+4 timing etc...

[deckheight]

Ignition timing is usually advanced in order to acheive maximum combustion chamber pressures at a specific degree of crank shaft rotation, usually at or very near piston top dead center. Higher octane fuels require ignition timing advances due to their slower rate of burn, thus the burn is started sooner for the reason stated above. Higher octane fuels require more advance, whereas lower octane fuels require less...

High octane fuel or "race fuel" yeilds no more hosepower than a fuel with a lower octane rating. In fact too high an octane fuel for a specific conpression ratio will yeild less horsepower due to maximum combustion chamber pressures occuring too late and vise-versa. What higher octane fuels do allow are more efficient, higher combustion chamber compression ratios which are what is actually making horsepower. Where most engines/tuners get in trouble is from too low octane fuel for a specific compression ratio. Combustion chamber heat and pressure from too high a compression ratio causes lower octane fuel to self ignite before the spark plug initiates the burn... VERY BAD NEWS!

An easy and reliable indicator of correct ignition timing is how high up the spark plug center electrode soot has climbed. Viewed under magnification, soot should typically be within a few thousands of an inch below the top of the electrode. Higher than a couple thousands indicates ignition timing is retarded, too low indicates to much ignition advance. A better, more reliable, not so easy indicator is inspecting, under magnification, the exhaust side of the piston crown and corresponding head squish band area for pitting. Typically, ignition timing is advanced until pitting (detonation) is indicated then retarded one or more degrees depending on the tuners comfort level. There are other methods like detonation sensors, tachometers, etc. However, for 2-stroke engines... Marginal at best.

[714banshee380]

You need a compression tester. they are not too expencive.

 

 

where can you get one?

[deckheight]

Pretty much anywhere that sells auto parts. Prices range anywhere from something like $30 up to $200+ for non calibrated gauges. Try to find one w/an assortment of spark plug adapter's, specifically an adapter that matches the length of a Banshee spark plug and has a schraeder valve on the adapter, not up top near the gauger.

BTW, non-calibrated compression gauges are inherently inaccurate. Calibrated gauges are not much better for the intended purpose either. A compression gauge is not generally a recommended way to establish fuel octane requirements... However, a lot of people use the method and get away with it at least temporarily. Some don't. It is a much better indicator than nothing however, at least it is something...

Good luck.

Edited March 27, 2008 by deckheight

[714banshee380]

Pretty much anywhere that sells auto parts. Prices range anywhere from something like $30 up to $200+ for non calibrated gauges. Try to find one w/an assortment of spark plug adapter's, specifically an adapter that matches the length of a Banshee spark plug and has a schraeder valve on the adapter, not up top near the gauger.

BTW, non-calibrated compression gauges are inherently inaccurate. Calibrated gauges are not much better for the intended purpose either. A compression gauge is not generally a recommended way to establish fuel octane requirements... However, a lot of people use the method and get away with it at least temporarily. Some don't. It is a much better indicator than nothing however, at least it is something...

Good luck.

 

 

what would you recommend a way to establish fuel ratio mixtures?

[714banshee380]

....

[Wildcardracing]

what would you recommend a way to establish fuel ratio mixtures?

I use a ratio-rite to measure mine, 40:1 is what I run also. You could increase your oil to 32:1 and it might run a little cooler, but remember that if you increase the oil in your mixture it will lean out your air fuel ratio so you will have to rejet.