compression ratio

[GreenMachine]

Can some one help me with figuring out my c.r. I milled about .008 off the head then lapped it flat. Also lapped my jug flat also. I have 45cc's in my head. standard square bore 500 (86mm x 86mm) This is where I am getting trumped. I am running a wiseco pro light and the center of the piston is above the deck by .030 of an inch. The outer portion of the piston is .010 below the deck. and head gasket is .015 thick. I can figure it with a flat top piston, or even a dished piston, but I don't know how to figure it up with the piston above the deck.

Thanks for any help,
Jody

[CR480R]

put a lil grease on the rings and fill the fill the combustion chamber through the spark plug hole....with the piston a tdc of course...

[BDI]

I come up with 11.3:1  I added your deck hight to the gasket thickness and figured the piston dome at one cc. Using some oil to cc your trapped volume Is a good way to do it like cr480r suggested but rember to add the spark plug cc. I can't remember how many cc's a plug holds but I do remember it's enough that you need to figure it in.

[kaw rider]

1.8cc. depends on what plug you have.

[Brett]

When working out your compression ratio with a two stroke you should take into account the effective compression ratio which is only using the stroke from when the transfer and exhaust ports have been closed off

[stewart]

i think that is a good thing to keep track off the figured compresion from the top off exhboster ports  to top deadccenter volume ..........but i think in a two stroke that the rpm  and the diamter of the exh pipe stinger and cone giong into the stingers vary the amount of pressure that  is created in the cylinder ..so these cylinder head ccs and compresion numbers  become refrence numbers ,, and we can find combos that work very well or not with a given fuel timing or pipe..so it  helpful to look at sevral comprsion figures in a given moter,,