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There is another reason that this is done to cranks. On four cylinders the power comes on all at once which effectively stretches the tire at the contact patch and then it takes a revolution off and lets everything catch up. This effect was mentioned already with the reduction of wheel hop. The other advantage is the pistons never come to a complete stop. In an engine with a 180 degree crank all four pistions come to a complete stop and then have to overcome friction to start moving again. In an engine with 90 degree crank throws while number one is stopping at the top No. 2 is reaching max speed downward, No.3 is reaching max speed upward, and No.4 is reaching a stop at the bottom. This way only half of the pistons are stopping at one time. There are other variations of the 90 degree crank too.

The biggest problem of this crank is that they need a balancer. You could prolly get by without one but who knows. I know the R1 and MotoGP bikes use them. Good luck if you decide to go through with it but for all the work, I would probably look into frame modifications and rear shock settings first. Not to mention better rear tires. Just a guess but I think you could tune wheel hop out enough that it shouldn't be a problem. These are old flexible frames not motoGP bikes. That being said. It'd be cool to do it just to do it.

It seems that the cost to benifit ratio would be two high to make this feasable on a KZ. On the other hand, have you heard the new R-1? It's hard to fathom that exhaust note coming from an inline four. That would be my favorite reason to do the change.

Cross plane crankshaft makes each piston 90 degrees apart from each other, instead of the customary 180 degrees between the two outboard cylinders and the two inboard ones. Each plug fires at 90 degrees of rotation, instead of 180. Four coils are needed. The result is raising a little the torque curve at the bottom, like a triple, at the expense of reducing a little the 'perfect' balance of the four.

It is practical for racing, where cost is not object, or for Yamaha on the R1 trying to best the triples, but trying to convert a KZ would be more expensive than buying a R1 in my opinion. It is not just the crank, it would also need an entire new ignition system with four coils.

Just a little note: a "crossplane" crank design and a "big-bang" firing order are not the same thing. The 90-degree firing-order of a crossplane crank as used by Yamaha puts the power-pulses closer together to get LESS shock to the rear tire all at once. A "big-bang" design makes a STRONGER power pulse, less-often, to give the tire more time to recover between power pulses. Ducati did this briefly, then went with a "normal" firing-order on its V4s because the "big-bang" engine was breaking cranks. It was "big-bang" because it fired two cylinders at a time, like two simultaneous twins, rather than running like a normal four-cylinder; the idea being that twins had always had a traction advantage on turns over fours, but were struggling against the performance of fours on the straights.

Could'nt you get most of the "Big Bang" effect by just replacing the cams with ones that are setup to have 1&4 fire at the same time and 2&3 fire at the same time? That would give you 2 cylinders firing, 180 degrees of crank rotation, 2 cylinders firing, 540 degrees of crank rotation before starting again. You wont even have to mod the ignition system or the crank.

Man, I'm getting cranked out. Whats that big bang? Cops! Run!

893cv wrote:

Could'nt you get most of the "Big Bang" effect by just replacing the cams with ones that are setup to have 1&4 fire at the same time and 2&3 fire at the same time? That would give you 2 cylinders firing, 180 degrees of crank rotation, 2 cylinders firing, 540 degrees of crank rotation before starting again. You wont even have to mod the ignition system or the crank.

You could, but then it would sound like a big CB350. It would probably vibrate like one too. I never did like the way those 180-deg honda twins sounded or felt. The 360 deg KZ twins sounded and felt much better. Too bad they were so heavy.

Pokes his head out of basement level crack house, white powder face, drum beats sounding in his ear, looking to the van across the street there in the drivers seat is the money he could have saved with an inline four. must have lost traction shortly after the big bang.