The XR600R
Motards by Retards!
When Steve had bought the XR a selection of sprockets and a spare rear wheel had been thrown in to sweeten the deal somewhat, and that extra rear hoop got Steve thinking. Dirt-squirtin’ is all good, well, and fun with a capital grin, but carving up the blacktop is in his blood. No matter how many fire trails he hammered down, with the XR sideways on the revlimiter, trailing a huge curtain of rocks, dust and bits of unlucky small furry mammals that weren’t quick enough to get outta his way, Steve couldn’t shake the mental image of that spare rear rim, wrapped in a sticky road tyre with big dags of semi-molten rubber hanging off the sides. The temptation to turn his new ride into a Motard was irresistible. After his chaotic engine rebuild experience, he immediately asked the rest of the Feral team to help. We were only too pleased to, ‘coz it gave us the perfect opportunity to sabotage the bike. What else are friends for?
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For those who have been living under rocks for the last 15 years, Motards are big single-cylinder dirt bikes, usually four-strokes, which have been fitted with 17” rims, road tyres and huge brakes. They’re light, narrow, nimble and have shitloads of grunt, grip, clearance, brakes and suspension travel. They wheelie at the flick of the throttle, stoppie with ease and jump over any obstacle smaller than a LandCruiser. A Motard will always lose out to a big-bore sportsbike down the drag chute or through high-speed sweepers on an open backroad, but they’re perfectly suited to blasting through city traffic, jumping gutters, running over the neighbours’ cat and fanging tight, bumpy, narrow, potholed mountain roads. They're not about warp speeds, blistering acceleration or superb roadholding. They're about hell fun, big thumps, crazy stunts and getting the back end hangin' out. Motards are almost terminally antisocial – a frequently-aviating front wheel at one end and a deafening thump at the other. In the middle, of course, is the most antisocial thing of all: the rider. Even more so in our case.
The back end of the XR was easy to convert. Take the spare rear wheel, belt crap out of it with a big hammer to get rid of some of the dents and flatspots and add a few new ones, fit a sticky road tyre and play silly buggers with the gearing. Although it's a narrow spoked 18-inch rim, a Bridgestone BT-45 will fit on there. Just. It's only a 120/80 section tyre, the same profile as most modern sportsbike front wheels, but it should do the job. After all, having the rear end step out halfway around a corner is just part of the fun when you’re riding a Motard. Most purpose-built Motards run 150 or 160 section rears, but the XR's swingarm is pretty narrow and there just ain't no way to squeeze a big fat tyre in there. A 17” 140 section would probably fit, but aftermarket rims and respoking cost money, and Steve is a notorious tight-arse.
The front needed a bit more modification. We managed to track down the front wheel from a CBR250R (MC-19) that some poor sod had rammed into a U-turning taxi at high speed. The forks had bent like bananas and the wheel had been rammed back into the exhaust headers hard enough to flatten ‘em. No idea what the taxi looked like afterwards, but it wouldn’t have been pretty. The front end of the CBR looked like it had been dropped out of a B-52 into the middle of Baghdad. Everything that wasn’t bent or twisted was folded, spindled or mutilated, and the front rim had borne the brunt of the impact. It wasn’t expensive, but it wasn’t particularly circular either. Bummer. Ah well, that’s what sledgehammers are for. After belting the rim for three non-stop hours, it was transformed from a pretzel-shaped twist of metal into something that looked almost round. There were a half a dozen big cracks, a couple of flat spots and the rim wasn’t quite perpendicular to the axle, but it was good enough for us.
Once the front roller had been de-pretzelised, it needed to be attached. Preferably in such a manner that it would rotate. With this in mind, we compared the stock XR 21” spoked hoop to the 17” CBR mag to see how similar they are. The result: Not very. For starters, the axles aren’t the same size, so we needed a couple of spacers inside the wheel bearings. Then we needed a few more spacers to get the new wheel roughly central between the forklegs. Give or take a bit. Plus a couple of extra spacers to ensure that the XR speedo drive would talk to the CBR front wheel. Then we chucked in another handful of spacers just for the hell of it. Final count: 346. Nearly as many spacers as the main street of Nimbin on dole day!
Once we’d made sure the CBR wheel was located properly, we crossed our fingers and jammed the sucker in there backwards. Yep, that’s right, backwards. You see, MC-19s wear their front brake callipers on the right-hand forkleg. XRs, on the other hand, dress to the left. After dealing with the bearings and the spacers, this was only a slight problem, easily solved by fitting the front tyre around the wrong way and then mounting the rim with the brake disc on the left.
Speaking of discs, the CBR front stopping rotor is a fully floating, 310mm diameter chunk of high-carbon steel. It’s pretty big, as front discs go. Not the biggest around by any stretch of the imagination, but not too shabby. The standard XR600 front disc, on the other hand, is a bit weedy. It’s only 240mm across, and it doesn’t float anywhere. It does the job, but it takes a hefty handful of brake lever and a few metres more than a well-braked roadbike. It’s great in the scrub, where feel is more important than outright power, but it’s not so handy pulling big stoppies on the black stuff. Funnily enough, the calliper lugs on the forkleg are spaced at just the right distance to mount the calliper on the edge of this pathetic little disc. It’s almost like Honda designed it that way!
We, on the other hand, wanted the calliper to fit onto a 310mm disc. Which meant we needed new lugs. Or maybe a new forkleg. Alternatively, we might be able to get by with just a custom bracket. Enter one large chunk of 12mm aluminium plate and a milling machine. Yes, someone was actually silly enough to let us loose on an expensive piece of precision machining equipment. There’s one born every second!
The mill looked pretty complex, but we got stuck straight into making it go. There’s no point in asking what that lever does if you can just find out by pulling it. After half an hour or so of winding adjusters, pulling levers, grinding gears and bouncing the tool off the bed we managed to drill a few holes, mill off a couple of random chunks of aluminium and spread swarf all over the workshop. Much to our surprise, we also had a bracket that looked pretty good. Right pleased with ourselves, we were. When we carried it triumphantly to the bike and tried to fit it in place our mood soured pretty quickly, ‘coz the damn thing just wouldn’t sit right. In fact, it fouled on the fork leg and the calliper simultaneously no matter what we did. Even a big hammer and some therapeutic percussive adjustment didn’t improve things. After a few minutes of this we stopped whacking the bike and started whacking Steve instead. The bracket still didn’t fit, but we felt much better about it.
Amazingly, we hadn’t completely destroyed the mill and there was still enough left of it for us to have another crack at the bracket. There were some pretty funny noises being made by the time we were finished, though. It sounded pretty sick. Or maybe that was Steve. It can be hard to tell sometimes.
Our second attempt at machining the bracket was much more successfullererer(er). One side bolted onto the original calliper lugs, and the calliper bolted onto the other side. The disc actually slotted in between the pads and the whole thing went around jerkily with a loud rhythmic crunching sound. Oops. Something was still fouling somewhere. It turned out to be the rivets on the disc hitting the stock calliper mount. Bummer. Time for Team Feral vs. the milling machine, round three!
Bridgeport build those mills pretty damn tough. It was smoking and making horrible grinding noises by the time we’d finished with it, but the cutting tool was still going around and most of the levers were still attached. The stock calliper mount was a shadow of its former self (which is a good thing – unsprung weight is evil and must be expunged whenever possible) and the disc rotated without impediment. Now we just had to strap the Crash Test Idiot on board, kick the evil monster in the guts and try out the new front end.
