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73 -75 CR250m cylinder porting

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expat

Post subject: 73 -75 CR250m cylinder porting

Posted: Thu Oct 20, 2005 8:29 pm

Joined: Thu Oct 20, 2005 8:14 pm
Posts: 66

Can anyone tell me why the bridged intake port has different heights?

Can I grind the lower height to match high port?

I have a fabricated reed valve assy to be fitted to my '75 CR250M and would like to know if any cylinder porting can be done to compliment the reed assy?

This cycle will be use for vintage MotoX racing only.

Thanks

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FirePig

Post subject:

Posted: Fri Oct 21, 2005 10:37 pm

Joined: Sun Jan 25, 2004 9:47 pm
Posts: 112
Location: Santa Rosa, CA

The lower port on the right side is there because the lower ring gap is there. It holds the ring in tight. If you do raise the port, which I inadvertently did, you can run just the top ring as I do or you can repin the ring gap pin on the piston.

My advice is to just leave it alone or raise it just a little bit but not enough to expose the ring gap.

_________________
Those who can make you believe absurdities can make you commit atrocities.

Loren Davis
51y

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expat

Post subject:

Posted: Sun Oct 23, 2005 2:32 pm

Joined: Thu Oct 20, 2005 8:14 pm
Posts: 66

Thanks for that Loren.
I will leave it alone.
John

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