KAWASAKI ZRX1200R TURBO
Aussie CMM reader Derek Henderson had a dream: an ELR replica, but it was not to be. Instead he picked up a 2001 ZRX1200R, put a turbo on it and made it a T-REX! Bliss!
Reader Derek Henderson’s amazing 200bhp Eddie Lawson replica!
When Eddie Lawson won the AMA championship on that gorgeous KZ1000S1, which led to the birth of the Z1000R replica, that was ‘my period’. It was 1981 and I was 19. I wanted one so badly back then, but it was out of my reach on apprentice wages, then life got in the way. It’s a common story.
Fortunately, Kawasaki knew there was a bunch of die-hard tragics like myself that missed the opportunity in their youth and so released the ZRX in 1997. Undoubtedly, a better bike in every way to the Z1000R of 1982, or even (dare I say), the exotic, rare, and highly valuable Superbike Championship winning KZ1000S1 it replicated, a fact that even a tragic like myself can’t argue. Anyway, circumstances had me waiting for the upgraded ZRX1200R and this particular bike is my 2001 model (with a twist), which I bought new in 2002.
You see, in Australia, we had a different livery of ZRX1200R every year; that’s all that changed from 2000 to 2008! Though it wasn’t until 2008, the last of, that we got the bike in the true Eddie Lawson Replica livery. So this bike has been fitted with that bodywork and my 2008 model ZRX is now red in the GPZ livery. That in itself is a long story, but let’s just say, Eddie’s bike had black wheels, gold brake calipers, black frame, silver swingarm, black forks and gold shock reservoirs, as did the 2001 ZRX, but not the 2008. The latter only had the lime green
livery right. So the ‘bodywork’ was duly swapped to my 2001. To get the rest right you have to buy the earlier ZRX1100R, which has the black engine covers, just like Eddie’s KZ1000S1. This is how it all started, building myself a modern day Eddie Lawson Replica, replica. Old school look with new-age ability – the best of both worlds.
In my opinion the ZRX is a highly underrated bike; it’s quick, purposeful and comfortable. The motor is bullet proof and is the same base unit as was earlier fitted to the ZZ-R.
I’m not completely sure how the turbo decision happened, but I definitely wanted more sportsbikelike performance out of the ZRX; the simple answer was a turbo! Research informed me that a nigh-on stock motor is strong enough for 12psi boost, well north of 200 rear wheel horsepower and an earthmoving 150lb-ft of torque. Time to order a turbo kit from the US, which was under $5000.
After much head scratching (some of the kit parts were missing) I finally got to work. The most important thing to start with on a turbo build is the position of the turbo, and the exhaust header supplied with the kit, on the second attempt, after much modification to fit the outlet ports of the motor, I did just that. Getting oil to and from the
turbo is vital: while the ZRX is basically a ZZ-R motor, a ZZR has an oil-cooler, a ZRX not. So all the plumbing and ports exist within the sump pan and you just need to know what you’re doing and tap into it. So no scavenge pump is required, as the turbo gets oil to and from the motor by what exists, with some external hoses and non-return valves added. There was an additional mod made to the sump to better supply oil to number 2 and 3 main bearings, which is a weakness on this motor and loading up the crank with all these extra ponies, well, it seemed like cheap insurance to me. Hoses in the kit were cheap and nasty, so I made up the Aeroflow braided oil lines with full flow fittings you see.
The turbo is a Garrett T3 with external waste-gate, fitted with a Turbosmart Ultragate 38, and that set up all fits in and works pretty well. The turbo is bush-bearing, not roller-bearing, and as antiquated as that sounds, it’s not a bad idea on a big-bore four cylinder bike.
Ball bearing turbos spool up really quickly and have boost coming in at really low rpm. That’s perhaps fine on a car, or a big lazy twin, but as you may know a ZRX is no slouch below 5000rpm in stock trim. Boosting that bottom end on an already strong motor would see some scary corner exits. I wanted the bike to have the same low and mid-range manners. This big oversized lazy turbo we have here spools up pretty slowly, bringing boost in from around 5000rpm, when things start getting a bit
manic! The big turbo also compresses up pretty cool and no need for an intercooler.
