I just got told that ZZR250s (and GPXs) fire both cylinders at the same time! Hmm I would have thought this to be a bit silly as it would vibrate heaps, and would therefore need a counter-balance shaft...
Can anyone confirm or deny this???
I just got told that ZZR250s (and GPXs) fire both cylinders at the same time! Hmm I would have thought this to be a bit silly as it would vibrate heaps, and would therefore need a counter-balance shaft...
Can anyone confirm or deny this???
Yeah, it's called a 'Parallel Twin' I believe.
Has something to do with getting the torque of a single, but being able to rev like a twin.
But don't quote me on that. [)]
Check this site out. Parallel twin drag bikes
http://www.thefang.co.uk/parallel.htm
MarkC
Hmm I always thought the term parallel twin was given to an inline-2, regardless of the firing order... You've got TRXs and old brit bikes that are parallel twins but have 270 degree cranks... I could be wrong tho!
Yeah you're right m8 it does cover all inline twins.[:I][quote:Originally posted by J7-11
Hmm I always thought the term parallel twin was given to an inline-2, regardless of the firing order... You've got TRXs and old brit bikes that are parallel twins but have 270 degree cranks... I could be wrong tho!
I checked with another m8 and the ones that fire both cylinders at the same time have a 360 deg crank throw, but it doesn't actually fire both cylinders, just the plugs. It's basically the same as if you chopped cylinders 2&3 off a 4 cylinder motor.
The coils on the 4 fire pairs of plugs (1,4 2,3) at the same time, one piston is at the top of its compression stroke, and the other is at the top of it's exhausting stroke.
stroke 4 Cyl 2 Cyl 360 2 Cyl 270
stroke 1 fire 1 fire 1 fire 1
stroke 2 fire 2 no fire fire 2
stroke 3 fire 3 fire 2 no fire
stroke 4 fire 4 no fire no fire
The 360 deg throw gives a smoother power delivery, and 4's are even smoother.
MarkC
Yeah that's what I told the guy, that somewhere along the line someone has said 'ZZR250s fire both cylinders at the same time' which of course was in reference to the wasted spark thing, and someone took it literally and hence the confusion... will ask a mechanic mate just to be sure tho!
Cheers!
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