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Classic Motorcycle Review - Posted 28th March 2008

Yamaha XS650 Road Racer

Richard Cheetham wanted to build a competitive classic racer out of a Yamaha XS2. But doesn’t everyone say they handle really badly...?

The idea to build an XS2 road-racer was born out of my experience of the type many years ago, when I modified an XS650 to use in the Ultimate Street Bike competition which began in the late 1980. That bike, a scruffy non-runner XS650B, was bought for £60 after haggling the seller down from his £100 asking price, and brought home on a trailer.

Classic leathers for classic racing? Yamaha XS2 Classic Racer

The engine was enlarged in the usual ways, and tuning carried out with very basic facilities, I remember doing some porting work using hand scrapers made from scrap files. Without access to a dyno, all tuning modifications were evaluated by running against the clock over the quarter mile, but the conclusion of this work was a bike capable of an 11.6 second standing quarter and 117 mph terminal speed. This performance was sufficient to win the 1990 four-stroke twin championship, and proved the engine had the potential to match any other two-valve twin, including the air-cooled Ducatis of the period.

Classic hair to match classic leathers? Yamaha XS2 Classic Racer

With this history in mind I was confident of extracting competitive horsepower from an XS2 engine. The only real problem was going to be the vibration at higher revs which is inherent in the 360-degree parallel twin engine design. As all motorcycle engineers are well aware, the 360-degree big twin is not the way to a fast, reliable or user-friendly motorcycle. The only saving grace of the design has been cheapness and ease of manufacture.

Classic British weather? Yamaha XS2 Classic Racer

I was not sure of the capability of the standard Yamaha chassis when compared to the Seeley, featherbed Norton, or Rickman Metisse which are the mainstay of the big twin class in classic racing today. Most contemporary road test reports on the early Yamaha twins (XS1/XS2) were quite scathing in their criticism of the bikes’ roadholding and steering. This nonsense has grown in authority with the passing of the years to become one of the great bar stool legends of our time. Phrases such as ‘bendy frame’, ‘twisting swinging arm’ and ‘hinge in the middle’ can be found in any guide to the model published to this day.

My own belief is that the legend originated in the motorcycle press, who were still firmly in the pockets of the British industry at the start of the 1970s. They did their bit to dampen sales of the model, which came in as a direct competitor to the big twins which were all that remained of the dying British industry.

Since most prospective customers could not be fooled into believing the Yamaha powerplant was not a great improvement over the British offerings which remained, the only criticism which could be levelled with impunity was of that intangible quality called handling and so the legend was born.

In fact the Yamaha chassis is handicapped by a serious lack of ground clearance, and this problem must be addressed if the machine is to be adapted for racing. The standard machine has the engine and lower frame rails slung very low relative to the headstock. This makes for a low centre of mass and good stability at modest speeds and so cannot be seen as a criticism unless the bike is to be taken out of the role it was designed for.

Classic British block-paving? Yamaha XS2 Classic Racer

The bike featured here has the standard XS2 frame with nothing added in the way of strengthening, So far it has not given any cause for concern, though I must admit to not having been spoiled by riding anything manufactured later than the early 1980s so maybe I’m just not that fussy.

The lack of ground clearance mentioned earlier was responsible for one accident on the track when I carelessly decked the engine out in the fast Honda curve at Pembrey. This incident causing a distressing amount of damage which I don’t want to repeat. As with any other bike of this age which is to be used for serious competition, good quality rear suspension units are needed. Mine were supplied by Ron Williams of Maxton suspension and they do a good job.

Classic Stuff on Now...

The frame finish is called smoke chrome and was done by Trevor Walshaw, proprietor of alloy wheel refurbishment company Metal Magic in Barnsley. Vapour blast cleaning of engine castings is also courtesy of Metal Magic. The fabulous paint job on the fuel tank, a Peter Keyte fabrication, was undertaken by Barnsley garage owner and classic racer, Ray Howarth. Wheel building is by former classic racer Dave Baxter, finish boring of cylinder liners by Neil Bland of Bland Precision Engineering, again a former racer himself. Specialist alloy welding was by Stan Plusa, technical college instructor in fabrication and welding processes. Electronics (a rev limiter system for PVL ignition) from David Hirst; cam profiling, by Phil Joy of Joy Engineering. Many of the performance parts for XS2/XS650 engines came from Dave Rayner of 650 XSories in Sydney, Australia.

Classic Japanese bike? Yamaha XS2 Classic Racer

I built two engines for use during a racing season. The first was a close copy of the 743cc 360-degree motor which I ran initially, but it incorporated a few detail improvements, including the Dave Hirst rev limiter system for the PVL ignition used on this motor.

Just.... classic Yamaha XS2 Classic Racer

The second engine was an 840cc unit with re-phased crank, (90-degree advance on the right hand crankpin). The objective was to reduce vibration and hopefully permit higher engine revs with less rider fatigue as a bonus. This engine used internal parts from Dave Rayner in Australia, and a digital ignition system by Pazon ignitions which incorporate a programmable rev limiter as standard.

The bike was campaigned to second place in the CRMC unlimited twin championship in 2005, and raced again in the 1300 twin cylinder CRMC class. That wouldn’t have been possible without my regular paddock spanner man and polisher Roger Senior, and my family who have supported me from the start of this venture.

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Go Racing

The Classic Racing Motorcycle Club organise classic races for bikes built between 1945 and 1986 at top circuits across the UK.

  • www.crmc.co.uk



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