polini head modifications

2 Stroke Modification and Performance Tuning (Keep it technical!)

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polini head modifications

Postby handsomejackuk » Fri May 18, 2012 2:22 am

Hi.

Is there any modification that can be done to the original polini head to increase compression. ? Can i get it milled down currently measures 27cc volume. Dont know what that equates to in compression. On my lml with polini barrel

Any thoughts on this ?


Al.
handsomejackuk
StellaSpeed Silver Level
 
Posts: 431
Joined: Wed Sep 30, 2009 5:56 pm
Location: uk.k.
Scooter(s): lml 125 star dlx

Re: polini head modifications

Postby handsomejackuk » Fri May 18, 2012 3:14 pm

need a bit of advice on this.. trying to work out compression ratio....

i have the bor and stroke 63mm X 57mm which is (PI X 63 X 63 X 57)/4000 =177.592 cc

squish is 1.2mm dunno how to work out the cc but guessing (PI x 63 X 63 x 1.2 ) /4000 = 3.738cc.. not taking in to consideration the dome of the piston !!!

head volume is 27cc measured by syringing oil in to the head with spark plug installed.. and the head held level... i did not use a plexiglass plate !!! so this is the best estimate so far...

so compression=

(177.5 + 3.7 + 27) / (3.7+27) =
208.2 / 30.7
= 6.78 : 1

surely thats not rite...!!!!

where am i going wrong here with the maths....???

anyone....

does 27cc seem a lot for standard polini cylinder head... (anyone measured this ) ?

can anyone give me an estimate of volume with 1.2mm squish...( inlcuding the dome of the piston) ?

do i need to measure the height that the exhaust port closes and use that for the cylinder capacity... would anyone know what that would be on a polini 177 barrel... standard crank, LML cases with real thin gasket...just for me to get familiar with the figures... to save me pulling the head off right now...

Al...
handsomejackuk
StellaSpeed Silver Level
 
Posts: 431
Joined: Wed Sep 30, 2009 5:56 pm
Location: uk.k.
Scooter(s): lml 125 star dlx


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