Puch Cylinder Head Compression Ratios

How do you calculate compression ratio? I may need better gas...or DO I? I have a Very high comp head (into the fins by a gnat's ass). Does anyone know the cutoffs for grades of gas, so I don't preignite? I have just been using 85 octane/Yamalube.

Re: Puch Cylinder Head Compression Ratios

well a rough compression ratio is found by getting a compression tester and dividing the number shows by 14.5, in order to get true compression ratio as opposed to compression ratio you need to first take the head off and move the piston until all ports are just barely closed, then fill the cylinder with paraffin that you carefully measured out and do the same with the head then you divide, if you are running 12:1 compression then you need high octane gas 11:1 just run super, 10:1 medium and so on, basically run whatever you can without detonating im basically skimming over this as if you arent seeing any problems now that your probably fin, check your sparkplug for white spots and your piston and head for them also thats a sign you are detonating

Re: Puch Cylinder Head Compression Ratios

Try some octane booster if you are over 14.5:1. Detonation is the issue and it is usually obvious when it happens. The engine will seem like it is fighting it'self and thats exactly what its doing

Re: Puch Cylinder Head Compression Ratios

Also a side note is a deteriorated piston espically around the edge above the ring(s) or on the crown.

Re: Puch Cylinder Head Compression Ratios

Cool thanks, I should figure this shit out.

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