long left behind

5 October 2001

Powerful workhorses fun image

long left behind

Bigger engines and more

user-friendly transmissions

are setting the trend in the

ATV market to provide more

work capacity from the

latest models.

Mike Williams reports

ATVs were developed in Japan as fun vehicles for the American leisure market. But their value as serious work machines for the farming and forestry industries was first recognised in the UK 20 years ago. Since then most of the design improvements have been aimed at increasing their workhorse potential.

The most obvious development has been a big increase in engine power for some of the top models. Current leader in the power race is Yamaha with its new Grizzly YFM 660FWA model, which employs a liquid-cooled, 660cc single-cylinder four-stroke petrol engine rated at an impressive 42hp.

But its a near thing. The 650cc unit fitted to Kawasakis KVF650 has an output power rated at 41hp. Kawasakis unusual choice of engine build is based on two cylinders arranged in a V formation. It also features a single overhead camshaft with four valves per cylinder. Like most of the big ATV engines, the Kawasaki is liquid-cooled using a front-mounted radiator.

Another of this years new arrivals in the high output sector of the market is the Honda TRX500 – the first liquid-cooled ATV engine Honda has produced. At 500cc it is also the largest engine so far, although a new 650cc model from Honda is due to be launched in the US next year and could be in UK showrooms in 2003.

The engine on the TRX500, like some other Honda ATVs, is mounted longitudinally in the frame, simplifying the power delivery. A new design feature is an "underhead" camshaft allowing a more compact engine design with the overall height reduced.

However, while the leading companies continue to offer ever more powerful engines, the towing capacity of the new generation of higher powered ATVs is increasing more slowly.

Kawasaki specifies a 567kg maximum towing weight for its 41hp 650 model and a 500kg limit for the 400cc models having a 28.6hp engine output. Permitted towing limits for both the 386cc and 401cc Yamaha models are also 500kg, increasing by 10% to 550kg for the new 660cc model. Hondas TRX500 also has a very modest 385kg towing limit.

Clearly, engine power is not the only consideration when towing limits are set – machine weight, brake capacity and handling characteristics are also factors.

But for many farmers recent improvements in transmissions are likely to receive greater appreciation than just bigger engines and the relatively small improvements in towing capacity they allow.

Automatic transmissions are available from most leading ATV manufacturers, but the Honda TRX500 has a new drive system which combines both hydrostatic and gear transmissions to provide automatic and manual options.

This new two-in-one transmission allows the operator to select the appropriate mode to suit the type of work the ATV is doing – the hydrostatic mode providing smooth, stepless speed adjustment and the manual setting a choice of five ratios, with finger-tip control.

The top Kawasaki model has an automatic drive system based on a constantly variable transmission (CVT) automatic drive system. This allows the operator to select two or four-wheel drive, while there is also a differential lock at the front plus four-wheel braking with discs at the front and wet multi-plate brakes at the rear.

Another of this years new arrivals is the Magnum 325 model in the Polaris range, designed with a 325cc engine to provide a smaller, cheaper alternative to the companys Magnum 500 model. The engine has a three-stage air/oil-cooling system with fan assistance, and the drive is automatic, using the familiar Polaris Variable Transmission (PVT).

Suzuki, back in business in the UK after a temporary absence, has also moved up the engine power league table and introduced a new easy-to-use transmission. The companys most recent introduction – the QuadMaster – is the most powerful Suzuki ATV so far. It has a 493cc engine plus the first automatic transmission to appear on a production ATV from Suzuki. &#42

Above:The Kawasaki 650 model is powered by a vee-twin engine with four valves a cylinder.

Left: the 500cc engine in the TRX500 is the biggest ATVengine Honda has produced and the first with liquid cooling.

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