Don Vancek's Dyno Test Report

[YellowJacket!]

Note that the guy had his coil pickup wrong so you need to double the rpms.  A ninja 250 just before me did 27 HP but I didn't get the torque on it. The dyno operator said his 82 kz750 Twin (not four) did a about the same HP but 15 lbs LESS torque, interesting!  This was at an open house where if you purchased $25.00 or more you run on this small portable dyno. I purchased one of those little volt meters with time and temperature.

Since the document was  pdf (adobe reader) I posted a link to my public folder on sky drive.  Click the link and it will take you to the file to downolad and view.

http://cid-fbf69431aae6cb93.skydrive.live.com/self.aspx/.Public/File0001.pdf


David  via Don

[Night Vision]

I'm surprised the torque was that much since the claimed is only 37 @8500rpm

guess you got a little torque monster there Don  :)

[Kid Jedi]

oh god, look at the lumps on the torque curve! the stock vision carbs, SOOO BAD!

[Rick G]

The kZ750 twin has a reputation of being a turd, so I;m not surprised.

4 valve engines like the vision, usually produce good torque .

[jasonm.]

Oh I see....now. Only 43hp. ???

Hum, I also had about that on my '82. But my '83 had almost 55hp at it's lest test. I should test my '83 again since I have messed with it quite a bit .  I believe I increased my torque but lowered my peak hp. to maybe 50.

[don_vanecek]

Take this dyno with a grain of salt, it was portable unit and they only did one run (well what do you expect for free). I can see from the torque figure why you hardly ever have to shift these bikes out on the road. As for the KZ750, I asked the operator for somethinkg to compare to and since he apparently has one he know the figures for that, wish I had asked him for some other figures. yes, the torque figure is confusing as specifications do only give 37 ft lbs, I wonder if there is some difference in the math or standards, I'm not surprized on the HP as this was a rear wheel, on the bike pull, I would think the published 65 HP figure is just off the crank. In watching my bike on the dyno I can see I need to balance my rear tire and I'll bet I'm running a bit rich.

I'm kind of glad they didn't try to do another run or two as I think even that one run took a few hundred miles off my rear tire!

Thank you yellow jacket for helping to post this!

[Kid Jedi]

The kZ750 twin has a reputation of being a turd, so I;m not surprised.

4 valve engines like the vision, usually produce good torque .

??? I thought torque was a factor of the bore and stroke and a better valve train affects top end breathe ability / HP ???

[inanecathode]

The kZ750 twin has a reputation of being a turd, so I;m not surprised.

4 valve engines like the vision, usually produce good torque .

??? I thought torque was a factor of the bore and stroke and a better valve train affects top end breathe ability / HP ???

Yes and no. Better, faster, and more efficient valve closing equates to higher and quicker combustion pressure. More pressure = more torque. Hence partially why diesels can pull stumps.

[Kid Jedi]

think the v could run 12.0 to 1 with out cam modification? I think she can....

[QBS]

Do you have a secret source of HiComp pistons?

[Kid Jedi]

Yup. The pistion company owes me a favor (Sold em 2 square feet of tantalum for 500 bucks, loooong story) , They said they would be willing to make pistons for my V, normally they only make em in sets of at least 8 and i don't wanna try to buy in with 3 other visionarys...

Besides, the pistons & rods in the v are VERY OLD tech compared to what is available now. a lot of advancement in steel/ aluminum manufacturing has come out in the last 10 years.

[Ron_McCoy]

Don, Do you still have the restrictors in your carburetors?

[Rick G]

I be happy with  a set of  1st or 2nd over pistons and rings, in the stock compression ratio.

Using a long stroke small bore engine is an old idea to get torque , Big bore short stroke ,with lots of valve area  in a 4 valve configuration is far superior.

[QBS]

If you have custom sources,  go for big bore 650cc items.  From what I've read here, from someone that built a hot rod V (name unknown to me now) V cylinders will bore to 650.  Imagine that with 12 to 1.  Better run Premium grade.

[jasonm.]

FYI- the rods and associated bearings in the "V" won't last at 12:1 and 650cc. Just go to 650cc.

[don_vanecek]

Ron, yes I still have the restrictors on my carbs. Maybe in couple of weeks I'll give the bike a good going over and take em off and see how it runs. As far as I know I still have the caps over the mixture screws on my carbs, plus I'll bet the mixture screws are frozen up by now anyway.

You know it gets to a point where the bike starts fine and runs great, do I really want to mess with it?  On the other hand my MPG seems down and perhaps some adjustment and redoing some things is probably a good idea-I've been thinking I must be running rich for the last year or so. I haven't really messed with the V for awhile other then putting the monometer on perhaps about two times each summer (and of course changing oil, plugs).

Tell me your thoughts!

[Kid Jedi]

if it aint broken...

and i think a 50cc/ pistion overbore on the engine would be excessive. after a niskil coating I wouldn't have to worry about new pistions/rings EVER again, provided i change my oil, but i don't think the bottom end can take much more. 58ft lbs o' torque is ALOT for that little tranny. if i went to 12-1 pisitons i could install MUCH lighter ones, possibly 1/2 as heavy, meaning that the rods and bearings would be doing less work. to offset the extra work of 12-1

[Night Vision]

Don, Do you still have the restrictors in your carburetors?

good point! the way they restrict the hp in Europe for beginner riders is a restrictor plate kit...

Tell me your thoughts!

life is too short... crack open them carbs this winter!

my brother doesn't have a vac flapper so don't let that worry you.
2 nickels on the flapper and he gets over 50mpg consistantly and it's not on flatlands either.

[don_vanecek]

I'll get some new plugs next chance I get and do some experimentation. By the way my flappper door is long gone, I can see where the rivets are, but I don't remember even having one (and I'm the original owner). 

Well we will see what happens! 

[h2olawyer]

Don -

Air box tops are pretty common.  I have an original non-vacuum type.  If you want it, a donation to the ROV site will get it to you.

H₂O