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R/R = Relocated Redneck
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Discussion Starter #1
Good afternoon y'all, one of the local dealerships had a deal last weekend where dynojet had one of their trucks on site. Just for giggles (and the other stuff...) I decided to let them twist mine up to see what the real hp and torque numbers were. My question is more for the folks who have other bikes. I've seen multiple sites where the hp number was around 60 and the torque was somewhere around 47. I didn't believe the numbers represented rear wheel power when I read them and the dyno confirmed it. Have y'all experienced similar findings with other bikes?

 

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1986 VN750
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Clean numbers there.

Most of the time advertised hp/torque is measured at the flywheel, thus a good 10% higher than reality.
 

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Yes most factories report horsepower at the crank, while magazines like Cycle World dyno their test bikes and give rear wheel figures.

"Reported" horsepower for the Vulcan is 63 I believe. I think a member had his earshaved VN dyno'd and reported 53-54 HP.

My FJR listed a HP of 145, dyno runs by owners are in the 125-129 range.

Shaft drive bikes eat up a bit more power than chain drive bikes BTW.
 

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87 VN750 Lookin Good
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Yes most factories report horsepower at the crank, while magazines like Cycle World dyno their test bikes and give rear wheel figures.

"Reported" horsepower for the Vulcan is 63 I believe. I think a member had his earshaved VN dyno'd and reported 53-54 HP.

My FJR listed a HP of 145, dyno runs by owners are in the 125-129 range.

Shaft drive bikes eat up a bit more power than chain drive bikes BTW.
I think you are right knifemaker, my 750 had a little power loss up in the mountains loaded down with 60 lbs of camping gear last summer.
 

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87 VN750 Lookin Good
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I think you are right knifemaker, my 750 had a little power loss up in the mountains loaded down with 60 lbs of camping gear last summer.
Sure is nice to have the "Connie" now. I may take a trip this coming summer, sure is nice to have a 7.5 gallon tank and a thousand cc's.
 

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Sure is nice to have the "Connie" now. I may take a trip this coming summer, sure is nice to have a 7.5 gallon tank and a thousand cc's.
Well as most builders will tell you, if you're looking for more power,


There's no replacement for displacement........;)

My personal view is 900-1000cc is all a bike really needs.
 

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R/R = Relocated Redneck
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Discussion Starter #7
I was pretty happy with the numbers, I actually expected them too be lower because of drivetrain losses. Mine is earshaved and mildly jetted, so that seems like a consistent hp number.
I'm not as concerned with the HP number as the torque number. Add a hill and/or extra weight and she does tend to bog down.

Any feedback on what value there is in adding torque cones to the exhaust?

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Bog down? How big are you? My Vulcan with passenger and 60 lbs of luggage went up hills with no problem. Perhaps your jetting is a bit off, or you forgot you can downshift....;)

Not sure what "torque cones" are but sounds like they just constrict the exhaust...the bike as stock has a well tuned exhaust. Guessing torwue cones are for folks that run straight pipes....
 

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1986 VN750
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I did that 600mi trip with full luggage and my 250ish pound self, and had no issues. I always just downshift on hills and keep the RPMs over 4k. It is a Japanese engine so it's not afraid of mid-to-high RPMs :)
 

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I did that 600mi trip with full luggage and my 250ish pound self, and had no issues. I always just downshift on hills and keep the RPMs over 4k. It is a Japanese engine so it's not afraid of mid-to-high RPMs :)
BINGO!!! been saying that for a while now....lol

i think people are afraid to push the RPM on the VN750, but i swear this bike LOVES screaming above 4K RPM :motorcycl
 

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..have a vulcan good day!
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BINGO!!! been saying that for a while now....lol

i think people are afraid to push the RPM on the VN750, but i swear this bike LOVES screaming above 4K RPM :motorcycl
PowerBand = 3-6 K rpm.
When running in gear, my tach never see's less than 3K rpm.

