Endurance test KTM 620 LC 4

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Endurance test KTM 620 LC 4

Kick and fit

The premature end of the endurance test is not a consequence of increased material wear? the KTM is fit for further expeditions, only the drivers are tired.

The silent, motionless and completely withered mummy face of the sandy sea Itan Aubari in the Libyan part of the Sahara takes on frightening features from one minute to another. The sand dunes glow in the midday heat. The one-hour break in the poor shade of a meager tamarisk bush did not fully restore physical resources. And what has already been indelibly stored in the head as a fixed idea, proves itself again: the KTM does not start.
The search for the cause of the starting difficulties follows the same track for the umpteenth time: Checking the key position in the ignition lock, which with its four positions causes confusion and is also difficult to reach with gloves. The imaginary checklist also includes the position of the kill switch and that of the miniature petrol tap, the position of which cannot be felt at all.
The success of the actual starting procedure – the courageous step on the kick starter lever, which is as long as it is high – depends essentially on the constitution of the stressed approach: If he does not step through to the stop, the energy is ineffective in the crankcase. But it can also happen that the kickback pushes the carburettor backwards on its socket or – as happened at mileage 35995 – the air filter dies from fire as a result of the kicking back flame front.
The sympathy for the weight-saving starter system disappears completely when the kickstarter is no longer pulled back into its starting position by the return spring, but instead gets stuck on the footrest bracket.
In view of the many hundreds of unsuccessful attempts to start over the course of the two-year test period, it is not surprising that the logbook of the KTM long-term test shows a noticeably high number of idle times. Their acceptance suffered from their moodiness: does the engine start or not? If he does not, the driver tends to look for the reason for his failure with himself first and is frustrated. In this regard, KTM expresses itself as follows: “The rider’s routine has a great influence on the starting behavior.” In other words: If you don’t get it, it’s your own fault.
The fact is, however, that the single-cylinder reacts extremely sensitively to changes in its technical environment: the Dellorto carburettor in particular proves to be a sensitive component with a high proportion of the error rate. The high swimmer level, which KTM outed as a possible cause of the starting difficulties, may have been one of the reasons for the starting problem.
Because the starting behavior never followed a logic, the tenor of the comments in the logbook changed as quickly as the weather in April, namely every hour: Shortly after the entry “You sink them in the Neckar”, it says: “Jump on the first step ! ??
The unpleasant quality of reluctantly releasing idle despite a sensitive search and – if this is successful – not even showing it reliably with the green neutral display, has consistently cost people sympathy. Likewise, the peculiarity of suddenly dying off at civil engine speeds while idling. Because of the relatively low flywheel mass, the powerful four-valve engine shows such a gruff character in the lower speed range that there is no talk of well-groomed manners – despite the balancer shaft.
The big jump between the first two gears as well as the standard secondary gear ratio (16/40) increased the frustration in city traffic, especially off-road to such an extent that the LC 4 had a shorter gear ratio (15/45) at 900 km. got donated.
The KTM and its riders would have been spared various police checks and a few compulsory stops when it got dark, had the motorcycle not worn out lightbulbs in an almost outrageous way. The vibrations, which are barely bearable for humans thanks to the balance shaft, are apparently associated with frequencies that have a deadly effect on the sensitive material of the already sparse lighting equipment.
That it is by no means enjoyable to do service work with the qualitatively mediocre on-board tool kit is only mentioned in passing. For example, candles cannot be changed without bloody knuckles.
However, the KTM 620 LC 4 proves its constructive origin from the hardcore enduro camp not only through the constant ailments in everyday use, but also through highly professional properties: it has repeatedly proven its suitability as an expedition device in the toughest terrain in weeks of travel. The stamina of your chassis and drive components must be given the utmost respect.
The fact that the return spring of the kick starter shaft broke, the Bowden cable of the decompression lever tore and the high main stand showed signs of a fatigue break towards the end of the endurance test should not come as a surprise in view of the many gymnastics exercises that had to be carried out on the KTM with the sole aim of physical fitness.
Apart from the regular inspections every 10,000 kilometers, the list of the necessary spare parts and the unscheduled workshop visits remains manageable. The first damper overhaul was only necessary when the odometer reading was 28911, despite tough off-road use. Only one spoke suffered a fatigue fracture, and the fork seals only had to be replaced twice due to leaks. The increasingly jerky and poorly separating clutch was given new friction discs at 34640 kilometers.
The decision to look into the bowels of the LC 4 after 26 months and 40,000 instead of the usual 50,000 kilometers of endurance test is not just a consequence of the love-hate relationship that has developed between man and machine. It is also a concession to the varied and exhausting life between sandy Sahara, stony Pyrenees and agonizing stop-and-go traffic. The fact is: the engine made unusual mechanical noises for the first time after 35,000 kilometers. However, these noises had no disturbing influence on the willingness of the Austrian stew to perform. The final measurement at a mileage of 40,000 even certifies a fuller performance curve with the same peak performance.
The dismantling of the single after the premature end of the long-distance test revealed the possible causes: a worn-in timing chain rail and a damaged needle cage on the lower connecting rod bearing. Otherwise, the KTM 620 LC 4 is technically and visually in perfect condition – ready for the next circumnavigation of the world.
D.he last written document in the logbook deals – how could it be otherwise – again with the topic of starting: The sentence “One step is enough” can be understood as a conciliatory happy ending to the KTM long-distance test. For all those who prefer not to make such promises, I should say as a consolation: The KTM LC 4 is now also available with an electric starter and will soon also be available as a 640 with more displacement.

