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Steele, I was thinking of revs in the 12,000 to 12,500 range because of the larger pistons. I think the crank will hold together. From my research the main bearings used in the KZ650 or developed for it are used in a plethora fo Kasasaki's including all the way up to ZX-12 what do you think would have to be done to the crank to achieve 14,000 rpms. Would I get a full season out of it? I've read on other posts about nitriding the crank. Who would you send to crank too? Everyone is telling me Falicon. They did my Z-1 crank and it has held up. Bruce Sauer built that engine for me and swears by them. I did my KZ650 motor and it has held up even better. All I did to it was open the oil ports up on it. It wasn't balanced or lightened.

Post edited by: ahrma120, at: 2006/01/02 12:27

The rods from a 84 85 GPZ 900 have the same diameter con-rod end as the KZ650/750 bu the larger pin diameter of the kz900/1000. So therefore you can run any piston kit for a 900. I was originally going that way. The rod is larger and heavier and I think would add to crank failure. I am leaning towards custom pistons with stock rods shot peened for strength. Higher R's I think should be my goal. No we are not allowed Turbo's Superchargers or nitrous. Must be stock block and head. We are allowed any modifications.

I have read both and have them saved. The Dave Dal Farra article I found right after I commited to building my Z-1 for AHRMA. That is what got me thinking. My problem is a competitor has got a CBX with 130 at the rear wheel. It wasn't a problem until he got it handling. He move to motor up and angled it down for ground clearance. I don't want to have him walk away from me on a straight. Daytona and Mid-Ohio and Willow being the culprits.

Darlington thank for your input. The chassis I have sorted. This is my third chassis. I'm running a ZR-7 Triple trees with 41mm Concours forks and a ZX-6 wheels, 17 inch. The rear shocks are adjustable ride height 16 inch piggybacks from progressive suspension. The concour forks will have 1.0 kilo springs with emulators if I can't find cartridge inserts, which I haven't been able to yet. The frame is multigusseted which I have been helped out my a wonderful frame engineer from Honda, Ishii Hidefumi. He marked out my Z-1 frame which included replacing main top spar with heavier tubing. Running total loss narrows the motor up quite a bit. The increased height allows for more ground clearance. The 17" rims allow me to run modern compound plus rain tires. The seat height will be about 32" at present with the plastic 82 GPz seat which will have much reduced foam and reworked to fit the KZ750 LTD frame which has the stepped down center section, which I hope will produce a slightly lower center of gravity placing me a couple of inches lower than if a GPZ 750 frame was used.

The GPz900R rods are, I think, 4mm longer. This isn't a bad thing as it improves the rod/stroke ratio which should boost the torque and give less deflection on the crank. You would need a base spacer and slotted cam wheels to reset the cam timing though. One of the guys on my site is doing this mod with his turbo.

You're not going to get 120 hp out of a 650 or even a 750. I doubt you could get 100 hp, and if you could it couldn't take the rigors of racing anyway. Sorry, but you better rethink all this. This is why the factories had to move on from air-cooled to liquid-cooled motors. Even a Zixxer ZX-6R isn't going to make 120 hp.

Just to satisfy my curiousity, what is the advantage of longer rods? The stroke doesn't change if you use different lenth rods on the same crank (right?), so I don't understand the improvement.

You're not going to get 120 hp out of a 650 or even a 750. I doubt you could get 100 hp, and if you could it couldn't take the rigors of racing anyway

You did not qualify your statement in any way, so I just have to point out the link in the post right above yours, "200 hp 750"

Stock 83-85 GPz750 is 85 hp, so you are saying you doubt it's possible to get another 15 hp out of it? How about 150 hp out of a 1000 cc KZ100 motor, think that may ne possible?

Post edited by: steell, at: 2006/01/02 19:56

Mellvis wrote:

Just to satisfy my curiousity, what is the advantage of longer rods? The stroke doesn't change if you use different lenth rods on the same crank (right?), so I don't understand the improvement.

There is not a huge improvement, but every little bit helps

It's easier to understand if taken to extremes, imagine a rod 2" long, as the crank journal swings past bottom dead center it is pushing the rod almost sideways (pushing the piston against the cylinder wall), now imagine if the same rod is 2' long, the rod will remain almost vertical during it's entire travel, so friction will be reduced (always a good thing).
And then there is the degrees of revolution that the piston remains at TDC, the longer the rod, the longer the piston is at TDC (increases cylinder pressure).

Conventional Wisdom states that a longer rod will increase torque, but some experimentation done on a dyno suggests that is not always the case.

So it doesn't increase power do to being longer, but inreases power by making less friction and dwelling at TDC longer thus keeping compression higher for a longer period of time. I get it! (that's what makes me a jenious!)

Hey CB/GS/XS Never underestimate the heart of a KAW. I'm at 88 on a 675cc kz650 now at 13,000.

I routinely run 11,500 rpms on my built KZ650 street bike. With the occasional over-rev to 12,000. The bike has a wiseco 700cc kit, pistons, 29mm carbs, web-cams and ported head. The bike made 78HP at the rear wheel. It's never had an issue related to revs.

The bottom end has never been a problem. It's completely stock (never been apart) and has close to 30,000 street miles. I do however have to replace the cylinder base gaskets every 10,000 miles as it generates oil leaks. I attribute this to the cases flexing at high revs, but am not entirely sure of this. You can buy heavy duty case studs from APE and I'd investigate those for your engine. Torquing the studs tighter might help with this.

On a race bike I would guess you could spin even more revs as you'll need to rebuild it more often anyway. If you can find the mystical Arias 72mm pistions (or have other piston made) let us know about a potential group buy! I'd love a 880cc crazy 650!

With 880cc I would think 110-120 hp RWHP would be available.

You might not also need that much to keep a 130hp CBX behind you. My 80HP 650 will pull an indicated 130mph. The 650 has a much smaller front plate area than the KZ900 or 1000. Looking at it in the garage next to my 900 I'd estimate it's about 75% or less than the bigger bike. Next to a CBX you should have a serious aerodynamic advantage.