'83 XJ 650 vs. '80 CB 750

Just wondering if I understand this right...

The 650 should blow its doors off, right?

CB750 68 hp (51 kW) @ 9000 RPM, weighs 500 lbs dry.

From http://en.wikipedia.org/wiki/Honda_CB750

Wikipdia says the XJ has 71 hp (51.8 KW) @ 9400 rpm, however, which while still more than the CB, is less than I've heard here. Where is a good list of stats for our bike?

 

Bikez.com

"blow the doors off"? No, they are just about equal in performance.

 

Actually, that was me. I just realized that I goofed and in your other thread I listed the brake horse power for the 650 Turbo.

Totally my mess up. I have too many numbers in my damn head.

Gonna go fix that other one right now.

 

Never seen a CB 750 with doors on, no wonder it's so slow, got any pics? :roll: :roll:
:twisted: :twisted: :twisted:

 

I'm sure if we looked hard enough on the interweb we could find a CB750 with doors, roof, 28" wheels....all kinds of ugly! LMAO

 

Haha. Ok, cool.

On the topic... What would be the proper way to shift, if racing? I have no intentions of doing so, but just for fun threw the throttle all the way back today to remind myself what I'm riding--I realized I wouldn't be sure where the peaks in the powerband on this bike are.

(Assuming a straight line, of course.)

When I say proper way, I mean at what RPM's should I be shifting to get the "mid 12 quarter mile" this bike was known to be capable of?

On the side, a very pretty bike I ran across a moment ago, have to share with someone:
http://sanantonio.craigslist.org/mcy/2954329239.html

 

Max speed and power is made by shifting right at or near max RPM

9,000 RPM, but be warned, by the time you hit 9K in second you will be breaking the speed limit.

 

Everything Takaz said is right, when you want max acceleration, lean forward on the tank to keep the front wheel down and no clutch on upshifts! Sometimes, depending on the bike, I'll start at the max torque of 2nd gear.....on a bike with, say, a 9500 redline, it will be around 7200-7600 rpm. You need to know your engine and how it revs. If you are just beginning to the learn how to get max 1/4's, start out in first gear. You can do it differently later but use first for now. There's no point in running past the point of max acceleration so you need to shift fast. Keep in mind that 3/10th of a second shifting each gear cost you a full second in the quarter mile. At first, practice clutchless upshifts by dipping or chopping the throttle a millisecond before you shift. As you get to know your bike, you'll see how much you can gain by not using the clutch on the upshifts.....and the best part is it won't hurt your tranny a bit!

I used to practice a lot since back in the day, we raced from a standing start. You will be amazed how slow you are at first! I sure was. I remember reading that the bike I was riding was capable of 12.8-13.0 1/4's (a '71 H1 at the time) so on the way to the drag strip I was telling my friends that I figured I'd hit a 13.2 or maybe even a 13.15. I was so embarrassed when my first run, that felt like I nearly had nailed everything, was a woeful 14.7!!!! Yes, you will be THAT slow! After some practice and setting up my bike correctly, I was able to remove almost a full 1.5 seconds off that time though so don't get discouraged. It takes skill and practice to turn your bikes best time but its a big advantage when you "race" someone else who hasn't practice and doesn't have your skills....you'll be able to "beat" much faster bikes because the rider doesn't know how to extract the speed!

jeff

Enjoy

 

Tsakz: 9k for each gear?

What do you mean when you say you 'start' at the max torque of second gear? Do you mean putting the bike in second, revving up to 7200, and taking off there? (I have no idea what that would do, if it would even work).

Why 7200-7600 instead of 9000?

Also, how great is the risk of throwing a rod when doing this?

Do people no longer race from a standing start when doing the quarter mile?

 

I would be most worried about blowing a seal @ redline or close to.

Quarter mile is still done stopped. No rolling starts.

I speak from experience. Neutral drop the clutch at over 5k and your gonna either pop a wheelie or do a burnout. Ive done both, and with shaft drives you tend to burn rubber instead pf wheelie. Just keep your back wheel straight and youll be fine.

-Kaya

 

Kaya, I don't know about the dropping it at 5 grand just causing wheel spin. If you have a real soft compound tire, do a burnout and set up on a good strip of rubber at the track, dropping the clutch will see you on your ass, looking at sky and hearing a very loud "OHHHHHHHHHHHH" from the stands. 8O
I took my Maxim-X down to the local strip a few times and even sitting almost part way up the tank I had a hard time keeping the front wheel down. :x
One of the regulars came up to me in the pits and suggested I slip the clutch during the launch and then upshift without it when going down the track. 8)
My best time ever was a 12.05 at 110 miles per hour.
This was my experience, certain individuals may experience different results! :roll:
^^^ there's always a disclaimer! :twisted: :twisted: :twisted: ^^^

 

Yes, if the mill is healthy you should be able to go to redline without damage. You don't want to hold it there, that's what the shifter is for

Max torque and max bhp are not made at the same rpm. In 99% of engines, max torque is achieved before max hp. Torque is what gets you moving quickly, bhp is what makes you faster in the long run.

Diesel engine: way more torque than bhp, so a semi can pull 40 tons, but can't do 150mph.....at least not without a LOT of modification :twisted: :twisted: :twisted: