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Old Yesterday, 11:05 PM
Gibnut Gibnut is offline
Join Date: Jan 2018
Posts: 64

Originally Posted by Jakobi View Post
Bugger me..

Combustion chamber cc's at 21.5cc
250cc piston dome has always been around 6.6cc
Volume of 1mm squish clearance is 3.46cc

Total trapped Volume 21.5 - 6.6 + 3.46 = 18.36
Compression Ratio (18.36 + 249)/18.36 = 14.56

Bit high I think..

If.. it was cut to 1.25mm as requested the ratio would down to 13.93:1 ...which is where my old 2010 was set. Last bike was 13.2:1

So so so.. Where to from here.
Mine went down to TSP twice as well.

Also, after you rip the 5mm thick gasket, check the retainer nut on the PV actuator rod thingy - mine had backed out all the way down the thread.

Gas Gas 2018 EC250 Six Days
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Old Today, 02:23 AM
(F5)'s Avatar
(F5) (F5) is online now
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Join Date: Jul 2006
Location: Wellington New Zealand
Posts: 1,113

My 300 is running just under 1mm so that is fine, can take out of chamber to reduce ratio to where you need it which is lower.
'07 EC300
496 CPI Cheetah RZ/RGV hybrid
675 Street Triple R
RS125 framed MB100 racer
Stinger T125 Suzuki
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