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TECHNICAL SPECIFICATIONS – ENGINE
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Engine oil
Only use fully synthetic engine oils that meet the JASO
MA quality requirements (see information on the can).
KTM recommends Motorex Power Synt 4T in the 10W/50
viscosity (for temperatures over 0°C, 32°F) or 5W/40
(for temperatures under 0°C, 32°F).
0°C
32°F
10W/50
5W/40
JASO T903 MA
TEMPERATUR
ENGINE
640 DUKE II
Design
Liquid-cooled single cylinder 4-stroke engine with balancer shaft and electric starter
Displacement
625 ccm
Bore / Stroke
101 / 78 mm
Ratio
11,7 : 1
Fuel
unleaded premium gasoline with a least RON 95 (USA = Premium RON 91)
Valve timing
4 valves over rocker arm and 1 overhead camshaft, camshaft drive through single chain
Camshaft
249/1
Valve diameter
Intake: 36 mm, Exhaust: 32 mm
Valve clearence cold
0.12 - 0.15 mm
Crank shaft bearing
2 cylinder roller bearing
Connecting rod bearing
needle bearing
Top end bearing
bronze bushing
Piston
forged aluminium alloy
Piston rings
1 compression ring, 1 taper face ring, 1 oil scraper ring
Engine lubrication
2 Eaton-Oilpumps
Engine oil
see table #
Quantity of engine oil
2.1 liters including frame
Primary ratio
straight geared spur wheels 31 : 79 teeth
Clutch
multi-disc clutch in oil bath
Transmission
5-speed claw shifted
Gear ratio
1st 14:35
2nd 15:24
3rd 18:21
4th 20:19
5th 22:18
Ignition system
contactless DC- CDI ignition with digital advanced system type KOKUSAN
Ignition timing
adjustment to max. 38° BTDC at 6000 rpm
Generator
12V 200W
Spark plug
NGK DCPR 8 E
Spark plug gap
0.9 mm
Cooling system
liquid cooled, permanent rotation of cooling liquid through mechanically driven water pump
Cooling liquid
1 liter, 50% antifreeze, 50% water, at least –25° C (–13° F)
Starting equipment
electric starter, kick starter
#
BASIC CARBURETOR SETTING
640 DUKE II
Carburetor
BST40-273
Main jet
165
Needle jet
X-6 689
Idling jet
45
Jet needle
6G5
Needle position from top
3rd
Mixture adjusting screw open
2.25
