BMW R 45 (1978-81) vs BMW R 39 (1925-27) vs Honda XR 125L (2006-08) vs Triumph 6T Thunderbird (1950-53)

Comparison technical specifications

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Make:	BMW	BMW	Honda	Triumph
Model:	R 45	R 39	XR 125L	6T Thunderbird
Years:	1978-81	1925-27	2006-08	1950-53
Engine:	Four stroke, two cylinder horizontally opposed Boxer, pushrod operated 2 valves per cylinder.	Four stroke, single cylinder vertical, OHV	Four stroke, single cylinder, OHC, 4 valve	Four stroke, vertical twin, OHV
Capacity:	453 cc / 27.6 cu in.	247 cc / 15.1 cu in.	124 cc / 7.6 cu-in	649 cc / 40.0 cu in
Compression Ratio:	9.2:1	6.0:1	9.5:1	8.5:1 (Export), 7.0:1 (UK)
Cooling System:	Air cooled	Air cooled	Air cooled	Air cooled
Induction:	2 x Bing V65 carburetors	1 x BMW Spezial ∅20 mm	22mm PD-type Carburettor piston-valve	1 x Amal Monobloc, 25 mm (1953: SU type MC2)
Ignition:	Bosch contact free electronic ignition	Bosch magneto generator type G 1.8V/15W	CDI	Lucas magneto
Starting:	Kick	Kick	Electric & kick	Kick
Max Power:	20 kW / 27 hp @ 7250 rpm	4.8 kW / 6.5 hp @ 4000 rpm	11.1 hp / 8,3 kW @ 8 500 rpm	25 kW / 34 hp @ 6500 rpm
Transmission:	5 Speed	3 Speed	5 Speed	4-Speed constant mesh
Final Drive:	Shaft	Shaft	Chain	Chain, 101 links
Front Suspension:	Telescopic hydraulic forks	Plate spring, 4 laminae	31mm Telescopic forks	Telescopic fork, hydraulic damping
Rear Suspension:	Long swinging arm with adjustable strut	Rigid, spring loaded saddle	Monoshock swingarm	Rigid, spring loaded saddle
Front Brakes:	2 x ∅260mm Disc, 2 piston caliper.	Internal shoe drum brake ∅150 mm / ∅5.90 in diameter	Single 240mm disc 2 piston caliper	SLS drum, 7 in
Rear Brakes:	Single ∅200mm drum	External shoe brake at the gearing on Cardan shaft	110 drum	SLS drum, 7 in
Fuel Capacity:	22 L / 5.8 US gal	10 liters / 2.6 US gal	12 Litres / 3.1 US gal	13.6 L / 3.6 US gal / 3.0 Imp gal (US), 18 L / 4.8 US gal / 4.0 Imp gal (UK and export)