Author Topic: Performance of a k1 versus k8 CB750, much difference?  (Read 16999 times)

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Offline 754

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #50 on: February 07, 2009, 06:12:58 PM »
Ok I finally got into part of my stash with 70,s non-chopper mag., I call them the straight Cycle mags. The others are a bit bent!

HTF a roadtest of a sohc 4 on its way out in them days of  dohc 4s.

DID find this FWIW.. Suzi 750 roadtest, clocked a 12.57, which it then stated , 3 tenths quicker than its nearest competitor, the Yam 750... thats was in , I believe Cycle World.

I did have a buddy on a 78F that ran against my 73 off the lights a few times.. lets hear what the 77/78 riders have to say about their runins with the "older 750s".

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My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline BobbyR

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #51 on: February 07, 2009, 06:42:24 PM »
A quote from a 1977 test report:

The K-model is all this plus another 3 percent. It has an edge because it's built and sold as a touring bike, so factors such as ground clearance and weight aren't as significant as they are to a bike with "Super Sport" in its name. Ideally the K model would also have ComStar wheels, dual horns, a rear disc and the F's power, but even without them, it's a fine touring machine tainted only by less than satisfactory suspension compliance. Its 1/4-mile time of 13.33 doesn't seem impressive compared to the F's hot-blooded 12.7, until you realize it's still three tenths quicker than the original CB750, three tenths quicker than the current Yamaha 750, and quicker than the BMW 750. In short it's no slouch, and there's a simple explanation why: the K engine is last year's Super Sport engine with the new accelerator-pump carburetion system.

Because of higher gearing which lets the engine loaf, the K is even smoother than the F2, and therefore a rival to BMW for comfort. Further improvements include new seamless mufflers which look better and quiet the engine's 57.13 horsepowerto 78 dB(A) - a whisper. Redesigned triple-clamp bosses bring the new handlebar closer to the rider, partially to compensate for an inch-longer wheelbase. These changes, along with the new grips and two-stage seat, produce an exceptionally natural feel. It's likely a rider will remain comfortable for a whole tank of gas, which is now five full gallons - enough for 200 miles at a 40 mpg average. Nearly an inch more rear shock travel also contributes to the K's comfort and load-carrying ability. In addition, Honda has fitted the same fat rear weenie that works so well on the heavier GL1000 and Automatic.

Full report here:

http://www.triumf.ca/people/baartman/bike/cb750-77.html
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Offline seaweb11

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #52 on: February 07, 2009, 06:52:44 PM »
My apologies if I offended with my last comment.

It came from 3 years or so on here and the constant "I don't get it" K8 bashing. That is what I was referring to.

Many posts have been tech in content, fine, but the other stuff?
I just don't get it.  I also have more than one 750 vintage bike, they are both cool 8)

I need food.....by now. ;D

Offline Really?

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #53 on: February 07, 2009, 07:08:11 PM »
No offense here.  I would like my next SOHC to be a K8.  I am trying to figure what the bashing is all about.

With all the K8 bashing, why are there so many wanting that swingarm?????
I don't have a motorcycle, sold it ('85 Yamaha Venture Royale).  Haven't had a CB750 for over 40 years.

The Wife's Bike - 750K5
The Kid's Bike - 750K3

Offline moham

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #54 on: February 07, 2009, 07:40:52 PM »
I know there was mention in an earlier post about dyno testing, which leads me to my question: can anyone post recent, reliable dyno tests of straight stock K8, K0-1, F2? Would this side by side comparison of concrete data at least get us close to drawing some sort of reasonable conclusion? I guess if we can't get that there's only one thing left to do: get the rulers out...   
78 750K-The Ocho
74 550-The Cherry Picker
70 750K0 motor-Dick in a Box

Offline bwaller

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #55 on: February 08, 2009, 04:54:52 AM »
I know there was mention in an earlier post about dyno testing, which leads me to my question: can anyone post recent, reliable dyno tests of straight stock K8, K0-1, F2? Would this side by side comparison of concrete data at least get us close to drawing some sort of reasonable conclusion? I guess if we can't get that there's only one thing left to do: get the rulers out...  


