR engine at it's heart. Or a V65 Magna with a shaft-to-chain conversion ala Magni MV-Agusta or Yam' XS-Eleven, etc etc, done up as homage to the Cezeta CZ Type 860 - Or a copy of the CB750P7-ii 5-bolt dual-disc 40-spoke front hub, along with a wire-spoke conversion of the 5-lug COMSTAR rear hubs to effect a wire-spoke conversion on the GL1100 & GL1200 BIG 'WING and then grab some sort of BEEMER race fairing, move the cross-brace on the swing-arm for a taller rim & tire, and thereby whip up a bigger displacement version of the Doncque DLF-1000 Endurance-Racer!
Well either which way, yeah - I think there's massive potential in doing the retro-fried treatment on the later era motors, in addition to the expected bodywork & running-gear etc.
As for the SOHC-4, I should think the missing element isn't so much in the motors as the CHASSIS - If we could have a decent batch of EGLI replica frames, or more to the point the twin-shock "spine" type frame from MOTO-MARTIN. But above all else the Akront "NERVI" rims for some rebuilt COMSTAR wheels, half the weight in equivalent sizes, available in any width you could possibly dream up for a SOHC-4, all the way out into the 6.0x18" type of stuff which barely looks sensible on a CBX six but let's say IF you wanted something that ridiculous on a SOHC-4 you could have it, or COULD'VE had it, if only we'd begun to rebuild our Comstar wheels BEFORE they were yanked from production! Yeah, if we can get the MORAD people to bring 'em back, we could do some truly awesome stuff with the SOHC-4, get 'em around the track a whole lot quicker.
IMHO a really important part would be a 296mm spec caliper hanger for the 'F2 dual-disc fork (& subsequent DOHC-4 versions of which) not to mention a new center-carrier & caliper-hanger to adapt the 260mm 6-rivet front rotor from CB350F & CB400F onto the 6-bolt & maybe even 5-bolt rear disc hubs - maybe even a 10-bolt pattern to suit 5-bolt AND 6-bolt rear hubs? Paired up with a caliper-hanger to suit, made so as to KEEP the original single-puck calipers (or an exchange-basis modification of the earlier opposed-pair twin-piston rear calipers, the axle hole welded shut & re-drilled etc etc) All of which would be intended for a complete OEM look on a far far better all 'round brake package.
Maybe a new top half clam-shell case/housing for the throttle side cast alloy handlebar switch housings, with the SPORT-KIT style cable reorientation from the DOHC-4 & CBX550F etc. Simple matter to adapt the Sport-Kit rear-sets peg hangers to the 'F2 maybe even the 'F1 alloy peg brackets - The CB1100R alloy pedal is a nice fit but imho it just plain looks better to cut down the OEM pedal and "telescope" it back together.....
Just sayin' - there are a ton of NON motor related elements of these bikes which could use an upgrade. And when they're done in a STEALTH upgrade, it might just stem the tide of all this STARBUCKS RACER nonsense we've seen these past ten or fifteen years, with the USD forks & 17" cast wheels, the billet shillet bedazzled all over the place, rendered in purple anodize like some sort of radioactive bird poop has landed all over the bike? BLECH. And more to the point - MEH. If we could only make it easier to improve things in the OEM style, maybe people wouldn't just want to throw some random crotch-rocket's complete front end at these bikes?
A bit more expensive, to be sure - but not quite so much if they're whipped up in batch production. And everything to be offered piecemeal, step-by-step. The bigger front discs, the thicker fork, the thicker front axle, the lighter weight yet wider Akront "NERVI" rims for the COMSTAR wheel rebuild, perhaps an exchange-basis service for milling weight out of the rear hubs whether Comstar type OR the wire-spoke - And of course the smaller rear disc center-carrier & matching caliper hanger. A custom FRAME copied from one of the greats, maybe all of 'em? But each one amenable to the OEM bodywork, suspension, running-gear etc? Well mainly the brakes & axles & OEM period-correct (more-or-less fork swaps, etc. The SPORT-KIT stuff in retro-fried SOHC-4 four-mat? Just little KITS is all. One step at a time.
HUGE potential for that kinda thing, imho.
-Sigh.
