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KTM 500 K4
Road Test Which Bike 1982
KTM have made a name for themselves in the large capacity bike field for their tough and powerful racers. But up till now their machines have been exclusively two-stroke. The introduction of a 500cc four-stroke is, therefore a bit of an unknown venture for them. It proved an unknown venture for this tester too.
The KTM's motor is made by
Rotax, and can also be found in SWMs and Can Am/ Armstrong. This particular
lump is 504cc with an 89 x 81mm bore and stroke, but there are 493cc and
562cc versions. It uses a four-valve head with the single cam belt driven
off the left side of the crank. The Nippondenso capacitor discharge ignition
comes off the other side. A 34mm Bing carb supplies the juice. Lubrication
is dry sump with oil in the frame and a double-trochoid pump is used for
circulation. Primary gears and a wet clutch take the power to the five-speed
Dave and Tim were working well together. I was admiring the sun dancing on the summer bracken, thinking that it was days like this which make life worthwhile, when I realised the bloody racket in the background was something I hadn't heard since the bad old days when people like Arthur Browning and Vic Eastwood used to be on telly every Saturday afternoon. Some of the reason for this noise was the nonstandard silencer fitted to the bike. The original item was an enormous steel contraption which wouldn't have been out of place on a Japanese trail bike. Apart from being a weight penalty it didn't do too much for the performance either.
Starting the KTM is rather like the old XT500 Yamaha. There's a window in the cam drive belt cover and you can turn the engine over with the aid of a pressor till the white spot appears and then hoof it over. It doesn't always work but you've got a better chance the harder you kick. As I was trying to kick it over on a somewhat off-camber bit of ground with little success, I decided to aim the bike down the hill and try a bump start. The rear wheel locked in second and third and by the time I'd found fourth I'd run out of hill. By this time I was feeling a bit of a prat. I eventually got going with the help of Dave's size 10 Alpine Star.
So there I was in this stream bed with nowhere to go on a bike I'd never ridden before. Maybe it wasn't going to be one of those days that make life worthwhile after all. Anyway, I stuffed it into first, eased out the clutch, stood on the pegs and started to pick my way up the hill to try and rejoin the course. First gear runs out of steam so it's into second. Too much throttle produces monster wheelspin in these conditions so I back off, toq much, and the bugger stalls. I am now in danger of suffering a serious loss of credibility, not to mention falling off the bike which is leaning at a crazy angle away from me. Bike and rider reach the bottom of the hill once more, a few feet apart. It's time to get violent. The engine starts as I try to snap the kick start shaft in two. Not wanting to be caught out again, I stab it into second straight off and dump the clutch. Wheelspin halfway up the hill, grab third and phew! made it. At the top of the hill I give Dave a look signifying that I've walked out of the house without my trousers and he says; "Funny that, Andy Roberton came up here last week and he couldn't get round either." As he is the current leader of the British Enduro Championship, that made me feel a lot better.
We move on to a different piece of ground where 1 can get some feel of the bike. Race up a few tracks and get a bit sideways. The power on the KTM is much more basic than anything you'll find in Japanese motors — even though it's fitted with a single balance shaft, you can still feel every power stroke. It comes on very strong at the bottom of the rev range, goes a bit flat mid-range then comes back in till the motor revs out. The top-end power makes this motor different: most big singles run out of pulling power well before they run out of revs. Like most four strokes, the KTM motor doesn't like sudden big handfuls of gas — it will either do nothing or cough severely and if the revs drop too low it will stall without warning. Apart from these points the motor will do anything asked of it. The front won't lift very easily on its own so a certain amount of pilot muscle has to be employed. This is particularly noticeable on downhills which can turn into a helter skelter run with the front wheel bouncing off everything.
For the first time, we've come across a disc brake on a proper dirt bike and I must say it's impressive. It's very strong but never caught me out. The single-piston Brembo caliper works on what appears to be a stainless steel disc; anyway, it isn't prone to rust. It is quite possible to come to a stop on wet grass using the front brake only, without falling off. This bike takes a long time to get used to, particularly if you're more familiar with two strokes. It took me about half a day. Different power characteristics need different techniques. The bike is very predictable on dry or loose going but I never never felt in control of the front end in wet conditions. The front end uses a 38mm Marzocchi fork which some might think on the petite side but there wasn't any noticeable flex. The back employs KTM's irreproachable single-shock Pro-lever set up and, even though it was set soft, didn't cause any problems. It gets the grip dwon too - on fast climbs with the rider's weight forward the rear wheel can be left to its own devices, which ensures continuous traction.
A lunchtime break at the local boozer gave me a chance to try the bike's road performance. This was an opportunity to appreciate the true meaning of tractability: top gear will pull cleanly from 15mph through to a maximum in excess of 95mph (according to the speedo in Dave's Cortina — the one on the bike runs out at 65.) At high speeds the bars tingle some, but the motor feels sweet enough and it handles. Also at these speeds the disc brake gives you the confident edge. Gear shifting is very smooth in any direction, the only criticism being the over large gap between first and second.
Now comes the crunch. If you're interested in this type of tackle for competition use, you're going to have to part with 1899 greenies. If you want the ultimate poser's trail bike it's going to be £2079 with taxes paid. But at least you can be assured of a certain amount of exclusivity for your money. There won't be many around.
Source Which Bike 1982