Honda Spree and Elite 50 Forums

A standard improvement for any engine has always been to bump up the compression.
I was talking to the guy at a local scooter workshop about it. he swears and declares its a step backwards to shave the head, (Due to reducing the squish pad area) and better to remove material from the barrel instead.
conventional wisdom for a spree was that .020 was a safe bet.
is that going to be a safe bet?

Higher compression ratios produce more power, up to a point. The more you compress the air/fuel mixture, however, the more likely it is to spontaneously burst into flame (before the spark plug ignites it). Higher-octane gasolines prevent this sort of early combustion. That is why high-performance cars generally need high-octane gasoline -- their engines are using higher compression ratios to get more power.

That being said, I have no true answer to your question on removing .020 from the top of jug. Keep in mind that if you remove too much you'll get piston slap or end up with a compression TOO high. This can be remedied by adding head gaskets but it would then change the squish and reduce compression. Its best to have a spare jug on-hand just in case your test subject goes terribly wrong.

Please come back and post your findings and results...

If a bump in performance is what youre after without breaking the bank (or the sound barrier) I suggest a Polini Contessa. Its easily swapped in while still using the stock exhaust, etc...

Wheelman111 has deep knowledge in this kit and what it would require to adapt it to an otherwise stock motor.

A couple of hundred usd defiantly breaks the bank. Pulling the barrel and knocking half a mm off it is only going to cost me a cost of gaskets.
I guess I need to see what my piston to head clearance is now, and skim it accordingly.
Perhaps a better question would have been,
What's the minimum safe piston to head clearance?

I'm not too concerned about detonation. More about the piston and the head trying to make love to each other.

Measure squish and deck the bore accordingly. You want it in the .8-.9 range. For race engines that are gonna run race fuel .6-.7 is usually the squish.

Thanks