Start off rich everywhere and slowly work on each circuit until it just starts to run smooth without much misfire.  Be careful trying to jet it by looking at the spark plug.  It is real dangerous to try to tune 1/4 through 3/4 throttle positions by plug chops and monitoring the spark plug.  Don't become another victim of the current fad of cutting spark plugs apart trying to get an accurate plug reading.  Remember when you look at a spark plug, you are not reading AIR FUEL MIXTURE or THE LEVEL OF POWER BEING PRODUCED...you are just see the operating temperature of the shell, ground strap, center electrode and the center wire.  The mixture does affect the operating temperature of all of the parts of the plug but so does the type of plug, the heat range, water temp, type of head and the length of time the engine is running near peak power.  The length of time the engine spends under hard load is very important when setting the main jet. 

A LT 500 does not spend enough time near power peak doing plug chops on a level road unless you have it geared for around 100 mph.  Typical gearing on a LT 500 limits your top speed to less than 80 mph.  On a level road the engine will easily over rev 500 to 1000 RPM past the power peak in 5th gear.  That is not the part of the power curve you want your main jet set for.   Lean main jets will almost always make the engine rev a little higher at the expense of making it too lean in the part of the power curve that produces the majority of the acceleration.  You really need a long steep uphill for setting the main jet or running it on a dyno.  The spark plug needs to experience the heat of combustion in the "right" part of the power curve long enough to reveal any detonation issues and any critical overheating of some of key areas on the spark plug. 

We have barrels full of burnt pistons from customers trying to jet their carbs by "reading" their spark plugs. 



Remember a two stroke that is just a little rich runs real well. 

Remember a two stroke that is just right runs real well.

Remember a two stroke that is just a little lean runs real well.

Remember a two stroke that is real lean runs real well until it seizes or burns the piston.