Author Topic: Top speed for the Honda 750 K's ????????? (Read 10797 times)

sbc1320 · « **on:** January 05, 2008, 05:52:37 PM »

About 30 years back I had my first 750 K (1974) and I remember topping it out at 137 mph. I could get 90 out of second gear if memory serves me right. Just wondering what kind of top speeds for the old stock 750's? Anyone here from Houston, Texas area like me.

merc2dogs · « **Reply #1 on:** January 05, 2008, 06:55:27 PM »

On my old bikes I've hit 130+ a couple times, lately I haven't done much over 90, but that's more a sign of me just not being in as big a hurry to get accross town as I used to be. Used to be a question of how fast you could get from a to b, now I'm more concerned with what I can see on the way.

I've heard people claiming over 140, and others who've claimed (and were willing to argue) that a 750 was simply incapable of anything much over 100 without serious mods.

Ken.

sbc1320 · « **Reply #2 on:** January 05, 2008, 07:00:43 PM »

That's the way I am these day also. Not in quiet as much of a hurry and a little wiser I would like to think. Learned a lot from those days. I know for a fact that my old 74 ran that speed of 137 and I am pretty positive it was stock from original owner. Kinda of respecting this one a little more and hadn't gotten my lately acquired 76 model over 80-90 mph.

736cc · « **Reply #3 on:** January 05, 2008, 07:32:52 PM »

K6 maybe 110mph on a good day and a tailwind
K2 a little more if theres enuff room
K1 will hit 120
K0 as well

One particularly fast sandcast hit over 125mph laying on the tank
836 kitted and worked motors go 130mph+

All the new bikes spank CB750's on top end.

Good thing I don't own a Hayabusa; I like to twist my bikes for all they're worth every day I ride 'em.

PxTx · « **Reply #4 on:** January 05, 2008, 07:37:32 PM »

The older I get...the faster I was!

I know there was different gearing as these bikes progressed. I beleive the earlier ones ran a larger front sproket. I'd guess your speedo could read 137, but I would be skepticle is the bike was actually traveling at that rate. Obviously front tire size could affect this. I've had a few indicate 120 and 125, but it really climbs slowly.

azuredesign · « **Reply #5 on:** January 05, 2008, 07:57:56 PM »

Quote from: 736cc on January 05, 2008, 07:32:52 PM

K6 maybe 110mph on a good day and a tailwind
K2 a little more if theres enuff room
K1 will hit 120
K0 as well

One particularly fast sandcast hit over 125mph laying on the tank
836 kitted and worked motors go 130mph+

All the new bikes spank CB750's on top end.

Good thing I don't own a Hayabusa; I like to twist my bikes for all they're worth every day I ride 'em.

And it's only a quarter of a turn to full throttle on the Busa!

HondaMan · « **Reply #6 on:** January 05, 2008, 08:42:46 PM »

Quote from: sbc1320 on January 05, 2008, 05:52:37 PM

About 30 years back I had my first 750 K (1974) and I remember topping it out at 137 mph. I could get 90 out of second gear if memory serves me right. Just wondering what kind of top speeds for the old stock 750's? Anyone here from Houston, Texas area like me.

Pretty close: my K1 and K2 both reached over 130 when young, but had to have 17/48 gearing to get there (stock K1 was 17/48, K2-later were all 18/48, too tall). My good friend's K0 sandcast toured regularly all day long at 125 with a Vetter Phantom full fairing, not an especially aerodynamic design. His gearing was 16/45, the original 750 sprockets.

Terry in Australia · « **Reply #7 on:** January 05, 2008, 08:58:55 PM »

I don't think any CB750 was capable of that kind of speed "out of the box", but I'd be willing to accept that a well tuned bike with a few sensible mods in perfect weather conditions could come close.

All the test reports of the day were done on mostly new bikes that hadn't loosened up, and I've ridden a couple of "stock" bikes that felt like they had a bit more BHP than others I rode too. As they say in "Myth-Busters", "Plausible". Cheers, Terry.