KTM takes a stand…

…Regarding the starting difficulties and the unstable idling: The driver’s routine has a very large influence on the starting behavior. The starting difficulties of some test drivers are probably partly due to this. Nevertheless, we suspect one of the causes is that the float level of the Dellorto carburetor is too high. That the starting problems were resolved after correct setting suggests … on the leaky fuel filler cap: This is a known problem when the rubber seal is badly seated. The rubber can be repositioned correctly by hand, then the tank cap is tight again. From the 1998 model onwards, the problem has been solved by a lockable fuel filler cap …. on the gear ratio step between first and second gear: This is known and has been changed from the 1997 model onwards. From 4:24 pm (2nd gear) to 3:24 pm … to the defective manual decompressor cables: an actually unknown problem. The rope quality is checked. It could also be due to the wrong setting of the rope … on the defective speedometer cable: The service life could be extended significantly by correcting the speedometer position. When changing tires, the lower union nut is loosened and often no longer tightened correctly. This then leads to the fact that the speedometer cable can come loose and also fall off completely … to the clutch chattering: the problem is known. From model year 1998 an O-ring version will be installed (service notification). The clutch picking has largely disappeared. In addition, from the 1998 model, improved friction linings are also used … for commuting at higher speeds: The chassis is primarily designed for the enduro sector and of course a compromise between handiness and straight-line stability. The oscillation mainly occurs when the air pressure not correct or if the choice of tires is not adapted to road use. Recommended tires are Metzeler Enduro 3, Metzeler Enduro 4, Michelin T63, Michelin T66. With these tires and with the correct air pressure, there is no longer any commuting.

Reading experiences

Current mileage of my 1994 competition: 17,000, more than half of which in the field. Problems so far: The clutch burned up during a desert tour, and the radiator boiling over had no long-term effects on the durability of the engine. What I like: – stable chassis with excellent suspension elements; – unbelievably lively engine and great performance. What I don’t like: – Kickstarter is annoying, even if the engine starts immediately; – Hell’s vibrator (without balance shaft) at more than 110 km / h. It should be noted that the KTM is not easy to drive off-road for beginners. Eduard Kraus, I drive one KTM LC4 EGS with first registration March 1995. Except for the shortened gear ratio (15/40) I drive in the original condition. A five-star topcase for Givi suitcases is discreetly mounted on the luggage rack. In terms of tires, the LC 4 is equipped with Pirelli MT 21, which offers a good compromise between roadworthiness, good off-road traction and reasonable durability. At 800 km the swimmer stuck, with a bit of filing the problem was solved forever. Otherwise I had no problems. Even sinking it in a ford up to the tank put my KTM away without complaint. Kick it a couple of times and it was running again. The LC 4 is fast, easy to handle and has a long range thanks to the 20 liter tank (consumption on average 5.7 liters / 100 km). The vibrations can be felt permanently, but are only annoying at speeds over 120 km / h. The robustness and ability of the LC 4 to suffer is exemplary. There are no broken fittings or gear levers. Some Japanese Enduro would have died long ago (I had three Japanese before, so I know what I’m talking about). Roland notes

Status

Engine: All four valves with light deposits, but tight fit. Valve seats slightly hammered in on the inlet side. Bone shaft without wear due to the roller rocker arms and in very good condition. All valve guides within the installation tolerance. Piston dimensionally accurate, with perfect running pattern and low oil carbon bearings. Upper piston ring with too large joint clearance (must be replaced). There are slight grooves in the coating of the cylinder liner, but wear is within the installation tolerance. Control chain rail is slightly worn. The copper coating of the needle cage on the lower connecting rod eye is worn, resulting in slight scoring in the connecting rod bearing bore. Connecting rods including bearings and bolts must be replaced. Power transmission: Primary drive, clutch discs and clutch basket in very good condition and with little wear. Gear wheels with no visible wear, no pitting, a shift fork with slight marks on the side. The return spring of the kick starter shaft is broken and needs to be replaced. Chassis and equipment: Frame paint mostly in very good condition. Paint peeling off only in the area of ​​the footrests and the frame joists. The paintwork of the rear frame in the area of ​​the bench seat has been worn away. The very well-sealed bearing points of the swing arm and reversing lever are free of play and without corrosion. Front silencer corroded at the weld seams, remaining stainless steel exhaust system in good condition, bearing points of brake and clutch lever worn out, electrical plug connections without traces of corrosion and with a tight fit.

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