These are the known mechanical and performance specifications for your 2008 Enfield Thunderbird 350.
Basic Specs

Engine
Displacement346.00 ccm (21.11 cubic inches)
Type
DetailsSingle cylinder, four-stroke
Max RPM
Compression7.3:1
Bore/Stroke70.0 x 90.0 mm (2.8 x 3.5 inches)
Valves/Cylinder
FuelingCarburettor. CV
IgnitionDigital TCI
Exhaust
LubricationDry sump
CoolingAir
Performance
Horespower18.00 HP (13.1 kW)
Torque27.50 Nm (2.8 kgf-m or 20.3 ft.lbs)
Top Speed110.0 km/h (68.4 mph)
Fuel Economy & Polution
Fuel Consumption
Fuel Capacity14.50 litres (3.83 gallons)
Emissions
Chassis
Frame Type
Rake
Trail
Front SuspensionTelescopic fork
Front Travel
Rear SuspensionSwing arm
Rear Travel
Seat
Seat Height
Alt. Seat Height
Total Height1,080 mm (42.5 inches)
Total Length2,120 mm (83.5 inches)
Total Width750 mm (29.5 inches)
Ground Clearance140 mm (5.5 inches)
Wheelbase1,370 mm (53.9 inches)
Dry Weight163.0 kg (359.4 pounds)
Wet Weight
Wheels & Brakes
Front Tire/Tyre3.25-19
Rear Tire/Tyre3.50-19
Front BrakesExpanding brake (drum brake)
Front Brake Diameter178 mm (7.0 inches)
Rear BrakesExpanding brake (drum brake)
Rear Brake Diameter152 mm (6.0 inches)
Wheels
Comments
Optional electric starter and front disk brake. Royal Enfield is made in India.