Forgot part of my reply!!

With DOHC... consequently can run higher rpm... soooooo ... they stuff bigger cams in them from the get go becuase they can. Bigger cams mean lower power is going to go away.

It's a bummer that you couldn't come up with a way to vary the valve timing infinitely. Honda has a good start with the VTEC's in their cars but hasn't made it to quads that I'm aware of.

 

Closest thing I know of is the 'Dale ... the ignition timing varies through the RPM's and advance ... like how much advance there is at what RPM .... all in the effort to get that perfect spot for spark. Thought I'd throw that in for a partial answer to your inquiry.

 

I didnt read what everyone else said but here goes:
Dual cams allow for better placment of the valves. In other words your not limited with angle and placement by trying to make them all work on one cam. You can come up with a better flowing head if you use 2 cams. 5 valves vs 4 valves. My guess would be 5 can be better but only if you spend a whole lot of time and money on designing the head. Its probably not enough better than 4 to be worth it though.

 

There are so many plusses of DOHC that we could go on for weeks about all of them.

Thomez...you are absolutely correct but the Dale is not exclusive to the ignition advance. To my knowledge... all bikes have ignition advance... very similar to a car. It's all controlled by the CDI. Basically... the faster you turn the engine, the sooner you have to light off the fuel to get it started burning soon enough to get the power out of it. If my knowledge of the Dale is correct though.. you can adjust it to your particular setup or riding style.

What I was talking about was variable VALVE timing... completely different things. Basically the theory is to have a small "torque cam" at the bottom, a "mid range cam" in the middle, and a "hi rev cam" at the top...all dependant on engine rpm. Almost exactly how a distributor on an older car advances the ignition timing using a calibrated set of weights... the faster it turns, the more advance it gets.

 

Ferrari was experitmenting with cam profiles that would throw the rocker arm clear of the cam at high revs for extra extra lift and duration. That would be sweet in a quad. Would have to constantly check the valve clearances though.

 

BlackWidow ... I agree. Do all of the bikes have CDI's? I was under the impression that just the newer fancy bikes did. I don't think something like ... my Wolv has anything of the sort. Not sure though, so correct me if I'm wrong.

The 'Dale is .... infinitely adjustable. You just need the right software and you can do anything you want with the maps. Change fuel flow, injector offset, timing advance ... at RPM intervals all the way up the powerband. It's pretty neat. Maybe a good comparison is it is like being able to make your own CDI instead of relying on an aftermarket company to make the best one for you. You can custom tune your CDI to your own mods ... pretty cool deal.

Don't expect VVT in a quad anytime ... too soon. Look how long it took to get EFI in there ... and nobody big has really followed up on that either.

 

Just look for the "little black box" that has several wires leading into it. That'll be your CDI. I couldn't give you specifics, but I've never seen a mechanical ignition advance on a bike.... therefore it must be electronic!

 

I reckon so ... I've just never looked for it. Maybe it was better I had never thought about it ... cause before you know it I'll be wanting an aftermarket one [img]i/expressions/face-icon-small-tongue.gif[/img]