Topic: Almost Ton Up?

[smccloud]

with a 110 90/19 on the front of my '72, my speedo is dead on.  i've done 100, but i chickened out.  country road in mn, was afraid of a tractor pulling out............

[mlinder]

My speedo sweeps between 100 and 140 at anything greater than 100mph, with, of course, the sweeps becoming more enthusiastic in their velocity as speed increases.
I was clocked at 120 by the speedos of modern bikes.

Damnit, I just said speedo twice, read over what I said, and imagined myself on the beach in a pair of speedos. Not a pretty picture.

[JZEROE]

At low speeds my 550's speedo is dead on according to the radar trailers, but the tach starts getting fresh over about 80. Even though I know it should ~7k rpm in fifth gear (17-tooth front), and it usually starts out correct, but, by the end of a long ride, is reading about 5K. That's some warmup!

But aren't all front-wheel motorcycle speedos inaccurate at high speeds anyway? It's my understanding that, unless the pavement is glass-smooth, the front wheel spends a considerable amount of time skipping undetectably from bump to bump, spinning freely.

[Hope]

I think even a well tuned 550 will do 100+. I don't think I'll try it with all the stories of ancient frame geometry and the evil and hurty tank slap. As long we're tooting our own "horns", my 550 will never do >60 w/my drum kit. 

A well tuned 550 WILL do 100+.     

[Gordon]

But aren't all front-wheel motorcycle speedos inaccurate at high speeds anyway? It's my understanding that, unless the pavement is glass-smooth, the front wheel spends a considerable amount of time skipping undetectably from bump to bump, spinning freely.

Even if that were the case, the wheel would still be spinning at the same speed whether it's in contact with the ground or not. 

[ger87410]

Oddly enough, my wife says my speedo is 100% accurate.  Or there abouts. 

[DJ_AX]

Is it true that the odometer and the speedo are geared together?
And if so than one could easily see the accuracy of there speedometer relative to mile markers.

[TwoTired]

The odometer is mechanically geared to the front wheel.

The Speedometer is magnetically coupled in a bell-within-bell arrangement.  Weak magnets, stiff grease, or friction between the bells alter the needle deflection.

Cheers,

[754]

I guess I should run a speedo, had no instruments when I rode to Bonnevile...

run it at the drags, tour time slip will be accurate to within a few hundredths of a MPH..

No speed errors on the track..



I use Italian intake horns to make mine faster..

[smccloud]

i forgot how scary fast my baby accelerates from 55 to 95 when you need to pass someone and its running properly (i.e. on all 4 all the time).  did it in less than the length of a semi-trailer.

[markjenn]

i forgot how scary fast my baby accelerates from 55 to 95 when you need to pass someone and its running properly (i.e. on all 4 all the time).  did it in less than the length of a semi-trailer.

Ride a GSXR1000, ZX10, R1, or CBR1000 for a few days and the 50-55 RWHP of a good-running CB750 will seem unbelievably anemic.  They have triple the HP and 150-lbs less weight.

- Mark

[ev0lution7]

my old CB750k 77 would do 120 full out and laying on the tank it was pretty quick once you got past the flat spot (air pods and Kerker header) anyways i'm hopeing my new 77 will do the same with stock componets since i've done some upgrades!

[mystic_1]

Ride a GSXR1000, ZX10, R1, or CBR1000 for a few days and the 50-55 RWHP of a good-running CB750 will seem unbelievably anemic.  They have triple the HP and 150-lbs less weight.

- Mark

mystic_1

[gregwaits]

...my new '77 will do the same with stock componets since i've done some upgrades!

I like the way we think! ("new '77"!)

[smccloud]

i forgot how scary fast my baby accelerates from 55 to 95 when you need to pass someone and its running properly (i.e. on all 4 all the time).  did it in less than the length of a semi-trailer.

Ride a GSXR1000, ZX10, R1, or CBR1000 for a few days and the 50-55 RWHP of a good-running CB750 will seem unbelievably anemic.  They have triple the HP and 150-lbs less weight.

- Mark

well, a CB750 running on 3.5 cylinders is anemic compared to one running on 4 cylinders.  not like i would give up my baby for a newer bike though.

[markjenn]

well, a CB750 running on 3.5 cylinders is anemic compared to one running on 4 cylinders.  not like i would give up my baby for a newer bike though.

True, but then again, I'd never give up a current-technology bike to ride only a classic.  While I very much enjoy both my CBX and CB750, neither holds a candle to any current technology bike in almost any area - power, brakes, suspension, etc.  The difference in braking and suspension between my CB750 and even a cheap "beginner bike" (e.g., a SV650) is like night and day.  And a SV650 makes about a third more power.

I'm lucky enough to able to enjoy both old and new.

