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| | | EICMA: APRILIA MXV 450 |  Written: 15/11/2006 : 15:30. Read 33800 times (18/day). | The 45.2 engine has already accumulated titles and victories in enduro and supermotard racing. Now the same engine has become the heart of the new MXV, the first motocross bike in the world to be powered by a twin cylinder engine.
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ENGINE
In this dedicated motocross version, the engine maintains the unique configuration that has distinguished it from the start. The V angle remains 77°, and the cylinders with wet liners remain integrated in the crankcase.
The engine’s light weight is the result of radical choices in materials. The valves are in titanium, the crankcase in aluminium silicon alloy, and all covers are in magnesium. Everything about the engine is designed for minimum weight in conjunction with maximum strength and reliability.
The 45.2 engine is extremely civilised and silent running even in this motocross version, and complies easily with FIM rules for noise emissions (94 dB threshold). Just as its homologated sister machines, the MXV affords easy access for maintenance (plugs, oil filter, air filter), and boasts extended maintenance intervals, far above the average.
The engine has a dry sump lubrication system but on the MXV the oil tank is actually integrated inside the crankcase to eliminate unnecessary oil pipes and reduce weight even further.
The starter motor has been eliminated for the same reason. Starting is by kick-start only in order to minimise weight.
The sophisticated electronic engine management system also introduces a number of motocross firsts. The Dell’Orto fuel injection system is managed by a programmable ECU with mapping optimised for motocross use.
The radiator no longer comes in two sections but is a single central unit, reducing weight even further by eliminating unnecessary connecting pipes and hoses. Radiator capacity has also been increased to improve engine efficiency.
The salient specifications of the 45.2 engine on the new MXV:
- Electronic fuel injection.
- Dry sump lubrication with the oil tank integrated inside the crankcase. Separate lubrication for gearbox and engine ensures that the engine oil is not contaminated by clutch plate particles, and remains fully efficient for far longer.
- Single overhead cam, titanium valves.
- Single-piece crankshaft.
- Cylinders integrated in crankcase, wet liners.
- Single radiator.
CHASSIS
Not only have the dimensions of the perimeter frame have been optimised for motocross use, but the entire frame has been developed to complement the engine. Its design is unique among motocross frames. A tubular steel trellis is interference fitted to pressed aluminium side plates to form an extremely rigid structure. The engine also forms an integral part of the chassis, acting as a load-bearing element.
The variable section aluminium swingarm is far more than just an element of style, this is the most rigid swingarm on any motorcycle of this type. Rising rate linkages operate a racing monoshock calibrated specifically for motocross.
The Marzocchi upside down fork has 50 mm stanchions and is also calibrated for motocross. The fork is fully adjustable.
BRAKES
The MXV is equipped with Magura calipers and super-lightweight wavy discs (270 mm at the front). 
Aprilia MXV – Technical specifications
Engine:77° V twin four stroke. Liquid cooled. Single overhead cam with rocker operated exhaust valves, chain timing drive, 4 valve heads, titanium valves.
Fuel: Lead-free petrol.
Bore x stroke: 76 x 49.5 mm.
Total displacement: 449 cc.
Compression ratio: 12.5:1.
Fuel system: Integrated engine management system controlling ignition and fuel injection.
Throttle body: 38 mm.
Ignition: Electronic.
Starting: Kick-start.
Alternator: 220 W.
Lubricatio: Dry sump with oil tank integrated inside engine. Separate gearbox lubrication.
Gearbox: 5 speed. Motocross gear ratios:
1st 14/29
2nd 14/25
3rd 15/23
4th 18/24
5th 21/25
Clutch: Multi-plate in oil bath, cable operated.
Primary drive: Spur gears. Transmission ratio: 23/65.
Final drive: Chain. Transmission ratio: 14/49.
Frame: Steel perimeter frame with alloy members.
Front suspension: Ø 50 mm upside down hydraulic fork, double adjustment.
Rear suspension: Box section aluminium swingarm with cast body. Hydraulic monoshock with compression and rebound adjustment.
Brakes:
Front: Ø 270 mm stainless steel disc with floating caliper.
Rear: Ø 240 mm stainless steel disc with floating caliper.
Wheels: Light alloy.
Front: 1.60 x 21”
Rear: 2.15 x 19”
Tyres
Front: 80/100 x 21”
Rear: 110/90 x 19”
Dimensions
Overall length: 2,232 mm
Overall width: 800 mm
Ground clearance: 396 mm
Seat height: 996 mm
Wheelbase: 1,505 mm
Fuel tank:
Capacity 7.8 litres
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