Cylinder or head mod?

[Matt Fisher]

I've decided to either have the base of my cylinder decked, or have the material taken out of the head; 03 CR250. Only pump gas is going to be run, btw.

My first priority is to get the squish gap correct, it's too big with all the correct gaskets installed, or even with the thinnest gaskets available.

Second priority is to get a bit more bottom end power out of the bike, without killing the top end pull.

So decking the cylinder seems like the logical solution, as the lowered ports should get me what I want. What I don't know is at what point do I end up doing more harm than good, or when it kills the top end power. How do I go about making sure that I'm not removing to much material (blocking ports or something else)?

 

[griffbones]

This sounds like excellent questions for Eric Gorr.

 

[Matt Fisher]

Sounds good to me. "Paging Eric Gorr. Eric Gorr to the white courtesy telephone please."

While all of life's questions are being answered (ok, just most of them), what kind of base gasket is preferred- the standard .020 paper ones, or the .010 stainless ones used on the 05+ Cr250's?

 

[helio lucas]

you could end with too much compression and size your engine...
i would do that in two or three times... little each time ... if you go too far simply put a thicker gasket...
if you want to do-it-yourself there are no magic formula or rules... only experience will tell you what´s better...

 

[tcuda499]

From what I have heard,learned here on DRN the newer cr's need to run premium fuel in stock form. If any of your mods will increase compresion you might have to use race fuel or at least mix 50/50. i'm interested to find out also.

 

[Matt Fisher]

I ended up running the base gasket from a 05+ CR250, they're only .010" thick. This brought my squish down, but I don't seem to need any race fuel. Bike runs good!