Carbs are stock with some mods. My other ZRX with a four-into-one and K&N filters runs sweetly with 135 mains: stock is 95. This turbo bike runs 108 mains! How so? Well, it had me baffled at first too. But the wide band air/fuel analyser I fitted gives you the facts. That, incidentally, didn’t come with the kit and is the single most important thing you will need in setting this lot up to perfection. My tip: for every one right answer available on the web, there are 10 wrong ones!
The build of the bike seemed to take forever and I always seemed to need something – a hose, a bracket, a fitting, a bolt. It was a long, slow process, the good part of which was that I really didn’t notice the money disappearing, or maybe the wife didn’t. With all this ebay shopping, one thing leads to another. A couple of beers later and you are ordering Hel brake and clutch lines, anodised bolts and other such blingy stuff, Pazzo levers, wheel tape, decals and the like. It seemed every few days there was a package arriving from somewhere in the world.
I even splashed out on a custom-made Corbin ‘Holeshot’ saddle in carbon-fibre print leather, which I think really finishes off the ELR look I was chasing. Ohlins springers are next! All I can say (cost wise) is the bike is still cheaper than a new superbike… and more original!
Dyno time! My first day on the Dyno showed up a few basic issues. Firstly that the bike was way too rich. Secondly that the Mallory Fuel Pressure Regulator wasn’t doing the job, and finally the plenum and intake system was blowing off at 4 or 5psi. What else we discovered was that the bike was already developing 165bhp and 124lb-ft of torque on the back wheel! To put that into perspective, the bike stock is 122bhp and 82.6lb-ft on the crank!
The fuel pressure regulator was changed out and the plumbing redone to suit. I made up the plates you see between the plenum and the frame to prevent the plenum from blowing off under pressure. I bought and fitted the wide-band air-fuel analyser, and I started changing jets and carbie settings endlessly, with endless test rides. Eventually it was perfect, even if it scared me a bit spinning the rear in third. That brought on a decision to fit heavy-duty clutch springs! So I have since fitted Barnett clutch springs to the otherwise stock clutch basket.
Testing the bike on the road and trying to study the gauges to check the set up was bordering on suicide. The only way forward was to set up a Gopro on the tank to look at the gauges, take the bike down to ‘Race for Real’ night drags at Eastern Creek, and study the video after each run. This I did. The bike ran awesome and the fuelling was perfect. Have a look at the Youtube link https://youtu.be/ kdkw6p4-wt0
Now remember these are proving runs. I’m not really giving it the berries and you can see I am mostly short shifting around 8000rpm! There is a lot more in there at 5psi, particularly on the launch!
Turbo lag doesn’t exist on a big bore bike like the ZRX; there is power and then there is more power. When you are running pinned through the gears, like on the drag strip, you don’t feel the turbo coming in, it’s just like a very quick bike as the boost is on max and doesn’t move, or drop off from second gear to top. On the street, wow, you feel that boost coming in! I fitted a quick-shifter to eliminate the (little) lag during gear changes. The Turbosmart Ultragate is a very clever design waste-gate and is a combination, dump-valve/pop off valve. It maintains the pressure in the system perfectly and drops it off as soon as you close the throttle.
With the fuelling sorted it was back to the dyno for another run, this time with a 10psi spring in the waste-gate! 202bhp and 147lb-ft. The 10psi spring only indicated 8psi pressure in the system, so I now currently run a 13lb spring which gives 10psi. So I’m guessing maybe 220hp? Whatever, there is more than 200 on the rear wheel and that was my goal.
The bike as you see it in most of the shots is fitted with stubby dump pipes as were supplied with the kit, which are remarkably quiet. The turbo actually quietens the exhaust as it spools up, though try telling that to the Highway Patrol! Nice and tidy as they are at the end of the day, it doesn’t fit my Eddie Lawson Replica ‘replica’ objective.
I have since home-made a ‘period correct’ Kerker megaphone from a 1980’s AMA Kerker tail pipe, which I found online.
My goals were to build a bike with high attention to detail (it won Best Japanese Bike in a show down here). I wanted it to produce 200bhp (it now puts out 202bhp) and I wanted to run a quarter under 10 seconds: this goal is a work in progress!