My thanks to John Blackburn for forwarding pictures of both the 897 and 896 models together with some information.
The 897 was used for the Speedway circuits, whilst the 896 was a Longtrack machine, this particular machine being that of Czech P.Vandirek.
The Jawa 897 is a 4-valve, air cooled SOHC motor with a displacement of 493ccm. Both the Jawa 896 and 897 models have their rocker arms forked and provided with traversing wheels rolling on cams of a central camshaft.
Also, both models have oil supplied to the crankpin bearing and the camshaft compartment by a twin pump mounted on the valve gear cover. The splashing oil also lubricates other parts of the driver unit, namely the rocker arm's bushings, valve gear chain and main bearings of the crank mechanism. This lubricating system was changed with the arrival of the 898 model.
Longtrack machines are similar to those used in Grass Track in that they have two gears. The long Tracker has a special gear shift mechanism which the rider engages by pressing down on a lever located on the handlebars close to the Clutch lever.
Both machines had frames made from circular CR-MO tubes. The short trackers have a detachable rear section of frame carrying an unsprung rear wheel, whilst those for the long 1,000m tracks have a conventional rear swinging fork made of steel tubes, which is cushioned by two units consisting of an outer coil spring and a liquid, or gas liquid shock absorber.
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