Topic: how quick were the cb750s?

[Stert]

i have not taken delivery of my bike yet....still waiting patiently  =)
but i was wondering how fast these bikes were? mine is a 1974. a couple of my friends either already have some pretty big crotch rockets, or they are looking to buy one.

i did not buy this bike to keep up with their bikes, but i am still curious.

[puppytrax]

There are several Road Tests of the various CB750's right here on this Forum...   

http://www.sohc4.us/index.php?option=com_content&task=category&sectionid=9&id=32&Itemid=89

[Blaize]

Well in a flat out race they are going to just walk away from you, no contest.  But in traffic ie: all riding in a pack, you should be able to keep up withought too much trouble. You will damn sure be working a little harder than they are to go the same speed, but that is sort of the reason these things are so much fun. You can really stretch its legs and not be going "that" fast by modern traffic standards. All depends really on how much they are going to try and prove they are faster. I have ridden with some guys who just sort of feel out a comfortable speed for the pack and do that, and others will haul ass everywhere they go. Of course that type are never much fun to ride with or be around, but all the same it happens.

 Good luck with the new bike, I have owned all sorts and cb750's are really some of the most fun to own. I would be on the edge of my seat waiting if I were you.

[GroovieGhoulie]

I read period road tests.

The K0 would run down to 12.6 or thereabouts, but folks accuse them of being ringers.  The K3, which is similar to yours, ran 13.6 @ 98 mph in a Cycle test in '73.  My 76 F ran 13.1 at 103 mph in a test, and some F1s were reportedly a little faster.

[736cc]

Sandcasts, K0's and K1's will do an honest 120+ mph if you tuck way down. Later K bikes w/ restrictive pipes, airbox and jetting lucky to do 110, they definately run out of steam around 95-100.

[GroovieGhoulie]

The F models did bring back the Sturm und Drang of the early bikes, just not the good looks.  That same road test of my F1 said they could hit 120 at red-zone and 125 if the red zone was entered, but not exceeded, (which the manual says is alright, just not for long periods of time).  As you mentioned, you ARE in a full tuck at those speeds.

The F models, though the styling IS an acquired taste, were faster than the K bikes, (except the K0s and such), all else being equal.

[Snowdigger69]

My 78 750K with Farings, stock 4 in 4 will do 115 easily. My 750K with Kirker 4 in 1 does 110 but you get hammered with the wind. Not bad for a 250# plus rider.

[andy750]

1974 CB750K4 (unfaired, stock jetting, sprockets etc) road tested on the German autobahn, hitting an indicated 105 - 110 mph in top gear and not redlining so could
have gone more Im sure but when you are hitting that speed on a 500lb machine with weak brakes it feels more like a missile that will be hard to stop 
have fun and dont run out of road!
cheers
Andy

[ic455]

Well, IF my speedo and tach are accurate on my 750 K6, I can hit 70 MPH in 2nd gear at right around 7000 RPM.  Then I grab a gear and back off of it so I can try to swallow my jewels back down to their proper place.

[mlinder]

4.5k to 9k on my bike in third is downright scary. Most people street riding won't want that kind of acceleration regardless of the bikes they are on. Also, since our bikes are old, 'fast' feels 'really fast', when in fact, it's only fast.
For freeway riding, a good fairing (bullet shape, not the viper, but the larger, better, more expensive ones) should allow you to keep up with your friends if they are riding at any reasonable street speeds.
I've hit 140+ on a built up 1972 BMW and a classic race fairing. Didn't make much more than 80hp at the rear wheel. Ran out of revs, actually. They were quite low geared.
In any case, being tucked behind a good fairing makes all the difference in the world, for stability, comfort, top speed, and acceleration at the higher speeds.
Remember, Only two things limit your top speed: Horsepower and Resistance. Less resistance, higher top speed.
Acceleration is a function of weight, power and resistance. Having less resistance, after about 50 mph, will greatly reduce your time in acceleration to your top speed. Resistance increases exponentially. Weight limits your acceleration linearly.

So get a good fairing, and get good suspension. Should be fine. If you can't keep up, they are going way too fast.

[HondaMan]

Check out my post in "thoughts of Hondaman" that someone put in there: it covers some of my experiences past with the different generations of the "K" models.

My K2, with Vetter fairing uppers and lowers attached, would run to redline in top gear on 18T/48T gearing, about 132 MPH. With the 17T/48T I have on it right now, would do 126 MPH if I could take the time to synch my $%*&! carbs. Been too busy riding...   
...and, the bottom end has 115,834 miles on it, so I'm not real sure a full-throttle, redline top gear run is advisable just now....but it will do the ton OK, been there...

[CB750R]

dam carbs and jetting wont get me past 140km/h right now!!! no ton up yet for me!!