 ;D There you go.

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #56 on: February 08, 2009, 08:17:59 AM »
Well as the only racing around here is dirt track, I am not even sure if there IS a dyno here. The nearest drag strip is over 100 miles away, not far but as I have never visited it before, my numbers would probably not be good on any bike.

So I would have to say someone else would probably get a more accurate run on any of the bikes. The upper midwest does not have the racing facilities a lot of the rest of the country has.

Offline 1080

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #57 on: February 08, 2009, 08:46:46 AM »
I know that my 72 with a 73 engine with Hooker cross over pipes was faster that my 78k with Alphabet header in are local 1/8 mile track.

The 78's just weight more.

Back in 1979 my brother bought a  used 77 Kawasaki 650 it was faster that my 78k.

I still love my 78.

Offline Gordon

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #58 on: February 08, 2009, 09:02:15 AM »
Whatever difference in performance there may be between the K1 and K8 can easily be overcome by a skilled, experienced rider. 

Offline cafe750

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #59 on: February 08, 2009, 09:10:03 AM »
There are so many operating variables in flogging bikes at the strip, or even on the dyno, on dynos, even strap tension holding you to the rollers can get you different numbers....it all comes down to ride what you enjoy, and what makes you smile....
"It's an old motorcycle, the wind is supposed to blow your head around, it's supposed to leak oil, the brakes should suck, and every now and then, it should scare you so bad you piss your pants."



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Offline Kev Nemo

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #60 on: February 08, 2009, 09:17:15 AM »
I know that my 72 with a 73 engine with Hooker cross over pipes was faster that my 78k with Alphabet header in are local 1/8 mile track.

The 78's just weight more.

Back in 1979 my brother bought a  used 77 Kawasaki 650 it was faster that my 78k.

I still love my 78.

Where do you think the additional weight comes in? I'm in the process of stripping mine down and was wondering about weight differences..
Destroyed by Design since 2009 http://fallingapartart.com/

- '78 CB750k bobtrack

Offline 754

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #61 on: February 08, 2009, 09:27:41 AM »
Pipes, Seat, Tank, Sprockets, Chain, Sprocket carrier, to mention a few..
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline 754

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #62 on: February 08, 2009, 09:30:43 AM »
Without a dragstrip or dyno..

 Just run 2 bikes against each other, then switch riders & repeat..
Maker of the WELDLESS 750 Frame Kit
dodogas99@gmail.com
Kelowna B.C.       Canada

My next bike will be a ..ANFOB.....

It's All part of the ADVENTURE...

73 836cc.. Green, had it for 3 decades!!
Lost quite a few CB 750's along the way

Offline moham

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #63 on: February 08, 2009, 10:13:35 AM »
There are so many operating variables in flogging bikes at the strip, or even on the dyno, on dynos, even strap tension holding you to the rollers can get you different numbers....
Drag, ok, plenty of variables there, I'll grant you that. But the variables on a dyno have to be negligible, right? I mean, if not dyno then what? What's the standard for performance measurement?
78 750K-The Ocho
74 550-The Cherry Picker
70 750K0 motor-Dick in a Box

Offline Kev Nemo

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #64 on: February 08, 2009, 11:09:51 AM »
Pipes, Seat, Tank, Sprockets, Chain, Sprocket carrier, to mention a few..

ah-I' guessing most aftermarket pieces would cut that down significantly. Motor and frame would weigh about the same though, correct?
Destroyed by Design since 2009 http://fallingapartart.com/

- '78 CB750k bobtrack

Offline Jerry Rxman Griffin aka MuthaF'er

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #65 on: February 08, 2009, 11:50:50 AM »
The one thing we can all do is enjoy discussing this subject.

The one thing we can not do is put new, properly tuned, unadulterated K1 and K8's on the strip beside each other. The only true way to tell.
As of today 3/13/2012 my original owner 75 CB750F has made it through 3 wives, er EX-wives. Free at last.  ;-)

Offline moham

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #66 on: February 08, 2009, 02:48:26 PM »
The one thing we can all do is enjoy discussing this subject.

The one thing we can not do is put new, properly tuned, unadulterated K1 and K8's on the strip beside each other. The only true way to tell.

