Hi all,

Does anyone know the differance between the fzr600r engine producing 90hp at 10500rpm with 12:1 compression ratio and the thundercat engine producing 105hp at 11500rpm with 12:1 compression ratio?
Could it be cams?

The compression was higher in the T'Cat and the rod + crank were made stronger to cope, or at least that's what I thought, but it's only about 2 bhp difference or (2%)

A stock thundercat with full race system will never make a true 105bhp. A good one will be 95-98bhp

Fzr600 low 90s.

Does anyone know the differance between the fzr600r engine producing 90hp at 10500rpm with 12:1 compression ratio and the thundercat engine producing 105hp at 11500rpm with 12:1 compression ratio?

Hi, as far as i'm aware if your talking about the earlier 3he FZR600, (pre 94) it's engine has a longer stroke and smaller bore than the 4jh/4tv FZR/YZF 600R. Apparently it makes more torque but less power (longer stroke can't rev as high). It's supposed to be nicer to ride with, but Yamaha had to change the spec in order to compete with the CBR600F's 100bhp (as no-one looks at torque figures only max power).

Apparently it is possible to build a 660 by mating the earlier crank with the later engine Something i considered myself, but it's not as straight forward as it sounds!