SUPERCHARGED KWAK CHOP
– IT’S A CHOP, WITH A SUPERCHARGER… WIBBLE
SUPERCHARGING IS, Y’KNOW, NOT JUST THE PRESERVE OF TOP FUEL DRAG RACERS, HIGHEND GERMAN SALOONS, AND MAD MAX’S COMPANY CAR; KAWASAKI’S RANGE-TOPPING H2’S GRABBED THE HEADLINES IN THE LAST FEW YEARS, BUT THERE’VE ACTUALLY BEEN A FEW SUPERCHARGED TWO-WHEELERS PREVIOUS TO THAT, INCLUDING PEUGEOT’S JETFORCE – YES, A SCOOTER, AND A 125CC SCOOTER AT THAT!
You’ll have seen Simon Humphrey’s CB flat tracker in the last issue, and you may remember his glorious XS650 from a couple of years ago too. Well, when I went up to Scarborough to photograph that Yamaha, he had on the bench a Kawasaki GT550 project that’d been initially inspired by another GT that he’d built a few years ago that had won several trophies, including at the Farmyard Party. This particular one, though, was set to be a little more radical, with girder forks and a whopping great supercharger squeezed behind the cylinders!
The original old and battered Kawasaki GT550’d been given to him in return for painting a few parts for a friend – useful as he was running a GT at the time, and needed a few parts off it (such as the rear tyre that had all of half a millimetre of tread on it… more than half a millimetre more than the one he had on his own GT – “I was being all eco-friendly… or tight – same thing!”).
Some time after the poor bike’d been robbed of spare parts, he realised it’d actually be a great basis for a project. To decide what else to use, he chose by the simple expedient of spinning around in his garage with his eyes closed, pointing his finger, and opening his eyes! A few spins resulted in a supercharger from a modern Mini, a 1.5”
SU carb from a classic Mini, some random rolling gear, and a pair of girder forks, and a plan was put in place – a hardtailed Gee Tee with a supercharger! (Just thinking, that’s some garage – if most of us did the same thing in our garages, our bikes’d probably be built from several tents, a number of old paint cans, a few ancient spanners, and a cobweb…)
First off, he needed to make a frame, and he used his usual method of mounting a pair of bottom frame rails on box section two inches thick (thus giving a two-inch ground clearance), and then fabricating the rest of the frame from scratch to suit the 15” Yamaha rear wheel and the girder forks (yes, I know, bear with me!), with various sections running from round to square (check out the frame around the rear wheel spindle), and with integral blower mounts as part of the frame (and have you noticed the neat way the lower frame rails sweep inwards to the rear of the engine, and then out again to go around the rear wheel?). The frame was finished, with the matching angular fuel tank, electrics box, and rear mudguard, and they were all painted in a subtle black/brown/green ’flake (that you’ll just have to trust me about as the grey light of winter doesn’t exactly show that here).
Then, as with the CB last issue, his enthusiasm ran out or, to be more accurate, other projects started to get in the way and even though the Kawasaki remained clamped to the bench, getting the occasional halfhour spent on some of the many and varied detail pieces, it even stayed there when he moved his workshop! After about a year, still clamped on to the same work bench, in the new garage, he got enough projects finished and out of the way to be able to devote a little more time to getting the GT finished. In order to kick-start his enthusiasm he thought that with a quick rewire it might even start up and give him the drive required for the final push. No-one, least of all Simon, could’ve expected the bike to fire into life at the first press of the starter, yet that’s exactly what happened, easily boosting to 10psi with the guesstimation of running a 1-to-1 ratio with the supercharger pulleys proving ideal. The fact that the belt didn’t immediately jump off and whip him across the face shows that he did a great job of aligning the pulleys and tensioner as well!
The joy of a perfectly running supercharged motorcycle was short-lived though when he took a brief test rid. “After attempting to ride down the yard and nearly ending up on the wrong side of a hedge, it was clear that the girder front end wasn’t going to work. It handled like a puppy on a lead, and crossed with a supercharger and a car rear tyre, probable death!”
After a number of rather extreme swear words the Kawasaki was banished to the bike lift for another six months, and the girder front end was replaced with a conventional telescopic fork front end, albeit one with a modicum of looniness in that it’s a skinny set of CG125 forks, with a bespoke caliper mount and a pair of groovy chain handlebars, and that was it – all finished.
Mere days after these photographs were taken though, on one of the darkest days in February, with snow showers and a harsh north-easterly blowing in off the North Sea, the little GT was sold and went off to its new home, with Simon not really having had the chance to spend any time on it on post-Covid roads. And while he’s stated that he’s not going to be messing about with bikes for a while, relying on his mildly-tweaked Big Twin for his two-wheeled kicks, I can near guarantee that he’ll be getting itchy spanner fingers soon, and that there’ll be another crazy creation being assembled in his workshop before long!
ENGINE:
Kawasaki GT550 engine, notched head fins, debadged rocker cover, BMW Mini supercharger, Austin Mini 1.5” SU carb, one-off plenum chamber/ inlet/wrapped pipes/blower belt drive from ignition cover, one-off hardtail, Öhlins steering damper, one-off forward controls/hand-shift, Honda CG125 copy forks, Honda Super Dream import wheel, one-off brake stay, one-off chain ‘bars, underslung brass mirror, one-off coffin tank with back bones/glass fuel sight gauge, hand-made leather seat with brass rivets, one-off rear mudguard, Yamaha Drag Star rear wheel/ disc, one-off drive shaft, AP Lockheed caliper, 195/65x15” Kingstar car tyre, one-off electrics box/bespoke loom, vintage brass Bates headlight
FINISH:
Gold ‘flake with green candy/black fade bodywork & frame moulded with wood-grain paint/24 carat gold leaf by owner at Total Alloys (www. totalalloys.co.uk)
ENGINEERING:
Owner