21 TECHNICAL DATA 173
21.1 Engine
Design 1-cylinder 4-stroke engine, water-cooled
Displacement 690 cm³ (42.11 cu in)
Stroke 84.5 mm (3.327 in)
Bore 102 mm (4.02 in)
Compression ratio 12.5:1
Control OHC, 4 valves controlled via rocker arm, chain drive
Valve diameter, intake 40 mm (1.57 in)
Valve diameter, exhaust 34 mm (1.34 in)
Valve play, cold 0.07… 0.13 mm (0.0028… 0.0051 in)
Crankshaft bearing 2 roller bearings
Conrod bearing Needle bearing
Piston pin bearing Piston pin with DLC coating
Pistons Forged light alloy
Piston rings 1 L-ring, 1 tapered compression piston ring, 1 oil scraper ring
Engine lubrication Semi-dry sump lubrication with two rotor pumps
Primary transmission 36:79
Clutch APTC™ antihopping clutch in oil bath/hydraulically operated
Gearbox 6-gears, claw-shifted
Transmission ratio
1st gear 14:35
2nd gear 16:28
3rd gear 21:28
4th gear 21:23
5th gear 23:22
6th gear 23:20
Mixture preparation Electronic fuel injection
Ignition Contactless controlled fully electronic ignition with digital igni-
tion adjustment
Alternator 12 V, 224 W
Spark plug NGK LKAR 8AI - 9
Spark plug electrode gap 0.9 mm (0.035 in)
Cooling Water cooling, permanent circulation of coolant by water pump
Idle speed
Coolant temperature: ≥ 70 °C (≥ 158 °F) 1,550… 1,650 rpm
Starting aid Electric starter, automatic decompressor
21.2 Engine tolerance, wear limits
Camshafts - diameter, bearing pin
Next to exhaust cam ≥ 39.95 mm (≥ 1.5728 in)
Next to inlet cam ≥ 17.96 mm (≥ 0.7071 in)
Valve spring
Minimum length (without valve spring cap) 42.3 mm (1.665 in)
Valve spring cap - thickness 2.4… 2.5 mm (0.094… 0.098 in)
Valve - valve stem diameter
Exhaust ≥ 5.93 mm (≥ 0.2335 in)
Intake ≥ 5.93 mm (≥ 0.2335 in)
Valve guide - diameter
New condition 6.004… 6.016 mm (0.23638… 0.23685 in)
Wear limit 6.050 mm (0.23819 in)
Valve - sealing seat width
Intake 1.60 mm (0.063 in)
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