CBR RR throttle bodies

[misterprofessionality]

No point blindly throwing a pile of parts at the bike needlessly.

Until you do the math- the stock tb may be perfectly fine, same goes for the valve sizes, head port flow, etc.

You could easily loose power by making parts too big by loosing velocity, changing pulse resonance, etc.

No way would I ever consider ‘converting’ to another bikes TB. You’ll never get it to work correctly the same as stock.

What I would do- *IF* the tb ever became the bottleneck is start with old hot rod tricks-like permanently securing the butterfly screw threads and then grinding down the screw heads, thin the shafts, possibly remove one side of the shafts.

Heck, if you want to go crazy you can have a machine shop remove the stock plates, bore the housings to a little larger ID, fabricate new larger plates.

That would give you ‘bigger tb’ with no conversion mounting / control hassles.

As already said- there is a lot to do before you get crazy.

Bigger pistons and upping the CR certainly would make power with relatively easy work. Like the cams, you would need to have them custom made.

Would be next on my list if I ever want more after the cams are done. Probably will never do them though as I have never seen an aftermarket piston last like an untouched factory engine- doesn’t matter if on a bike or a car.

Why don’t you start by adding 2-3 teeth to the rear sprocket or dropping the front a tooth?


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just curious a bit....but i'm wondering, why not buy something like a ZRX1200 or the like if you really want a modern inline-4 with that kind of power? is it just about the aesthetics of the CB11?

I own a ZRX1200. Has a full pipe and jet kit. Makes a ton of power compared to the CB.

Yes- I like the CB look and vibe.

If you go on the ZRX forum you will still find guys hot rodding- bigger pistons, bigger carbs, cams, etc.





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I wanna say I do actually totally get it. I'd love to have the knowledge and tools to make my CB have more "go," so I wasn't trying to come off as "go buy a ZRX!" I was genuinely curious what the drive was behind making such an extreme change. Now, the question I'm going to ask is even dumber:

is it cheaper to make a CB11 go as fast as a stock ZRX, or to make a ZRX look like a stock CB11?

Well, it would be impossible to make a ZRX look like a CB, so that's that. The ZRX is still cool looking in it's own sinister way.


A stock ZRX1200 puts down about 115whp.

I don't know how close we will ever come to that unless someone goes completely nuts throwing money and probably long term reliability out the window.

And the ZRX1200 responds VERY nicely to modifications, even on old school carbs. http://www.muzzys.com/ZRX-1200/mods/index.html

Here is the review from the site that made me lust after a ZRX1200 for many many years until I finally bought mine- http://www.motorcycledaily.com/2001/03/2...1zxr1200r/

well, i didn't mean what would it cost to get a ZRX to look *exactly* like a CB. that is, yes, impossible. just as it'd be impossible to get a cb to perform exactly like a zrx. i'm talking about degrees of proximity.

from your response about increasing power, though, it seems quite clear that it would cost a stupid amount of money to get ZRX (or near) power and handling out of a CB, if it's even possible. So, you could conclude that doing a bunch of body work to style a ZRX like a CB is the more efficient route.

ignore me, it's just a dumb thought experiment.

[beardyweirdy@me.com_imp]

It’s worth thinking about weight as well. Add less weight and you’ll get a speed and handling bonus. The Over Ali. Box section swing arm on my bike is 14lbs lighter than stock. You’ll feel that...
But if you do both then it’s smiles all round.
I would say that if you chase the big numbers you’ll possibly sacrifice the bottom end. I had a ZRX and it pulled your arms off when you got the revs up but it didn’t have that low pull my CB has.


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[PowerDubs_imp]

I had a cyl head ported on one of my modern cars- spent a couple thousand all said and done on the project (spare head, shipping, porting, gaskets, etc to install)

The head showed great improvement on the flow bench. Made zero gains on the dyno.

Again- not everything that worked on engines from 30-40 years ago still applies.

Stuff like cams, muffler, fueling- sure because we are removing intentional limitations Honda had with sound, emissions- but stuff like TB and valve sizes, cyl head port shape and casting flash flaws, well I'd really be surprised to see any big gain. But lets see if we can dig up the valve sizes for S&G.

1140cc is a good amount of displacement- agreed.

[Roper_imp]

Has anyone tried to shoehorn a different motor into the CB1100? Would that be easier than all the mod work? I mean, I know that people put a Chevy V8 small block into a Miata. Just wondering if anyone has tried something like that with the CB.