Blueridgerunner · « **Reply #8 on:** January 06, 2008, 03:15:21 AM »

Saw a Hayabusa on eBay (330201391480) with a stage 1 turbo and nitrous 375HP. So, if you are rich enough & nuts enough, there ya go.

I'll stick with my old, but still good looking CB650 just like me lol

Kevin400F · « **Reply #9 on:** January 06, 2008, 05:16:01 AM »

To your second question in the initial post.....I'm another Houston area SOHC rider/collector.

sbc1320 · « **Reply #10 on:** January 06, 2008, 09:18:24 AM »

I am just outside of the Kemah/Seabrook area. I am not 100 percent sure that my old 74 750 was stock. I just assumed it was, but it may have had some sprocket changes. It did have a 4-1 header on it. I do believe the speedo was accurate and am 1000 percent sure of the 137 mph as I was on the bike. 100 mph is nothing for these bikes. I would try this one out (my 76) but I am just trying to keep a lot more respect for it then I did back in the old days. I would run them hard back in the day never looking at the tach, just listening to the exhaust and as long as it was pulling I had the hammer down. Been around them and riding before I could hold them up. Anyone that thinks these things will only do 100 mph is crazy.

Kevin400F · « **Reply #11 on:** January 06, 2008, 10:21:31 AM »

Hey SBC.... I have an original sales brochure here in Friendswood for the '76 CB750K and CB550K. If you want, I could make you a nice color copy for reference as to the factory original configuration.

Kevin

754 · « **Reply #12 on:** January 06, 2008, 10:23:12 AM »

Around a hundred for a lot of them that arent running crisp. I doubt that you got over 125 with a 74 with just a pipe.. did it have coil, aircleaners, etc?

I knew a guy with a Rickman Kaw that was always talking about doing 140-145!

Then we went for a ride, I asked him how fast we were going. He said 125 mph.. I said my bike wont go that fast!.. then I told him my speedo was only reading a105 or 110..(73 750).

did you buy your speedo off him maybe??..his name was John H..

sbc1320 · « **Reply #13 on:** January 06, 2008, 11:04:29 AM »

No I didn't buy his speedo, but close as my name is Johnny (lol). I don't know if it had aftermarket coils, but it did have the stock airbox on it. That was about 1976-77 and the bike would have only been 3 years old tops. I really don't know for sure, but I didn't think the motor had been gone through. If I ever see the previous owner I will try and remember to ask him. I grew up here and some of my old buddies are still around. I know these old bikes are not as fast as the modern crotch rockets. I also used to have an old 76 KZ900 and those bikes were fast. Thanks Kevin I appreciate the offer, but too much trouble.

HondaMan · « **Reply #14 on:** January 06, 2008, 11:41:35 AM »

When I was doing all that "racing tunig", as they called it back then, one of the most important things to do to the 750 was fresh electrical parts (points, condensors) and lower gearing. I also usually added a bit of extra clearance to the valve lash, new chain and good sprockets (Honda's own), good tires and a bit of tweaking with the spark curve, all as the standard "hi perf" tuneup. I don't ever remember a basically stock 750 that I tuned with this "package" that would not do at least 125 MPH indicated on the 4-mile stretch from the shop to Colchester afterward.

sbc1320 · « **Reply #15 on:** January 06, 2008, 12:07:08 PM »

Only thing HondaMan if you add too much clearance then you are taking away cam lift. Good way to see if the motor needs more or less cam. I am mechanic by trade and have also been building muscle cars for 25 years or so. Sold my last one about 2 years back. It was my daily and only driver, a 1971 Chevy Nova. I built a 406 sbc (all Eagle forged) with AFR 210 heads, turbo 350 (3500 stall), 3:73 rear and posi. Bolt the tires on and drive to the track and runs some 11.60's all day long. Foot brake and leave at idle (nail it) and it would do 1.64 - 60' time. Not bad for a street car all motor. For sure there is always something faster out there though.

merc2dogs · « **Reply #16 on:** January 06, 2008, 12:20:11 PM »

I think a lot of it has to do with the rider, not in the sense of who's the better rider, but instead with the size/weight of the rider.
My buddy Charlie and I get comparable speed/performance out of the same bikes, but Matt is consistantly slower on any bike, Charlie's slightly taller and maybe 15lbs heavier than me,(I'm 5'6" 145lbs, and LOOK 20lbs lighter) Matt on the other hand is a foot taller, and 80lbs heavier. More weight and bulk=more power needed to move at the same speed, the extra bulk means a bit more air drag.

