High Compression Pistons?

[jwick07]

My 450R is still falling all over its face from 3/4 to WFO, i changed the plugs, the jetting, the rev box, air filters, with lid with out lid, and still no big improvement in the problem. So im just going to have the motor torn down and rebuilt a littler sooner than I had planned. To the point my friend that is going to do the rebuild wants to put a 13:1 compression piston in like he did on his. But he has to run race fule all the time. I said 11:1. But I'm really sure what the gains are with the higher compression.

[Pappy]

id go atleast 12-1 with a good cam.

the compression really wakes up the R, especially if you ride an 06 compared to an 05:D

[jwick07]

Well crap! Papy I'm old school I guess. I role on a 2004. Bought it for myself as a college graduation present.

I have the HRC cam is that good enough, with ESR rev box, hmf slip on, k&N. What does the high compression piston do though to create the motor to wake up! and why 12:1 instead of 11:1 and can i still run 93 octane with the 12:1

[Pappy]

from what im told, you can squeek by with premium with a 12-1. id consult someone more mechanically schooled then me but thats what i will be running soon. the hrc cam and a 12-1 should work pretty good.

[tater_kamik]

you may be able to throw a little tolulene in your fuel to raise the octane if 93 isnt high enough... tolulene is also very cheap!

[wilkin250r]

Higher compression equals more power, plain and simple.

Now, it won't increase peak power all that much, maybe 2-3HP at the peak, but it REALLY wakes up the low-end and midrange. With a 13:1, I bet you see a full 5-7HP increase at 6000 rpm.

A high-rev cam that gives you an extra 10HP peak will generally lose at least 5hp in the low-end. Many race motors and packages combine a high-rev cam for peak HP, and high compression piston to regain everything lost on the low end.