:smiley_th
 

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It just sounds like it's revving high above 5k compared to other cruisers I guess. But I have to agree that it runs there very comfortably. It's really not fair to compare it to other "cruisers" I guess. This evening I was coming home from work on I-95 doing 75-80 according to my speedo and around 5000-5200 or so RPMs and it felt really nice...except for the wind buffeting from a lack of windshield.
 

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R/R = Relocated Redneck
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Discussion Starter #13
I think that my main jets are still a little lean. I've also got the snowplow fairing on the front and that adds a little extra resistance. Torque cones add a little backpressure to the exhaust. Hp peaked just before 8k, torque at 6k. The curves are a little interesting.


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FREEBIRDS MC CENTRAL NY
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BINGO!!! been saying that for a while now....lol

i think people are afraid to push the RPM on the VN750, but i swear this bike LOVES screaming above 4K RPM :motorcycl
Yes me too.i take mine to redline often and she loves it.
 

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Every bike seems to have a "happy place" where the motor just seems to feel the best. Every bike is different. With the Vulcan, it always felt like it was right between 5200-5500rpms.
From the graph, this looks to be right where the torque begins to peak. Kinda makes sense. :)
 

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I think that my main jets are still a little lean.
How would you know? I think guess is the right way to say it. Although I am not around a wheel dyno much, I know most engines make the most power at the edge of lean. That said, there is little downside to running a hair rich.
Hp peaked just before 8k, torque at 6k. The curves are a little interesting.
Tq and hp peaks appear to occur at a slightly higher rpm than OEM. No way to say if the torque curve is down as would be expected. Cars on a wheel dyno are considered to show 80%. I would guess you bike to be about 65 hp flywheel. Somewhere above respectable.

There is a bike wheel dyno close to me w/wide band sniffer, I thought about using it to adjust just the main jet size. The vn carb jets are too hard to access, and there is always that free air calibration problem.
 

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This is a fabulous thread.

http://s376.photobucket.com/user/me...ter/MotodynoVN800drifter_zps4715d164.jpg.html


58 hp 48 torque that is on a lightly modified VN800 drifter with carb tuning just about as good as it gets according to the dyno operator.

you can see the A/F ratio starts to lean out at high RPM, this is what WM is talking about, and I am pretty sure I am getting the most out of this bike without sacrificing ability to drive it / have a smooth curve.
 

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I wanted to add that if you never brought a bike to redline before, you will be amazed at the power you have in reserve.

kenny
 

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Just to add my thoughts on RPM's. I have always understood that a more critical factor is the piston speed. A short stroke motor will rev higher for a given piston speed than a long stroke motor. 7K revs on my 750 Norton Atlas is close to calamity as it is a long stroke engine, whereas the same piston speed on my ZZR250 is probably over twice the RPM.
The Atlas is safe to about 6K in standard form, The ZZR 250 is redlined at 14K. Not sure about now, but I seem to remember things get a bit chancy with a piston speed of much past 3K feet/min.
 

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Just to add my thoughts on RPM's. I have always understood that a more critical factor is the piston speed. A short stroke motor will rev higher for a given piston speed than a long stroke motor. 7K revs on my 750 Norton Atlas is close to calamity as it is a long stroke engine, whereas the same piston speed on my ZZR250 is probably over twice the RPM.
The Atlas is safe to about 6K in standard form, The ZZR 250 is redlined at 14K. Not sure about now, but I seem to remember things get a bit chancy with a piston speed of much past 3K feet/min.
that is why those inline 4's (street racing bikes) have redlines around 14K, my 800 has a 8K redline.

The bikes today also most if not all have rev limiters.

These jap bikes just love to rev.

I am not sure what you mean by feet / min, if my stroke is 2.6" and the formula for feet / minute is stroke x RPM x 2 then we get 3466 ft / minute if my rpm is 8K

But that is my redline, I mostly run @ 5K when riding aggressive... so

2166 ft / min interesting, don't know if I can do anything with this data, but interesting hehe


kenny
 
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