By way of example, my old ranger longbed 4x4 with a 2.3 4 popper with the tail gate up would cruise comfortably at 65mph, with the tailgate down and windows up the comfortable cruise moved up to 75.

ken.

sparty · « **Reply #17 on:** January 06, 2008, 12:40:03 PM »

I am sure Mike Rieck's Million Dollar CB will have a very nice top end speed.

Sparty

Patrick · « **Reply #18 on:** January 06, 2008, 02:14:15 PM »

The only way my bikes would do 120+ is if someone dropped them out of an airplane. I don't know if they're capable. I just know it's not going to happen....

Terry in Australia · « **Reply #19 on:** January 06, 2008, 02:25:11 PM »

Quote from: sparty on January 06, 2008, 12:40:03 PM

I am sure Mike Rieck's Million Dollar CB will have a very nice top end speed.

Sparty

What about yours Art? I think you're being a tad "coy"? I reckon mine's good for maybe 150 now? Might even get a bit more with the APE crank, and if I can lost 50 pounds this year, look out!

markb · « **Reply #20 on:** January 06, 2008, 02:56:11 PM »

I still remember the first (and only) time I topped out my K0. I bought it in '75 and wanted to see what it would do. Completely stock. Kept it at 120 for a couple of minutes. Felt like 150. I still remember the sound! I still have it and hope to have it running this spring after a 2 1/2 year resto.
Mark

Bob Wessner · « **Reply #21 on:** January 06, 2008, 02:57:37 PM »

Look forward to seeing pics.

HondaMan · « **Reply #22 on:** January 06, 2008, 05:06:59 PM »

Quote from: sbc1320 on January 06, 2008, 12:07:08 PM

Only thing HondaMan if you add too much clearance then you are taking away cam lift. Good way to see if the motor needs more or less cam. I am mechanic by trade and have also been building muscle cars for 25 years or so. Sold my last one about 2 years back. It was my daily and only driver, a 1971 Chevy Nova. I built a 406 sbc (all Eagle forged) with AFR 210 heads, turbo 350 (3500 stall), 3:73 rear and posi. Bolt the tires on and drive to the track and runs some 11.60's all day long. Foot brake and leave at idle (nail it) and it would do 1.64 - 60' time. Not bad for a street car all motor. For sure there is always something faster out there though.

Opening valve clearances DOES reduce cam lift! But, in the case of this engine, you can lose .005" of lift and not lose any significant flow, due to the stock intake castings. What you gain, instead, is slightly higher compression, less valve sealing variability, and cooler valves. It always worked when we roadraced them, so I'm sure it still works today.

Then again, if you send the head to MRieck first, add some more degrees of dwell to your cam, raise the CR by other means, etc., the story could change.

sparty · « **Reply #23 on:** January 06, 2008, 05:50:03 PM »

Quote from: Terry in Australia on January 06, 2008, 02:25:11 PM

Quote from: sparty on January 06, 2008, 12:40:03 PM
I am sure Mike Rieck's Million Dollar CB will have a very nice top end speed.

Sparty

What about yours Art? I think you're being a tad "coy"? I reckon mine's good for maybe 150 now? Might even get a bit more with the APE crank, and if I can lost 50 pounds this year, look out!

Oh, my engine is pussycat. It will hit a little over a ton, that is about it...

Terry in Australia · « **Reply #24 on:** January 07, 2008, 02:15:22 PM »

Yeah, but what happens when you change up into 3rd gear?

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Author Topic: Top speed for the Honda 750 K's ????????? (Read 10797 times)

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