When they call it n even firing engine, they mean the power pulses happen evenly. As opposed to a harlet v twin which is extremely uneven firing. Its meant to balance the motor, and provide a smooth , even flow of power. They dont fire at the same time, they are 360 degrees apart. And as you know, a 4 stroke cycle lasts for 720 degrees.( two complete rotations of the crank)
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Thanks.....that makes sence now.

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...but polaris even said once it was a very low-tech design engine,
so i can't imagine to put all the money on that one.
must be to pass epa emissions with the less money tough...

 

I wouldn't call the motor too low tech. It does only use 2 valves per cylinder, but that helps it have that great low end torque. The compression is on the more mild side, but that keeps temps down and engine longevity up. It uses push rods and that aspect is a bit old fashioned. The plus side of the pushrods is that they are operated by hydraulic lifters... NO MAINTENANCE... no adjusting valves!!! For a utility quad I think they designed the engine right. If they wanted to put this in a more sporty chassis, I might agree that it is a bit low tech for it.

 

Many twins use a similar firing system, a single ignition controller for 2 cylinders whether it be electronic or mechanical points . My V-twin Harley has a single set of points and a single coil with dual plug wires. Both spark plugs always fire at the same time, but one cylinder is alwasy on the exhaust stroke when the opposite one fires on the power stroke. The crankshaft configuration is what is unique about the liberty engine, both pistons travel side by side and fire 360 degrees apart.

 

They have the twin because you produce more power with two cylinders firing as said above, as apposed to one large cylinder at which the fire can not cover the entire piston in time during the stroke to create power.

 

ds650-1 large cylinder, 2 plugs, [img]i/expressions/face-icon-small-tongue.gif[/img]

 

One of the huge benefits of this set up is you can use one carb and one exhuast and get the same power. This keeps it very simple and trouble free as well as costing less to build and maintain.

 

Not really. The 700 might only have 9.7:1, but the 600 has 10.2:1. That's pretty high to me.

 

YFZ is 11.9:1 and the YZF dirt bike is 12.5:1. Both use 5 valve, bucket/shim adjust, short stroke & super high revving. So, compared to most new cars, it's on the higher side, comapred to these 2 high tech motors, it's not that high.