Ahaaa, new, I guess not. But races between a couple of stock Ks of varying years? Now that sounds like one hell of a SOHC4 Owners Club Event to me...that and a picnic lunch. (Do you think we could get the Boss to play a set or two?) I'm totally there...
78 750K-The Ocho
74 550-The Cherry Picker
70 750K0 motor-Dick in a Box

Offline Hockers Choppers

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #67 on: February 08, 2009, 03:03:22 PM »


Well MY 71k will be faster because it has a 78k rear swingarm and wheel, plus a 120/70/17 tire! AND a 17t front sprocket!! AND a 4-1, AND pods!!! w/125 jets. and center stand removed :o and its painted black ( the fastest color! ) with DRAG bars! and a cafe seat!!!
Take that K8ers!!! ;D ;D ;D
Hope Terry is not on fire!! :'(
The thing about common sense is that, it's not that common.

1978 CB750F SUPERSPORT 850cc, cam, porting, dyna ign, cr29's lotsa elbow grease and $$'s. Worth ever penny!!  (S0ld)

05 VTX1800F darkside
cb750 k1

Offline cafe750

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #68 on: February 08, 2009, 03:48:39 PM »
Well, I hate to break it to ya, but I've got stainless muffler bearings, and synthetic blinker fluid. Hockers, you don't stand a chance....
Now if I could get my flux capacitor working, my F1 would be unstoppable....
"It's an old motorcycle, the wind is supposed to blow your head around, it's supposed to leak oil, the brakes should suck, and every now and then, it should scare you so bad you piss your pants."



Roy, Washington

Offline Hockers Choppers

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #69 on: February 08, 2009, 03:55:31 PM »
OH, You have an F model, that not even fair!! They are WAY FASTER!!!!
The thing about common sense is that, it's not that common.

1978 CB750F SUPERSPORT 850cc, cam, porting, dyna ign, cr29's lotsa elbow grease and $$'s. Worth ever penny!!  (S0ld)

05 VTX1800F darkside
cb750 k1

Offline moham

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #70 on: February 08, 2009, 06:41:14 PM »
and synthetic blinker fluid

I can't believe you use synthetic...
78 750K-The Ocho
74 550-The Cherry Picker
70 750K0 motor-Dick in a Box

Offline Gordon

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #71 on: February 08, 2009, 06:58:58 PM »
and synthetic blinker fluid

I can't believe you use synthetic...


Dude, you can't use synthetic blinker fluid in these old bikes with a wet relay set-up.  It'll cause the switch to slip, not to mention causing the bulb seals to leak. ::) ::)

Offline cafe750

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #72 on: February 08, 2009, 07:33:49 PM »
But the bottle told me it was worth 5 hp...or maybe it just said to slap the sticker on...I remember now, the fluid doesn't work unless the sticker is applied.... ;)

I'm also thinking that I need larger piston return springs...
"It's an old motorcycle, the wind is supposed to blow your head around, it's supposed to leak oil, the brakes should suck, and every now and then, it should scare you so bad you piss your pants."



Roy, Washington

Offline BeSeeingYou

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #73 on: February 08, 2009, 07:49:24 PM »

 and its painted black ( the fastest color! )

This just made me laugh ;D ;D ;D

Offline mick750F

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Re: Performance of a k1 versus k8 CB750, much difference?
« Reply #74 on: February 08, 2009, 07:52:26 PM »
  Hah! I will kick all of your arses with my not completely stock F3. It is by far the most advanced not completely stock once original F that any of you K riders will ever see. I've upgraded and downgraded just about everything you could imagine on this bike and still I could make it faster if I chose to. But I feel that it's important to not outdistance the flock too much if you know what I mean. Damn!! Now that I've mentioned flock Terry is bound to chime in on this worthy discussion. Anywho...come one come all, bring it on. Dragstrip...Dyno...Track. None of you got nuthin' on me 'cause I swapped out the summer air in my tires for winter air and here in the northeast we got the best winter air.  Oh yeah! I'm cold air fast now!!! ;D ;D ;D ;D ;D ;D

Mike
'
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