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pro design domes
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Posted by: danbobsR

I just bought a 270 cylinder and the guy told me I should only run a 23cc dome. nothing with a smaller number cc's why would he tell me that and does anyone have a 23cc dome they want to sell?

Posted by: GPracer2500

quote:
Originally posted by danbobsR
I just bought a 270 cylinder and the guy told me I should only run a 23cc dome. nothing with a smaller number cc's why would he tell me that and does anyone have a 23cc dome they want to sell?

He might have told you that to keep the compression in the pump gas range. Just a guess...

Posted by: danbobsR

he had asked me what kind of fuel I was going to run I told him 108 or 110.

Posted by: deathman53

it might be as the compression would be too high. I know the cool head on my atc250r, I used a atc gasket and a 18mm done, it required race gas, I changed it to a cut stock head and atc gasket for less compression. It ran fine on pump gas that way.

Posted by: baker250r

im runnin a 24cc dome in my 270pv. and i run race gas.

Posted by: 250r4life

24.... that seems awful big.... i had a 19cc in my duncan 265, and i actually just got a 21cc to lessen up the compression a bit... duncan had to custom make it, as their producation domes are 17-19cc's...

Posted by: danbobsR

somebody correct me if im wrong here but I put the cylinder on the bike the dome of the piston is actually a hair above the deck Im guessing with that and a split stock gasket that is why he told me to run a 23 or larger cc dome Im guessing the smaller the cc the closer the dome is to the piston? so a 23 would give me more "head room" should I say.

Posted by: 250R_4_ever

Right

You can run a 23cc dome size and requirer race gas while another engine will be on pump gas

-This can be Explain by a different Spacer plate size.
-Different pistons
-Shave head

and who know what .

tried a taller headgasket if your head is on the non oring system
you my raise you dome to a true 23cc

Posted by: 86 Quad R

another thing i'd like to add. since the piston is coming up out of the cylinder. the previous owner may have had the original dome relieved for squish tolerances.

regardless of what dome/head gasket combo you decide to go with i suggest that you check the squish at the "outter rim of the piston with everything in place and torqued down.

also compare the new dome with the old dome to see if the squish band at the edge hasnt been releaved for the higher piston TDC(top dead center.
juss my .02