Cool head questions

[MossboysRacing]

I did some searching before i asked, but I still have a few questions. I bought a pro design cool head and it came with a 21cc dome. This should be pump gas if i remember. My questions is, will i have to go to 50/50 pump/race if i switch to a 89 cr250 gasket? I know that bumps up compression some. Also, where can i get the dome O-rings at? Im running a cast pro-x piston on stock cylinder and stock head. Will higher octane gas trash the cast piston? Im just trying to get my ducks in a row so i can put this together in one shot, hopefully w/o any problems. Thanks John

My current motor is stock 86 cylinder and head bored .050 over, cast pro-x piston, v-force 2, fmf fatty, lightened flywheel, mild proting, 38A/S

[superevil]

The stock 3 layer metal gasket is .060 thick. If the cr250 head gasket is thinner,like if its .020 thick,then it will bump your compression up.
If your deck height is stock,then you might get away with a cr head gasket and 21cc dome on pump gas,but i would check your conmpression and squish first.
Usualy at about 175/180 psi you are borderline for race gas.
As for squish i wouldnt go any tighter than .040 to be safe.

If your reason for not using the stock gasket is to get away from the three layer metal,you should look into getting an 86ATC250r head gasket. It is a regular style head gasket(metal mesh with coating) but it is really thick like the stock trx gasket,so it wont change your squish very much.

[Sandsjbyz22]

My old R had a similar setup as yours. I found that I used to blow just about every head gasket with this setup other than the stock TRX gasket. We tried alot of different things but we always had to come back to the stock Honda gasket.

[MossboysRacing]

Now dont laugh, but how do you measure squish? As far as I know, the cylinder has never been decked. In years past i just put the new stock headgasket on and torqued to factory specs. I have a compression tester at home, and if i remember correctly, i want to warm the engine up and then check compression? Or am i wrong? Thanks

[deathman53]

actually the atc head gasket is thinner than the trx and it is nearly the same meterial, just the center piece is thinner. No stock honda head gasket is the metal mesh coated, thats aftermarket there.

[superevil]

Originally posted by deathman53
actually the atc head gasket is thinner than the trx and it is nearly the same meterial, just the center piece is thinner. No stock honda head gasket is the metal mesh coated, thats aftermarket there.

I have bought 3 head gaskets from my honda dealer for the atc250r and they werent anything like the trx head gasket,maybe they werent selling me stock,but they didnt specify.They might have ordered me aftermarket

As for squish and deck height--If you have your cylinder head off,turn your motor over till the piston is top dead center.If everything is stock,The edges of the piston should be just below the cylinder deck,not even or above it.
If your deck height is stock then you shouldnt have a problem with to tight a squish.

Squish check. Take a few inches of solder. Bend It into an "L" shape. Take out your spark plug. WIth the piston down,put one end of the solder into the cylinder(dont drop it in) and hold it to where the solder goes to the side and is touching the sleave.
Then turn the engine over once (gently) squishing the solder between the piston and head on the edge. Then take it out and measure the thickness of the squished solder with a micrometer. Do this on the left or right side,not front to back.
The thickess of the smashed solder is your squish clearance.

I would just throw it together with the cr head gasket and check the compresion. If your under 180,then you should be able to run some pump gas