750 cylinder barrell very flat top

Jim at JSMotorsport recommends you use Permatex Motoseal #29132 on the copper base gasket on his web site.
JUG

Hi All.
I have replace today the barrell flat top whit the copper base gasket bought from JS MotorSport.
The pistons protrude of 4 mm out the barrells.

With the copper cylinder head gasket the pistons protrude out 2 mm.

With the alu gasket the pistons do not protrude out.

With copper and flame gaket the pistons do not protrude out.

I cannot change this barrells.
What i should do?
Only copper, alu, or copper plus flame, gasket?
I mean you do not like alu gasket.
Please, i need your advices.
Thank you.
Piero

Relax - 750 all allow standard pistons to extend above cylinder - until spacer and gasket added to set compression ratio and/or valve/piston clearance. Main issue is make sure pistons not rubbing on gasket and valves miss piston rise enough. Secondary for racers taking chances with shaved head or taller pistons is spacing the piston/head squish/quinch gap, which is not a concern in stock engine assembly, especially with base plate and standard Norton gaskets. Someday soon you will spank its kicker to hear its first sounds of combustion life.

I complete the informations.
The pistons protrude out the top of barrells of 4 mm.
The head squish area is 4 mm.
The copper head gasket is 2mm with his thickness that will be reduced of 0,10 mm when the studs are tightened.
So the clearance will be 1,9 mm.
Is it enough???
Thank you.
Piero

1.9 mm is about .075 inches and as racers use about .040 inch 1mm or less - so yours is over safe clearance after torque down crush. Piston/head clearance over .06 inch or 1.5 mm eliminates squish gap * quench band effect, which is a non issue in Nortons as some hi power race engines have no squish at all.