This article was written by Steve Klose. Last updated 1.21.16 (base gasket information).
The Kaw Turbo can be a lean, mean, Ninja-stompin' machine, but unfortunately the emphasis can too often be on the "lean" part of that description, which is at the heart of most problems with the blown GPz.
First off, many Kawasaki Turbos came from the factory too lean-burning to even idle properly. Another symptom of a lean burn is a noticeable stumble off-idle. Fortunately you don't have to live with a "bucking bronco" Turbo.
The cure is rather simple. Backout the four tiny screws that secure the Throttle Position Sensor (TPS) cover (unscrew each a little at a time - they're designed to stay in the cover). The TPS is attached to the right side of the fuel injector throttle bodies and the cover has the silver "DFI" insignia. Notice that the TPS is held in place with two adjusting screws with a glob of yellow paint on each head.
With the engine fully warmed loosen the two adjusting screws just enough so the TPS can be rotated. Now simply turn the TPS (turning to the right richens the mixture - to the left leans it out) in VERY small increments (it's an extremely sensitive sensor) until you find the spot where the engine idles best. Turning the TPS to the right also raises RPM so you'll have to lower it by turning the throttle adjustment knob on the left side of the throttle bodies. Keep rpm at about 1,000 to 1,500 during this adjustment. When you've found the "sweet spot," tighten the adjusting screws, reinstall the cover and take a road test. Chances are that's all you'll need to do to cure the low-speed bucking.
If that doesn't work the bike may need an adjustable fuel pressure regulator. These are available from Mike Chestnut of Horsepower Unlimited (615-824-6116) for about $90 and your old regulator. By playing around with the adjusting bolt, which unfortunately is at the bottom of the regulator making convenient adjustment difficult, you can raise the fuel pressure to the injectors thereby richening the mixture. This is a sure-fire cure for stumbling Turbos that won't respond to TPS adjustment.
High-mileage Kaw Turbos (over 35,000 miles) that are experiencing erratically fluctuating idle speeds most likely are in need of a new TPS. If you're constantly adjusting idle with the left-side throttle adjustment knob and can't seem to keep the idle steady this is more-than-likely the culprit. Check your service manual (you do have one, don't you?) for the TPS diagnostic procedure. It's quite simple and can be accomplished with a hand-held multitester in 5 to 10 minutes. New TPSs will set you back about $300 (ouch). If you're lucky you might be able to find one in a salvage yard or on ebay for half that. And no, a TPS from an old fuel-injected GPz1100 won't work on your 750 Turbo.
Manifolds (the rubber boots that hold the fuel injector bodies to the cylinder head) are prone to cracking (especially on the non-visible side that mates to the cylinder head) and leaking. A telltale sign is a mist of fuel around the area of the manifolds. You'll have to remove the surge tank and disconnect the throttle bodies to gain access to the manifolds. Expect to do this about every 20-30,000 miles. Chestnut stocks these at about $10 each.
Sticking cam-chain tensioners are another weak point on Kawasaki 750 Turbos. Symptoms are a rattling or knocking sound emanating from the top of the engine that lasts initially for 2 or 3 minutes shortly after start-up. The noise interval increases the longer you ignore it so this is one service that's best taken care of promptly. Dismantle the entire tensioner assembly and if no parts are excessively worn you can probably sand the "wedge" and the "plunger" surfaces with 400 grit sandpaper until smooth, lube everything up with high-temp grease and reassemble it. But I always feel better replacing the two pieces along with the two tensioner springs with new parts for about $50 (don't forget to replace the cam-tensioner gasket). If you can do without an automatic tensioner Horsepower Unlimited offers a mechanical one for about $40. Others are available on - you guessed it - ebay. Expect this problem every 12,000 to 20,000 miles.
A few Turbo gas tanks are known to seep fuel along the surface where the "tang" is brazened to the back underside of the tank. Mike Chestnut of Horsepower Unlimited says JB Weld will do the trick, but I prefer to have the junction re-brazened at a radiator repair shop (no more than $50). But first get a guarantee from whoever is doing the brazening that the tanks topside painted surface won't be harmed. If he shrugs his shoulders, scratches his head and says, "Well, I'll try my best," find someone else. If you're in the market to buy a 750 Turbo any you're likely to come across has already had this procedure done so don't sweat it.
