Royal Enfield Classic 350 Service Manual download pdf (Page 11)

02-6

IGNITION TIMING :

Ignition timing is the timing in degrees of rotation

of crank shaft at which spark commences so that

the spark from the spark plug can ignite the

mixture in the combusion chamber at the end of

TDC during compression stroke.

If spark occurs earlier than specified ignition timing,

it is called “Advance” timing.

If spark occurs after the specified ignition timing,

it is called “Retard” timing.

IDLING SPEED :

It is the speed of the crankshaft (i.e. RPM) of the

engine when the throttle is in closed position.

Gear ratio :

The relative rotation between “Driven Gear” and

“Driving Gear” is known as the “Gear Ratio”. It is

determined by number of teeth on the respective

gears.

Gear Ratio =

No. of teeth of Driven Gear

No. of teeth of Driving Gear

In Fig. 1, the Gear ratio is 20 ¸ 10 = 2 : 1

In Fig. 2, the Gear ratio is 20 ¸ 20 = 1 : 1

Gear ratios multiply the engine torque to fulfil

various demands for pulling the vehicle like.

- More effort is required during initial move-

ment of the vehicle.

- More effort is required to climb an elevation.

- More effort is required while driving in muddy

or sandy surfaces etc.

FINAL DRIVE RATIO :

It is a relative rotation between the engine sprocket

and the sprocket on the rear wheel. Both the

sprockets are connected through drive chain.

Final drive ratio further multiplies the torque

available at the output shaft of the gear box.

Basic Terminology of IC Engines

TDC Position

Ignition Timing

1 2 ... 6 7 8 9 10 11 12 13 14 15 16 ... 228 229

No comments

Royal Enfield Classic 350 Service Manual Page 11