The 41-year-old nuclear research engineer from Berkshire, west of London, has good reason to be pleased with his unique, hand-built machine. At first glance it looks almost like a standard version of the gigantic KZ1300 six that Kawasaki released in 1978/1979 in the rush toward ever larger and more powerful superbikes. But this particular machine is considerably bigger; it includes two complete KZ1300 cylinder blocks grafted together to make a 70-degree V-12.

If you know anything about Millyard and his history of building bikes—especially old-style Kawasakis—with more than their original number of cylinders, the V-12 Kawasaki won't come as a complete surprise. After starting this wacky process by creating Honda V-twins using a pair of C90 and then SS50 cylinders, he produced a string of Kawasaki two-strokes with four-, five- and even six-pot powerplants based on the old air-cooled triples. Then he built an even more ambitious special, a 1600cc V-eight compiled from two four-cylinder KZ1000 engines (which we profiled in September '02).

It was while at a classic bike show with that V-eight that Millyard hatched a plan to go a stage further with a KZ1300-based V-12. It wasn't even Millyard's idea. "I was there looking after my V-eight, and there were a couple of KZ1300 crankcases for sale nearby. Some guys saw the cases and said, 'Suppose you're going to make a V-12 next, then?' I said no, I wasn't, and they replied that it would be impossible anyway. Of course, as soon as they said that, I had to build one. I spent the next two days thinking about how I was going to do it, and by the time the show ended I'd worked it out."

Designing and building the V-12 required plenty of thought even for Millyard because this project was far more ambitious than the V-eight. The creation of the engine was similar in that he once again retained the original cylinders as the front bank and grafted on a second set at the rear using a shared crankshaft. "The original cylinders are only five degrees from vertical," Millyard says, "but I wanted to make this engine symmetrical, so I set both banks at 35 degrees from vertical to give a 70-degree V-12."

Creating the V-12 was made much more difficult by the six-cylinder engine's lack of internal symmetry. "The rear head is cut and reversed, and runs backward, but this caused a nightmare because the KZ1300 cams and sprockets aren't in the middle of the engine, as they are on the KZ1000," Millyard recalls. "The stud positions are slightly different and the cams are offset. So I had to cut away all the water passages and oil galleries, then remake them, plus the cam-chain tensioner and new cam runs. I made a cam chain from two heavy-duty Hyvo chains welded together. It's about six feet long—taller than me!"

The only thing smaller than standard is the engine's stroke, which is reduced from 71mm to 63mm using flywheel weights from Kawasaki's 750cc H2 triple. "I wanted to reduce a bit of stress in the engine and also have a roller-bearing crankshaft," he says. "The KZ1300 had some problems with its plain bearing crank and I didn't want to make it worse, so I converted it all to roller bearings so I can pump oil through even at low pressure."

Retaining the original 62mm bore gives a capacity of 2281cc. Pistons, valves and camshafts are standard, though cam timing has to be slightly out because the cams aren't quite symmetrical, and don't run backward perfectly. "I've probably lost a few horsepower, but that doesn't matter. The standard KZ1300 made 130 hp, so this engine has the potential to make 260!"

A more serious problem was that the liquid-cooled six, though huge, has a more modern and compact crankshaft design than the KZ four, so Millyard could not repeat his V-eight trick of using pairs of side-by-side con-rods. Instead he designed new rods based on radial aircraft engine practice, with the front one of each pair of cylinders using a master rod, to which is attached a smaller secondary rod for the rear cylinder.

"That was the only drawing I did on the whole bike, using cardboard templates," Millyard recalls. "The con-rods were the hardest part of the engine. Everything's so narrow and there's very little bearing area, so I had to use the strongest material I could." Finding the required grade of high-tensile chrome-moly steel proved difficult. "I had to buy five-inch-diameter round bars, then machine a 20mm thick plate out of the center, so 90 percent was wasted. I couldn't cut it with a saw, and it would have taken months on my old milling machine. But luckily my friend Chris Halliday of Pretech (who supplied the bike's brakes) offered to do the rods on his CNC machine."

Fuel injection is from a late-model KZ1300 Voyager, and is improbably close to standard, though Millyard added some volume switches from a radio, which allow the system to be fine-tuned. He built the exhaust system himself using various cheap pieces of a car exhaust. "It's a straight-through system, basically four 3-into-1s linked up. It's designed so I can fit standard silencers, but I don't want to because it'd be far too quiet."

Plenty of other standard Kawasaki bits have found their way onto the beast. The starter motor, alternator and regulator are all late-model KZ13 items. The radiator was made by taking two standard aluminum units, cutting the top off one and the bottom off the other and welding them together. The system is plumbed with a large-bore central heating pipe, and uses a rally car electric pump to keep coolant circulating whenever the ignition is switched on.