Words: Jeff Ware Photography: Keith Muir

Back in 1987 the Bimota YB5 was one of the most amazing, expensive, out of this world and radical motorcycles on the planet. It was fast, real fast. It was draped in the highest specification grand prix quality running gear and it handled like a 250 despite housing the lump of an engine that the mighty Yamaha FJ1200 is.

In comparison, the original FJ1200 was a boat.

Almost 35-years later the YB5 numbers don’t even count but the legend of the bike remains and with only 208 units originally made, is as rare as it gets…

So rare, in fact, it took T-Rex Racing’s Rex Wolfenden an eternity to find himself an immaculate low mileage example. But he did it. He got hold of one and landed it on the bench in his immaculate Melbourne workshop that is famous for building championship winning motorcycles, particularly specialising in Honda 750 Fours of the classic Forgotten Era class.

So Rex got his hands on the immaculate and rare YB5 and, as you do, stripped it immediately and began the process of turning into what we think is the only YB5 racebike in the entire world. If there is another, we can’t find it!

The engine was bored 1mm oversize and JE forged pistons fitted to Carrillo conrods, which swing off a lightened and balanced crankshaft on oversized main bearings. The cylinder-head was reshaped and ported by Rex, who also installed oversized IN and EX valves and the appropriate springs and retainers. Rex had some camshafts made to his specification as well. The original five-speed gearbox was undercut and a slipper clutch was fitted to the bike post my test.

Feeding the FJ engine are four Keihin 37mm CR carburettors. Mixture is fired by a Dyna 2000 ignition system and gasses exit via a stunning Over Racing Titanium four-into-one exhaust system and T-Rex alloy muffler.

Rex braced the spindly chro-mo swingarm heavily but aside from that the amazing YB5 frame is standard.

Kayaba 43mm units with T-Rex valving and 1kg springs, slotted back into the original YB5 triple-clamps, replaced the Marzocchi forks. At the back end a custom made to order Ohlins shock was fitted via T-Rex linkages. Wheels at both ends are cast alloy ZX12 items, while the old Brembo brakes were given the flick in exchange for more modern four-piston Brembo calipers. These squeeze SBS race compound brake pads onto semi-floating stainless steel NG rotors via Venhill brake lines – at both ends of the bike. Tyres are Pirelli slicks.

The original fairing was cut up (ouch!) and molds were taken off it to make a set of race fairings. These are wafer thin and ultra lightweight. The single seat unit is a work of art and the way Rex has retained the profile of the original fuel cell cover is a nice touch.

The steel fuel tank was replaced by an aluminium item made by Rex’s equally as talented brother and ex long term Honda Factory Superbike Team Manager Clyde Wolfenden, at C&C Motorcycle Engineering.

THE RIDE

Having ridden Rex’s Harris Honda, I knew the bike would be good. Plus, with such an exclusive and irreplaceable bike, I was not too nervous about the test and damaging the machine as, like the Harris Honda, I could tell by watching it in action that I was going to feel comfortable on the bike within three or four corners. And I was right.

Rex has an ability to make a bike behave in a way that makes the rider confident and comfortable. It’s a knack that takes most of the hard work out of going fast before even sitting on the bike.

With the bike fired up on the roller (starter motor removed) I select first via the reverse shift lever and head out of pit lane. The engine idles high as at this stage there is no slipper clutch fitted. The exhaust note is deep and angry.

I roll out onto the circuit and as expected within four corners my knee is on the ground and I feel like I have ridden this bike many, many times. I’m at home.

I stay out for the session to get photographs for the test and try to use the time to test the brakes, suspension and that stunning engine but there is a rear tyre issue.

On return Rex agrees that the tyre is probably not right and swaps it for a new slick.

The profile lifts the bike and transforms it to heaven on two wheels. It’s a little taller at the back but the tyre is also more triangulated.

The brake package is fantastic and I’m surprised how good the Nissin mater-cylinder works, with good initial bite, feel and modulation at the lever right on lock-up point through the braking process.

Braking hard on turn-in is the best way to get the ultra stable set-up into the turn quickly, along with a heap of muscle. But once that initial turn and commitment is made, the YB5 falls very gracefully on its side with absolute surprise-free progression. If I could get forward more it’d help but I would not sacrifice that original tank profile myself.

It thrives on old school fast lines, which suits me fine.

Cracking the quick-action throttle is just a real pleasure as the perfectly set-up Keihin CRs gently feed on, the cams coming in nicely, plenty of compression and all that together bringing the big 1200 to life. Just before the apex, I could wind it on hard and have it at full throttle exiting the turn. The Pirelli hooking up and driving the YB5 forward. It was like being fired out of a canon!

The front wheel paws for the sky in this situation and as I tuck in and grab another gear on the slick shifting ‘box I can’t help but smile. It reminds me of watching the on board footage of early era superbike races. I feel like Spencer, Rainey or Lawson heading onto the banking at Daytona… I just love these bikes so much. They have true character.

From zero rpm to 9000rpm you better hold on because this Bimota will get you to the next braking zone in a hurry.

The riding experience of the T-Rex Racing YB5 was a memorable one and a true pleasure. I would not change it much at all, if anything, a tiny bit more raceable in the steering but that might take away the rock solid stability.

If only Rex was mass-producing these amazing motorcycles – I’m sure there’d be 40-something year-old riders whipping credit cards out all over the world…

Stunning. There is no other word for it.

SPECIFICATIONS

ENGINE

1988 Yamaha FJ1200 engine, standard 63.8mm stroke, 1mm over 78mm bore, 11:1 compression up from 9:1, polished and modified standard crankcases, lightened and balanced crankshaft, Carrillo conrods, JE forged pistons, T-Rex Racing camshafts, T-Rex Racing cylinder-head porting and reshaping, oversized EX and IN valves, standard oil cooler and galleries, standard five-speed gearbox with gears undercut, slipper clutch, Dyna 2000 ignition system, Keihin 37mm CR carburettors, Over Racing Ti exhaust system, T-Rex Racing muffler.

CHASSIS & BODYWORK

1988 Bimota YB5 double cradle chro-mo frame and swingarm with T-Rex swingarm bracing, 43mm KYB forks with T-Rex valving, 1kg springs, 7wt oil, Ohlins custom made shock, 11kg spring, Brembo four-piston calipers, NG semi-floating rotors, SBS brake pads, Venhill line, Nissan master-cylinder (f), Brembo caliper, NG rotor, Venhill line (r), Kawasaki ZX12 wheels 3.5 x 17in, 6.00 x 17in, Pirelli slicks, C&C Engineering levers, rearsets, handlebars, fairing brackets, alloy fuel tank, remade Bimota bodywork

PERFORMANCE

150hp-plus at the wheel, 182kg dry

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