The Irving Vincent 1300
(Page 3 of 5)
March/April 2008
By Alan Cathcart
The first Irving Vincent sidecar appeared in Barry’s hands in January 2004 and duly won the New Zealand Historic title a year later, as well as the prized Ken McIntosh Trophy for excellence in motorcycle engineering. This was followed by the fuel-injected 1,600cc jumbo Irving Vincent solo in February 2005, and 13 months later by the fourth and latest in the crop, a 1,300cc classic racer with a plain-bearing engine built to compete in the Period 4 category of Down Under historic racing.
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Sharing the wealth
Response to the project has been so overwhelming that Ken and Barry have decided to start a limited production of 10 bikes a year in either road or race guise for customers around the world. “We don’t want to make any headaches for ourselves by making promises we can’t keep,” says Barry. “We enjoy what we do, and plan to keep it that way. But a de-spec’d version of the race bike would be within our capabilities, and that’s what we’ll be working on next — though there are no promises as to when it’ll be ready. We’re not taking any orders!”
Engine no. IV-0004 of the six built to date powers the latest evolution of the Irving Vincent species, our feature bike, and is the only one so far to run on gas in preparation for the Irving Vincent street version café racer that’ll appear next (though for race purposes, it’s since been converted back to methanol). This is an under-square, long-stroke 1,295cc version of the brothers’ externally faithful recreation of the 50-degree V-twin, high-cam, overhead-valve Vincent dry-sump engine. It was created entirely in Australia by K.H. Equipment, with heavy duty crankcases with provision for fitting a Nippon Denso starter motor and alternator for the street bike. The plain-bearing crank and Carrillo rods are made in EN26 steel, with Nikasil-bore cylinders housing JE pistons running a hefty 14:1 compression.
While the heads fitted to the test bike are the original-spec design with stock 65-degree included valve angle, new big-port cylinder heads have been designed by Ken Horner for the 1,600cc engine that feature a much narrower 50-degree valve angle. “In terms of cam profiles and combustion chamber design, we just treat it as one-quarter of a V8 Supercar motor,” Ken says. “That way, we can plug into acquired knowledge of all the people we know who work on those engines.”
This meaty engine is installed in a modern chrome-moly replica of a period Vincent spine frame, with the three-liter oil tank incorporated in the backbone. A set of 38mm Ceriani forks — fitted with Kawasaki motocross dampers and Ohlins springs — set at an angle of 25 degrees controls steering. This delivers a 56.5-inch wheelbase with 3.9 inches of trail, resulting in a 52/48 percent distribution of the Irving Vincent’s 407 pound dry weight.
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