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How much can I mill off the base of my cylinder

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How much can I mill off the base of my cylinder without having to run high octane just curious like .010 or .020 thous I know if you mill .030 off it'll detonate like crazy if you don't run race gas my bikes an 05 cr250

Edited by 2005cr250r

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How much can I mill off the base of my cylinder without having to run high octane just curious like .010 or .020 thous I know if you mill .030 off it'll detonate like crazy if you don't run race gas my bikes an 05 cr250

 

You can mill .030", and still run pump gas, if you enlarge the volume of the head +/-2.7cc to lower the compression.

 

The stock engine is borderline on pump gas so if you mill any amount off the base, good gas will be required unless you do head work.

Edited by CamP

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You can mill .030", and still run pump gas, if you enlarge the volume of the head +/-2.7cc to lower the compression.

The stock engine is borderline on pump gas so if you mill any amount off the base, good gas will be required unless you do head work.

Did you notice a noticeable loss in top end after you milled .030 off the base?

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No, he says he did not in other threads. I think I read somewhere that the exhaust port height was excessive already either on the 02-04 or the 05-07's I don't remember which. If the exhaust port is excessively high as it is, then you won't notice top end loss from lowering the cylinder.  

 

Did you notice a noticeable loss in top end after you milled .030 off the base?

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No, he says he did not in other threads. I think I read somewhere that the exhaust port height was excessive already either on the 02-04 or the 05-07's I don't remember which. If the exhaust port is excessively high as it is, then you won't notice top end loss from lowering the cylinder.

thanks I've read somewhere about that too but wasn't quite sure

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So by increasing head volume is that reffering to a port job. If left the squish stock and ported the head and took. 20 off the base of the cylinder would I get a low end power increase and still run pump gas?

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So by increasing head volume is that reffering to a port job. If left the squish stock and ported the head and took. 20 off the base of the cylinder would I get a low end power increase and still run pump gas?

2 stroke heads don't have ports

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Thats strange the numerous threads in this site about head modification and port work...? What is it you call the intake and exhaust ports on the cylinder? Also adjusting port timing? Maybe im calling it the wrong thing?

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Thats strange the numerous threads in this site about head modification and port work...? What is it you call the intake and exhaust ports on the cylinder? Also adjusting port timing? Maybe im calling it the wrong thing?

 

On 2 strokes you port the transfer chambers in the cylinder/jug. Not sure if there actually called transfer chambers, i'm thinking of the transfer port. But either way, thats where you do port work. You can modify the head by changing the squish band.

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Send the cylinder and head to Eric Gorr, he will mill .030 off the base of the cylinder and machine your head for pump gas or race gas whichever is your preference for $100.  My 250 had no loss in top end and it completely changes the power delivery of the bike.  Wen't from being unridable in stock form to being awesome. 

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