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2013 / 11


For 4 stroke engine, piston up and down finish one cycle.

And now talk about the relationship between crank and the engine power (HP).

When use the extended stroke crank, it sure to up displacement (c.c.), but the turning speed of the crank will be slow than original crank and will influence HP.

It mean the big extended crank will run slow to finish a cycle.

(The speed to finish a cycle: 8000 crank > 3000 crank)

Take G5 and Cygnus products for example:

1. The same G5 crank (stroke 54.5), the bigger cylinder, the bigger HP.

G5 61mm cylinder+54.5 crank = 159cc

G5 63mm cylinder+54.5 crank = 169cc

2. Up to 169cc

G5 63mm cylinder+54.5 crank = 169cc

Cygnus 61mm cylinder+57.9 crank =169cc

If G5 want to compare with Cygnus 169cc, it needs to use 63mm cylinder.

The stroke of G5 crank is short, it need the cylinder to make up for.

But if about the HP, G5 matched kit will be powerful than Cygnus, since the stroke is short.