[the Ferret]

Here is something I think about when I think about performace upgrades. Some of the greatest engineers or mechanics or tuners are Japanese. The CB is hugely popular in Japan. The aftermarket for the CB is huge in Japan. If much could be easily gained by massaging this motor as some would have you believe, one would think Samurider would show big bore kits, cams, larger valves etc on his website available for purchase. It was certainly like that with other Japanese bikes the entire time I was in the motorcycle industry from 1972 to 1989. Performance enhancing mods are readily available for other Japanese bikes..ZRX's, Hyabusas, GSXR's and many other bikes that don't really need it, but not being available for one that quite a few people feel could use a boost, and would gladly pay for makes little sense to me. You can buy fairings, and exhaust systems, and swingarms and wheels, and sprockets and body parts galore, any little trinket to make it prettier, or tricker than the next guys, but not one motor part offering to make it faster. Why do you think that is?

Like I said, just something I sometimes think about.

[PowerDubs_imp]

Not a large amount of these bikes exist overall, combined with mostly older tame riders, of which very few people who would tear into their engine, especially given cost.

I don’t think there is any reason beyond that other than nobody has done it yet.

If the cams work, do you really think nobody will follow suit?

And from the tone of your post- you really think Honda engineers got all they could out of the bike?


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[the Ferret]

Not a large amount of these bikes exist overall, combined with mostly older tame riders, of which very few people who would tear into their engine, especially given cost.

I don’t think there is any reason beyond that other than nobody has done it yet.

If the cams work, do you really think nobody will follow suit?

And from the tone of your post- you really think Honda engineers got all they could out of the bike?


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The tone of my post was not one of statement, but one of questioning. I'm certainly in no position to say if or if not Honda got the most out of the motor. I'm no engineer. Just a guy who sits around and ponders the whys and why nots of motorcycling.

Surely in the 8 years this bike has been in production, some professional hot rodder has opened up the motor for a look around to see what can be improved. Yet we have not read of that happening. Only experimentation by owners like beardy and you and the guy from Florida whose name escapes me now who was the first on the board to have the ecu reflashed. Someone help me with the name please. Anyhow..no hop up word by a big go fast motor company out of Japan .. Like Yoshimura. Are they down to just building noise for money? Because their pipes add very little horsepower for the investment.

You say if your cams work, do I really think no one else will follow suit? First I imagine some would. So we are both admitting there is a market for parts to make the bike go faster. If that is true, why is no one jumping in to fill that need? Why can you buy a titanium no cat exhaust for a couple grand for this bike?

Or a swingarm which weighs 14 pounds less than the stocker? Or a set of wheels which drops 7 pounds per wheel for thousands of dollars? You can buy fork kits, rear shocks, handlebars, tanks, seats galore, side covers, emblems, headlights, tail lights, turn signals, etc ...

Yet no one is making a big bore kit or cams. WHY NOT? See I am not stating anything. I am questioning. Pondering if you will.
Motogeezer... It was Motogeezer. Either he was the first to reflash or Cip57. Can't remember now. Both gave up on making the CB faster and moved on. CIp to a Kawasaki 1000 and Geezer to an Apilia iirc.

[jtopiso_imp]

I had a cyl head ported on one of my modern cars- spent a couple thousand all said and done on the project (spare head, shipping, porting, gaskets, etc to install)

The head showed great improvement on the flow bench. Made zero gains on the dyno.

Again- not everything that worked on engines from 30-40 years ago still applies.

Stuff like cams, muffler, fueling- sure because we are removing intentional limitations Honda had with sound, emissions- but stuff like TB and valve sizes, cyl head port shape and casting flash flaws, well I'd really be surprised to see any big gain. But lets see if we can dig up the valve sizes for S&G.

1140cc is a good amount of displacement- agreed.

I agree. The CB is limited due to emissions, consumption, noise, durability... but I am sure it is also as efficient as it can be, so the "volumetric efficiency" must be pretty much optimized from stock: there won't be any signifficant bottleneck on its breathing.

A different thing is that valve timing can be changed to get more power on the high end (at the cost on losing some on the low end, or worsening emissions, or some other regulations the CB must adhere to from stock)

[PowerDubs_imp]

I am unfamiliar with that little bike – is it air cooled? What was its redline, what rpm does it make peak power?

A properly breathing modern engine liquid cooled with a four valve head barring any obvious restrictions should easily make 10 hp per 100cc without having to resort to trade off of high rev horse power losing low RPM torque


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[jtopiso_imp]

the '15 KTM390 Duke (actually 375cc). i traded in for the CB, stock, had 43 rwhp at 1/3rd the displacement. same regulations, if not more. No, the cb is nowhere near 'volumetrically efficient' .

Well, I guess the CB could rev higher, but that's non related to being or not restricted at the TB or intake.