1982 430 Cr squish tolerance

A friend of mine gave me gave me some porting tips on the 430? Also a lot based of of the bulletin.
What he can't remember is the squish tolerance recommendations before having to use race gas while still using pump premium. Does anyone know?

1.2-1.4mm should be fine.

I have a friend that runs his Yamaha with a Noleen/Öhlins 360 cylinder and a C-R of 15.1-1 on 95 Octane.
But that engine is a one of a kind.

My 420 cylinder head has the squish already machined in it. It has a compression release too the old style spark plug threaded hole one. Interesting stuff.

We have to be on top of our game to realize what's been reworked already to these used parts.

Just measured my 500 and it has 1.45 mm squish and a 51cc head witch give it a Compression ratio of 10.6:1
No problem on 95 octane.

Ok, thank you that is good to know. What formula did you use to figure all that out on yours?

I use a tuning program.
I need Bore and Stroke and you have to measure how much cc your Combustion chamber is.