Kev, I have started to loose a bit of faith in these off the shelf high compression pistons, especially the domed type ones.

If I work out mathematically, based on Volumetric efficiency, then I should be seeing massive power gains when you add a high compression piston.

For example on my XT, making 44HP at 5800 RPM on my dyno with a 10:1 piston , VE works out to around 101% If I do the same calculations with an 11:1 piston and assume VE stays at 101%, then I should be gaining around 4.5HP@ 5800 RPM with just the piston.

Now, I have never seen that big a gain from just a piston alone. Maybe 1 or 2 HP, but that�s it.

I think the dome pistons mess with the combustion process and also the flow in some way and therefore don't see the big gains.

My next bunch of experiments will be to see if I can use the stock, flat top pistons, push up the compression and hopefully gain a bit more power than the dome pistons.

On the raptor, you have a massive potential to play around with and I hope the XT has the same potential. The raptor guys claim you can push the stock piston compression up by 1 to 2 points. That�s a lot.

I was also thinking of measuring the cam degrees and then just having the cam and "mounting plate' split, turned to the correct degrees and then pressed back into place.

Otherwise I will see if we can slot the cam sprocket or even have a new, adjustable cam sprocket made up.

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