- Mark

[MCRider]

well, a CB750 running on 3.5 cylinders is anemic compared to one running on 4 cylinders.  not like i would give up my baby for a newer bike though.

True, but then again, I'd never give up a current-technology bike to ride only a classic.  While I very much enjoy both my CBX and CB750, neither holds a candle to any current technology bike in almost any area - power, brakes, suspension, etc.  The difference in braking and suspension between my CB750 and even a cheap "beginner bike" (e.g., a SV650) is like night and day.  And a SV650 makes about a third more power.

I'm lucky enough to able to enjoy both old and new.

- Mark

I too have an FJR, YAHOO!  Only the very best of the current crop can touch it, as you know.

A fully tricked out Dick Mann Daytona replica CR750 is not the equivalent in any performance metric of a current day run of the mill 600cc sportbike. And the price is extremely different.

Good thing playing around with old bikes is just a meaningless pasttime, we can indulge in nostalgia to our heart's content with no real consequence except satisfaction. But we shouldn't fool ourselves. I remember a conversation with a Harley fan who said his boss's stock 70s era Sportster did 130+ with ease. I just smiled and bought him another beer.

But back to the original thread, no reason a stock CB750 with good cylinder compression and good state of tune shouldn't hit 120 with confidence, but that's about all.
Ron

CR750s have been clocked at 150+/- at Daytona, etc.

[DJ_AX]

.....................
Good thing playing around with old bikes is just a meaningless pasttime, we can indulge in nostalgia to our heart's content with no real consequence except satisfaction............

meaningless pastime to some maybe... but it's my primary transportation! 

I've got a car just as a back-up. 

[bhorocks]

well, i hit 105 last night!!  ran the bike hard and it ended up overheating on me... timing or lean i think...

went for a ride with my buddies and they thought it would be fun to haul a$$ on the freeway coming back.  ninja 500  and a kz650.

suprisingly that 92 ninja is fast little bugger.

[markjenn]

But back to the original thread, no reason a stock CB750 with good cylinder compression and good state of tune shouldn't hit 120 with confidence, but that's about all.

True 120 mph with a completely stock 750K bike is pretty tough to achieve.  Aero on a naked bike is, of course, lousy, and to push a naked bike to a true 120 mph takes a solid 60 RWHP, or maybe a little more.  The first 750's supplied to the magazines were near this and with Honda supplying ringer bikes and the journalists crawling under the paint, you could get pretty close, but the later bikes struggled to do much more than 50 RWHP and they're lucky to do much better than 110 mph.

I owned both a 750K2 and a 750F back in the 70's, and the K2 would do about 110 true with everything optimal, the F maybe 5 mph more.

- Mark

[gregwaits]

I bumped 105 last night! 

If anyone else is from here, or is otherwise familiar with Rowlett (TX), you'd know the hiway 66 bridge that crosses over Lake Ray Hubbard into downtown Rockwall. Coming back west from Rockwall with me and my buddy (him riding an '07 Goldwing), I wringed it out and crossed the barrier with about 3/4 mile of bridge left. It is good to back down pretty early because the cops love to clock drivers coming off the bridge.

Now that I've discovered this old girl will do 100, I probably will start to take it a little easier on her!

[gregimotis]

I guess I've done 105 indicated a number of times.  Held 100ish for three hours or so in 90 degree heat to catch up with some friends in southern NM a couple years ago.

It made me tired, didn't seem to bother the bike any.

[fixahonda]

I've hit an indicated 90mph with my 350F. It felt like it still had more left so I'm thinking it should be able to squeeze an added 10mph or so if the situation presents itself.

[MCRider]

But back to the original thread, no reason a stock CB750 with good cylinder compression and good state of tune shouldn't hit 120 with confidence, but that's about all.

True 120 mph with a completely stock 750K bike is pretty tough to achieve.  Aero on a naked bike is, of course, lousy, and to push a naked bike to a true 120 mph takes a solid 60 RWHP, or maybe a little more.  The first 750's supplied to the magazines were near this and with Honda supplying ringer bikes and the journalists crawling under the paint, you could get pretty close, but the later bikes struggled to do much more than 50 RWHP and they're lucky to do much better than 110 mph.

I owned both a 750K2 and a 750F back in the 70's, and the K2 would do about 110 true with everything optimal, the F maybe 5 mph more.

- Mark

I'll accept that. Even I am susceptable to "the older I get, the faster I went"!
Ron

[MCRider]

.....................
Good thing playing around with old bikes is just a meaningless pasttime, we can indulge in nostalgia to our heart's content with no real consequence except satisfaction............

meaningless pastime to some maybe... but it's my primary transportation! 

I've got a car just as a back-up. 

Oops sorry no offense intended. "Meaningless" in the context of things like top speed. Ride on!