Continuous drive chains are recommended for the Turbos. Riveted master links are your next best alternative. If you prefer a press-fitted master link chain have the link welded or check it often. Kaw Turbos love to throw out master link clips which allow the link to back out and smash into the chainguard and/or the shift mechanism cover.
Oil cooler lines are prone to seeping. Replacement lines are no longer available. Ebay or your local hydraulic hose repair shop are the only options. Lines usually last between 25,000 to 45,000 miles.
Check the sidestand pivot bolt often. It backs out easily.
Swingarm bearings came from the factory with very little grease. Unbolt and remove the swingarm pivot shaft and grease the bearings inside the swingarm liberally. Be sure to torque the bolt properly (72 ft/lbs., 10 kg/m) upon reinsertion. If the bearings were never greased since the bike was new this little trick should improve handling in a big way.
That rattling sound in the tailpiece is probably the sign of worn computer support bushings. Replace them (about $8 each and there are three). You DON'T want your expensive computer bouncing around on your rear fender.
Engines are exceptionally durable - abuse them as you will. But after a hard run (or any run for that matter) it's best to let the turbocharger "cool down" for about 30 seconds to a minute before turning off the ignition. Change the oil often (every 1,500 miles) and the turbocharger should last you about 50,000 miles or more.
The Kawasaki clutch friction plates are virtually indestructible and can stand up to all but the very worst abuse. Mike Chestnut attributes this to the use of whale oil in the manufacturing process. Whatever the reason, O.E.M. plates are your best bet (in the unlikely event your plates need replacing). There are simply no better aftermarket plates for the Turbo than those made by Kawasaki. Clutch cables never need adjusting. Don't know why, can't explain it, just accept it. I still like to replace mine every 15,000 miles (just stubborn I guess).
Some Turbo owners -- especially those who have installed the big-bore 880 kit -- have experienced seeping cylinder base gaskets. My own stock Turbo starting moving oil past the base gasket at about 60,000 miles. Kawasaki has upgraded the part; first to a steel gasket, and now, according to Charlie Brown of Evergreen Turbo, to a rubber-coated steel gasket (part# 11060-1726). Order one and have it ready when the inevitable occurs.
If your LED fuel tank gauge won't light all the bars on a full tank it's likely be one of two things: the float coil or the sensor lead plug contact is corroded. Check the sensor lead contact first (it's far simpler and the more likely culprit). It's that little lead wire you always forget to un-plug when you remove the fuel tank (sometimes just un-plugging and re-plugging the lead does the trick). If that doesn't work you'll have to remove the float and GENTLY clean the contact coil with 400 grit sandpaper. With the float removed now's a good time to flush any rust from the tank.
Owners of high-mileage ZX750 Turbos (70,000+ miles) should check their clutch basket dampers. The sign of failure is seeing tiny bits of hard rubber in your oil during a change. Pull the clutch pack, and clumps of this crap should be readily apparent in the basket. It's designed as a non-serviceable unit and a new basket is no longer available from Kawasaki. What to do? Well, a guy in Finland, Juha Tanila, sells a kit consisting of the six dampers, a new back plate, and screws to replace the original rivets. You grind off the heads of the rivets, drill or bang them out, install the new dampers, cut threads in the basket posts and screw in the new back plate. TA-DA!!! Well, almost. Some Germans are reporting the polyurethane dampers break down in as little as 20,000 km. (12,300 miles). Not good. Another guy in Australia named Jamie Summer sells neoprene dampers, which he claims are very durable. You could combine the two kits and hope for the best. To add to the mix I'm once again offering dampers cut from Viton and still have a few kits left to sell (Steve Klose). Yes, I've installed them in my own 750 Turbo. If those aren't enough options for you, and you'd rather have a professional rebuild your clutch basket on an exchange program, contact Roger Twito of Tennessee. Roger uses a material called Delrin for the dampers and has been rebuilding Honda CBX clutch baskets with the stuff for years.
Now, go out and stomp a few Ninjas
© Turbo Motorcycle International Owners Association