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I posted this in reply to another thread to give an idea of how we are getting more power. I just thought starting a new thread so more people see this would be helpful. I'll add more later but right now it's getting late and I'm tired.

"They didn't do it because of emissions. I've been thinking about this tonight. By advancing the exhaust cam they widened the LSA or lobe separation angle and reduced valve overlap. Stock, the exhaust lobe is further from the intake lobe, which does broaden the powerband but reduces peak power and emissions.
Remember the 4 stroke model: Exhaust, intake, compression, power. Some guys might think the exhaust event comes right after the intake event. Contrare, it's the opposite. The exhaust stroke expells gases on the up stroke, the intake stroke draws in air on the down stroke. The compression stroke occurs on the up stroke and the power stroke is the result of the spark going off, igniting the mixture.

By retarding the exhaust cam you now get more overlap and exhaust scavaging when the intake event occurs. This is due to the intake valve is beginning to open when the exhaust is not fully closed. It takes a bit longer to build cylinder pressures like this and you get more emissions by forcing out more exhaust. The scavaging is because you've opened the intake valve, letting in more fresh air, forcing out nasty exhaust fumes. That is the main reason you get more power. Better cylinder filling once that exhaust valve gets closed. Duration and lift remain the same, the power is made from valve timing and scavaging created from overlap.


Note:
I have not drawn this out yet since I do not have these cam specs, and it's very late, so bear with me if I have made any errors."
 

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HEY THANSK FOR THE TIPS. I ALWAYS THOUGHT THEY DID IT TO SLOW THE BIKE DOWN. BECAUSE NOT TO DO THE EMISSIONS SINCE THE EMISSIONS ARE FROM THE PIPE RIGHT? DO YOU THINK I WILL GET A LOT OF POWER FROM THE CAMMOD?
 
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