100 hp KZ650

very iteresting topic. My recent build consists of 810cc 10.25:1 pistons, gpz head/cams, mildly ported head, no baffele 4/1, pods, 140/70 jets. I sure hope to make around 100hp. In regard to quarter mile times i am hoping for 12's. Does this seem out of line. Yesterday my friends and I ran down the strip numerous times. All the bikes were 750's with pods/header. Every run, except for those with error were in the mid 13's. The fastest pass of the day was 13.4. Although none of us are experienced drag racers whatsoever, this was our first time. We all need ALOT of work on launching, I wasnt using the brake at all and went for the easier roll off the clutch technique. Also, i often had to let off after the front end came up vicuiously because my fork seals are terrible. In perfect conditions, good riders, and with a good launch i dont see why 13's would be out of the question for 650's/750's.

mtkawboy wrote:

I have a jetted & piped 82 GPZ750, so I do share your interest. I have no doubt a built 650 can make 100hp if its an 810.

Yeah, but it's going to take more than an 810 kit to do it

An 810 kit is 807cc (I think), and that's a 69cc increase in displacement. Now, 69cc being just a hair less than 738cc (stock 750 displacement), that's a little less than a 10% increase in displacement, but I'll be generous and call it 10%. A 10% increase in displacement should lead to a 10% increase in torque, and a 10% increase in hp, so that means a 74 hp KZ750E (or a 650 with 750 head/block/cams/carbs) will increase to 81.4 hp, a long way from 100 hp.
Starting with a 83-85 GPz at 85 hp, by adding 10% more you get to 93.5 hp, closer but still not there.

Compression increase will add another 2-3 hp, according to the calculators available on the net, which boosts the KZ750 to (I'll just round off here) 83 hp, and the GPz750 to 95 hp. Getting closer, but still not 100 hp.

Id have to see the numbers on a dyno not a computer to believe a 100hp real 650.

You and me both, but I'll settle for a pic of the dyno printout

Ive had Kawasakis since 73, I know how to fix them and new bikes dont fit old people, If I wanted one Id buy one, but I like the old ones with no water or radiators even if its better.

My first Kawsaki was a 69 A7 Avenger, probably the fastest 350 ever made
I'm not a die hard Kawasaki fan, I've had lots of other bikes, and I like a lot of the new bikes (but I can't see spending the $$$ for new), but through sheer circumstance, most of the bikes I have owned since I returned from the UK in 1975 have been Kawasaki's. There seems to be some kind of mutual attraction force at work.

Im still learning stuff on this forum. My statement did not indicate a dislike for 650s, if it came off that way, I apologize

I don't know about anyone else, but I took it as a "why are you wasting your time and money doing that" thing, so I simply explained my reasons for doing so. I don't expect anyone to think the way I do, and I'm surprised when anyone does

I didn't include the most important (to me) reason, as I doubt it applies to many here.

I'm a nerd/gearhead/dreamer guy that reads "extensively", and I even read things like research papers, Doctoral Thesis, etc, and I have picked up a wealth of ideas on airflow and combustion management techniques over the years. Being your average poor broke individual without access to the big buck projects, I have to try this stuff on my own, and the 650/750 motors are cheap, plentiful, and easy to work on.

I "think" I can get 100 rear wheel hp out of a KZ650/750 motor, using some of the ideas I've picked up over the years, and I'm going to try.

I just have to find out if I'm right, or if I'm full of crap

I believe it can be done as an 810 or larger with a full competition head, cams & big carb & compression. How rideable it would be may be a problem as it will be kind of light in the low end torque dept. I have my doubts that it can be done as a true 650, Id also settle for the dyno sheet, As far as why anyone would want to do it, because they want to and because they can works for me

100 rwhp with a stock 650 bore and stroke?

That's easy, create a new head casting with vertical intake ports and 4 valves per cylinder (titanium valves), custom made cams, all titanium valve gear (buckets/retainers/etc) custom rods that will hand 15k+ rpm, custom lightened pistons, fuel injection with big throttle bodies, and about ten years of development work. Basically recreate a 2008 ZX6/R6/GSX600R motor but in air cooled form, and turn it to 15,000 or so rpm

I think that if you squeezed every dime, you could probably do it for no more than $100,000.00

I'm not going to use carbs, I already have all the EFI stuff, more power and better drivability.

Why didnt I think of that ?????????? :laugh: . Jack up gas cap, drive new 636 or 600 Kaw under, lower gas cap & tighten

mtkawboy wrote:

Why didnt I think of that ?????????? :laugh: . Jack up gas cap, drive new 636 or 600 Kaw under, lower gas cap & tighten

Yep!

But the original post that started this thread specified a 650 with 750 cylinder block bored to 810

And 100 hp at the crank is fairly easy with the specified engine combo.

Here's the homepage of a guy that did some thorough testing of diffrent mods. His bike finally made 93 hp...

There is also a pic of the 1983 superbike that supposedly made 125 hp (This should definately be a 750, superbike rules wouldn't allow bigger bikes!)

He also has a pic of a 'Tsukigi Zephyr' which made 120 hp, and looks killer!!!

That's 93 PS, or 91.7 hp (according to an online converter), and that's at the rear wheel, so somewhere near 113 hp at the crank.

He says something about 2nd gear wheelies, wish my German was better.

Google translation

Looks like the 83-85 GPz750 head combustion chamber as I posted earlier, and it has not been cut for more compression.

A 55% increase in power is nothing to sneeze at!

Just for reference, here's a pic from the combustionchamber of a 2002 Kawaski ZR-7:


It still has the same design as the GPZ heads...

I bought this head a while ago, and I'm planning on doing some mild porting and skimming, and putting it on my KZ700.

Yep, looks just like the 83-85 GPz750 head.

You don't need to do anything to a KZ650 to get 100rwhp, because Kawasaki did it all for you.

It's called the GPz750 turbo, and 100hp is where it starts...

Lorcan wrote:

You don't need to do anything to a KZ650 to get 100rwhp, because Kawasaki did it all for you.

It's called the GPz750 turbo, and 100hp is where it starts...

Yes you do, you have to locate then buy the GPz750 Turbo

Or let your Nephew buy one and park it in your garage (worked for me)