Broxy grabs multi NZ Champion Brad Groombridge’s championship-winning RM-Z450 to find out just what makes this bike so versatile.
Luke Temple is one of those guys you can’t help but get along with in the moto paddock, but he has a bit of a secret affliction, an addiction to all things Kawasaki…
Words and Pics: Mat
If you’ve ever had a mate who passed all his exams at school without studying while you sweated blood over cram sessions, well, that kid is kind of Luke in the moto paddock.
Instead of building his way up the ladder of power, Luke graduated straight from juniors to the big leagues when he bought his first KX450F, but it was the old KX500 that stuck in his mind…
There is an unmistakable allure to the big 500cc, 2-strokes of the 90s.
Maybe it is the huge expansion pipes, the blocky plastics, or maybe it’s the insane power. Whatever it is, Luke Temple is a man who lives the KX500 life, but getting his own example of the mighty KX wasn’t without its challenges.
“I’ve been wanting to build a KX500 for a few years now,” Luke says. “But every time a decent one popped up, I always found an excuse why I shouldn’t buy it.”
That bad attitude wasn’t to last though, and it wasn’t long before a bike popped up that Luke couldn’t say ‘no’ to.
“Earlier this year, around March, I found a really good clean 2000 KX500 that came out of California, and I finally just decided I should get it or it would never happen; you only live once, right? Next thing I know it’s in my garage.”
With our winter slightly soggier than normal this year, it gave Luke plenty of time to fettle the big 2-stroke thumper back to perfection.
“Slowly over winter, I spent my days looking for every aftermarket part I could get my hands on and even had some custom parts made. I got in touch with Sean Collier in America, who put me in touch with the team who built the KX500 that he won the 2-stroke Nationals with at Glenn Helen.”
Along with the special custom touches, Luke also raided his more modern Kawasaki parts bin.
Incredibly, even with 17 years between the heroes of the Kawasaki dirt range, the air forks from a 2017 KXF450, bolt right up to the existing KX500 triple clamps; so naturally, they went on – along with most of the KX450F front end, including the far more modern brake discs, with Luke rebuilding the stock KX500 calipers using new KX450F internals.
The wheels also were pinched from the KX450F, but considering the standard KX500 axle is an 18mm unit and those on the new bikes are up around 25mm, Warp 9 Racing in America was called and they made up the necessary spacers to ensure the rear wheel would fit.
The rear wheel also required a custom brake disc as well, which Warp 9 also made for Luke’s project.
While the front end is completely up to date, the stock rear shock has surprisingly been left in place – mainly due to the fact it tapers downward with just enough space to suit the exhaust – but Luke had a card up his sleeve to get more value out of the 17-year old shock.
He gave Mark Patterson Suspension a call and instructed them to throw every aftermarket RaceTech component at it they could.
The result is a bike that actually rides pretty well, according to Luke, and going by his performance at the Sand Prix, he isn’t lying!
While the engine is mostly stock, Luke has ensured it’s ready to take a good fang with a fresh piston, rings and a full aftermarket exhaust.
The only true modification surprisingly doesn’t produce any extra power, but instead makes the beast easier to kick over. Remember, this is a bike from a time when real men kicked their bikes to get them going.
“I’ve had an auto decompression diaphragm added to the head, which feeds off the vacuum created from the reed valve.”
This little mod makes the big 500 kick-over like a 125, and it’s hilarious to think that it is, essentially, a valve off a Briggs and Stratton lawnmower.
“The only other engine mod is the one-piece clutch cover that I have cut off, I’ve had a space plate machined up and attached my 450 Hinson clutch cover. This looks cool, and now I can get at the clutch easily.”
Finishing off the build was the obligatory graphics upgrade, which Cam Huggins from DB Graphics made up, while DR Trim in Morrinsville recovered the seat to match Luke’s 450F.
But we don’t spend all that time in the shed just to sit back and admire what we’ve put together, we build bikes to get them dirty – and Luke is no exception.
“Once the bike was built up, I rode it at Mercer at a practice day, thinking the bike would suck. It would look and sound cool, but ride like a bike would have done in the 90s.
“To my delight, it actually rode really well – nowhere near a modern 450, but pretty good nonetheless.
“Once the Mercer Sand Prix came along I thought, ‘why not have some fun and ride the 500 instead?’ I’m a bit past the days of racing nationals and trying to get good results. Nowadays, I ride for fun, so I thought: ‘why not race the 500?’ I ended up doing really well on the old girl and came home in 5th.”
Not bad for a bike based on a design first penned in the early 80s.
But the coolest thing about this bike is the number of people that come up and drool over it. It seems everyone – no matter their age or background – can appreciate the old 2-stroke Kawasaki.
“It must be a nostalgia thing or something, but people just love to look at it,” explains Luke, and we’d have to agree.
Suzuki has released full technical details of its 2019 RM-Z250, with the MX2 machine getting a new frame, swingarm and suspension, plus a new engine that produces more power and torque than its predecessor. The new RM-Z250 also gets the latest version of Suzuki’s Holeshot Assist Control and traction management systems, further improving its performance, while more angular new styling sharpens the look.
The engineers at Suzuki have been busy and the engine has been enhanced for both power and manageability, with a plethora of upgrades.
The top-half of the engine is redesigned with a new cylinder head, intake and exhaust ports. The intake-cam profile has been changed to increase valve lift and improve throttle response across the whole rev range. They have also decreased mechanical loss by redesigning the cam-chain and tensioner.
Probably the most impressive of the engine upgrades is an added second injector nearer the air-box to increase power, higher in the rpm range. To get all this new grunt to the back wheel, Suzuki have changed the gear-ratios on the second and top gears.
To complete the engine side of things, the 2019 RM-Z250 receives an extension to the exhaust by 99mm, improving power at lower engine speeds.
The frame has been put on a diet and has lost 370g whilst being stiffened up 10%.
The ergonomics have also been changed to improve the bike’s handling performance and agility. The Suzuki receives new Renthal handlebars which are straighter, lower and further forward from previous models. The footpegs have been moved forward and higher whilst the fuel tank has also been on a diet, which saves 312g, while a slimmer seat loses another 274g and makes it easier for the rider to move around.
The KYB Spring-fork suspension, bigger brakes and lighter wheels have also helped to improve handling performance.
As with most new machines, the electronics package is a focal point and the RM-Z250 is no exception.
Suzuki’s advanced Holeshot Assist Control and traction management systems are further improved for 2019, giving riders a better chance to get out of the gate ahead of the competition and stay ahead in the race. Suzuki Holeshot Assist Control (S-HAC) was developed to give riders an advantage out of the gate, optimising ignition timing to help the launch be as efficient as possible. Two modes either advance or retard ignition timing, with riders able to select either depending on the surface.
For full details check out the next issue of Dirtrider Downunder!