[seaweb11]

Maybe by next Spring, I'll know what an 836 with fiberglass body will do. Man tha't going to be a great day

[Gordon]

One big factor to consider in all this is "Indicated" versus actual speed.  My 750 speedometer shows about 10% (percent, not mph) faster than I'm actually going, and I've found this to be similar on every bike I've owned and put to the test.  So when it shows I'm at 100mph, I'm really only doing about 90. 

[ic455]

One big factor to consider in all this is "Indicated" versus actual speed.  My 750 speedometer shows about 10% (percent, not mph) faster than I'm actually going, and I've found this to be similar on every bike I've owned and put to the test.  So when it shows I'm at 100mph, I'm really only doing about 90. 

That's something I mean to look into as soon as I can, going to try and have the wife pace me on the 4-lane so I can see where I stand with this speedo

[HondaMan]

One big factor to consider in all this is "Indicated" versus actual speed.  My 750 speedometer shows about 10% (percent, not mph) faster than I'm actually going, and I've found this to be similar on every bike I've owned and put to the test.  So when it shows I'm at 100mph, I'm really only doing about 90. 

In stock trim (3.25 front tire), my K2 would indicate 100 at 97 actual. After installing a K81 (4.10 size tire), it would indicate 100 at 103 actual. Big difference in those tires: the K81 OD is considerably taller with the trigo profile.

[merc2dogs]

 My old 78 had a higher top end than my current 74, I have the 74 geared lower now so a ton is pushing it, but the 78 would it all day long.
 max on the 78 was 120 depending on temps and wind, the 74 will -do- 110, possibly more but it's winding heavy, so that's as far as I've pushed it. Bigger tire/smaller sprocket may it help there.

 It winds up a bit easier, and has more grunt then the 78 did, but I never tried to find top end with the original size sprocket and tire combination on it.

 I always use mile markers to check my speedo, and use the corrected speed

ken.

[Snowdigger69]

I check my speed with a Garmin Legend GPS less error.I have a mount for the handle Bars.

[jonbuoy]

I have been wondering about this too  - A VFR400 makes about 55BHP and weighs 170KG VS CB750's 260 odd kg's.  I think I would struggle to keep up with a CBR250 on a twisty road.  But hey thats not why I bought it.

[HondaMan]

I have been wondering about this too  - A VFR400 makes about 55BHP and weighs 170KG VS CB750's 260 odd kg's.  I think I would struggle to keep up with a CBR250 on a twisty road.  But hey thats not why I bought it.

I learned a valuable lesson about HP and bike riding from Bugsy Mann himself, when he came through our little local racing circuit one day in the early 1970s. He was just passing through with a friend, and went to see a local race. Someone loaned him a street-stock CL350 with those squared-off "street" knobbies and he ran in a qualification heat with our local hotshoes, who mostly rode modified 500/650 Triumphs, 750 Nortons and one 750 Harley.

...and he beat them all by over 100 yards in 10 laps of the 1/2 mile track....and then he complimented the bike's owner on keeping it so nice and well-tuned.....

Moral: don't let 1/4 mile times or raucous acceleration scare you away. I've taken many 850 and 900 BMWs, 1000 Kaws, Suzy 1100s and Yamaha 1100s in the Rockies with my 750. When the road's not straight, it's about HOW to ride....

[Sam Green Racing]

With the old 60bhp motor the CR ran 127mph (electronicaly timed) with 9000rpms showing and on high gearing.

With the new motor, it's running 117mph in 4th gear at the end of the quarter, on lower gearing.

Can't wait to see it on a flyer with the tall gearing.

Sam.

[techy5025]

Didn't Honda get sued for speedo's....and therefore odometers...that registered too high.  Something about the warranty ran out sooner. I haven't checked the 750's, but I know the F4I reads 60 for a true 57 according to the Zumo GPS. Maybe that was their cars they were sued for. 

Jim

[Gordon]

Didn't Honda get sued for speedo's....and therefore odometers...that registered too high. 

The speedometer and odometer are not linked together, so it's very possible for one to be dead on while the other is way off.  My 750 speedo reads about 10% high but the odometer is perfectly accurate. 

[Shenanigans]

apparently some will do "180"


http://cgi.ebay.com/ebaymotors/IT-WILL-DO-180_W0QQitemZ190115754609QQihZ009QQcategoryZ80647QQrdZ1QQcmdZViewItem#ebayphotohosting

[Gordon]

apparently some will do "180"


http://cgi.ebay.com/ebaymotors/IT-WILL-DO-180_W0QQitemZ190115754609QQihZ009QQcategoryZ80647QQrdZ1QQcmdZViewItem#ebayphotohosting

This is a joke, right?

Entire auction description:
"Vehicle Description

   CB750 has bean up grade it will do 180 I like fase bike so needs some crab work.. "