Tuning 91-95 ZXRs

Tuning 91-95 ZXRs


I’m currently getting 142 Rear wheel horsepower on my dynojet dyno at 13,200 rpms. 190 at 12,000 with nitrous. 93 ZX7r, this will actually apply to all 91-95s.

I start by having APE modify the crank, lighten by three pounds, and knife edge the throws. This is their 189.00 advertised treatment. They also flute the oil holes for improved oiling. I send my connecting rods to falicon for what they call strengthening. This includes balancing down to 1/10 of a gram and polishing the sides of the beams till they look like chrome. This was 35.00 a piece. All rods did check on my electronic scales to be exact when they were returned. I then set my main bearing clearance at .002 inch. I set my connecting rod bearing clearances at .002 also. I use a combination of Blue and brown bearings to get to this.

I’m currently running 1mm over bore pistons (765mm)total displacement Wisecos Part # R765. I set piston to wall clearance at .002. I set ring end gap at .010. My deck height is .005, I also run a ceramic coating on my pistons that I apply myself, available from POWER HOUSE Products.

I run replicas of the Kawasaki kit cams from APE at 104/107 with intake lash set at .006 and exhaust at .008. I run FLAT faced replica kit valves from APE as well as the kit single high RPM springs with Titanium retainers, all available from APE. With the crank mods and these parts and with a DYna igniton box, you can now turn 14,000 RPMs

I optimize the seat pressure on all my valve springs to give 40lbs at closed or installed height, and 112lbs at open height. I can safely run this motor at 14,000 rpms indefinitely but found that no matter what I try, power ends at 13,200, so I shift there.

I run a (4) angle valve job of 30, 45 seat, 60, and with the important 75 degree bottom cut. I have previously posted bout this. My compression ratio is a true 12.1 .


I run a Dyna 2000 ignition, set with 38 degrees of lead and with a auto retard of -12 when the nitrous kicks in.

I run a Muzzy 4 into 2 into 1 true race pipe with tapered headers. I run a EVAC system on here, I previously posted about.

I DO run a stock airfilter.

OEM Kawasaki flatslides bored out to 41 mm. Jetted as follows,
Needle OCFHP sudco, 4th clip position
Nozzles, purge or Primary, main air jet 200
Mixture screws 1 1/2 out
120 slow air, or 1 1/2 on screw if equipped with..
45 slow air or pilot jet
138 main jet, hex jet not small round jet

I run CR9ek plugs originally developed for the 93 GSXR 750 Suzuki and don’t care that they are resistor. They have another tremendous advantage for a nitrous motor, in that they have such a short ground strap compared to the C9es so they don’t overheat as easily and cause detonation.

I run 100 octane race “PUMP” gas when i can get it. Several stations in Atlanta sell it.

My current engine has 13,000 miles on it with nothing more than 1 valve adjustment and 5 oil changes. Leak Down last tested at 4,3,3,3. I truly believe the occasional blast of nitrous through the motor is good for it. The shockwaves blast out carbon buildup. Nitrous motors are always so clean inside.

Precision engine building “Blue Printing” can unleash a lot of hidden power. As I said before, “ENGINE DYNAMICS ARE THE SAME FOR EVERYBODY”

I’m sure there are other things I cannot think about at this time, BUT I HOLD NO SECRETS!!!

Kenneth Waters

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