The performance Tuner is a very sensitive and highly accurate portable measurement device.   It is a simple, one button operation.

Here's what it can do for you:

1. Provides data that can be used to decide if a change to your engine's tune is needed;
2. Accurate within 3%;
3. Light weight and portable; can fit in your toolbox (recommended to keep wrapped in light-colored towel or similar in order to minimize solar heating effects from the sun, etc.)

Use either the ADR (% of STD air density), Density Altitude, or Air Density value, or any combination of readings.   You will need to build a data base to help determine when there has been enough of a change in the air conditions to warrant either an increase/decrease in jet size or even a timing change.

For further information, the following are some of the many sources on the Internet:

Two Stroke Jetting TZ 250 Jetting
Tuning for the Weather; Hot Rod, June 2004 Hot Rod
eKarting News ekartingnews and check the forums
TZ250 Racing TZ250Racing and check the forums
RS125 Tuning Fear of Jetting