THE FOUR RULES OF ENGINE TUNING

1. Rich is good. Blue smoke should always be coming from the exhaust.
2. Always set the high-speed needle first
3. Never try to tune a cold engine—wait for it to get up to operating temperature.
4. Always begin your engine tuning from a rich high-speed needle setting. Never start out with a lean setting.

Tuning all carburetors and Engines for the experienced racer:
1:
when starting a new engine follow the set up instructions first! Start the engine and let idle at a moderate speed for two or three minutes. Then shut it
down and let it cool for a few minutes. Be sure the piston is not at the top. Repeat this procedure three or four times.

2:
Now run the engine on the track, making sure the engine is rich. You should hear a “four cycle” sound. Be sure to let off the throttle going down the straightaway once or twice so the engine is not straining in its rich condition. Repeat this procedure for three or four tanks of fuel, letting the engine cool several minutes between tanks. Also, check the glow plug often. It should look new (shiny wire that is not distorted).

3:
You can now start leaning [turn clockwise] the maximum needle a little at a time in one hour increments [imagine the needle like the hour hand of a clock] checking the glow plug often. [I use a glow igniter with a meter on it] I recommend running a few more tanks a little on the rich side before “Race tuning” When tuning for maximum performance [Race tune] adjust until engine will reach Good RPM then open needle 1/8 to 1/4 turn.

4:
set the low end or idle:
After getting top end set close, bring model in, listen to the idle. If it is idling fast then it slows down in a few seconds, it is probably too RICH on the bottom (minimum spray bar). In that case, make it more lean (turn clockwise 1-2hr (clock method) turn), then run another lap and bring the car in again.
Repeat this procedure until the idle stays high for at least 10 to 20 seconds; at this point readjust the airscrew ( idlescrew ) so the idle is at a moderate speed. The wheels should not turn, and the clutch should be fully disengaged.

If you had to turn the minimum spray bar in more than two or three more turns recheck the slide adjustment! [Picco Torque
carburetor only]

5:
you may need to repeat steps 3 and 4 several times to achieve the “perfect tune”
Be patient. Tuning is the hardest part of gas racing, and is the first secret to race winning results. If you are a beginner, it is highly recommended that you ask your hobby shop or an experienced modeler for help.

Three last tips

1 Be sure engine is warmed up before tuning
2 always tune from rich to lean. When in doubt, richen up the maximum needle (top end)
3 If you have to turn minimum spray bar (low end) in more than three to four turns from flush, it is a indication the slide adjustment is too loose and
needs resetting (Picco Torque carburetor only).

Good Racing,
Ron Paris
Paris racing

another good chart

TUNING
This chart indicates the direction in which you should adjust the fuel mixture when faced with changing weather and other conditions. It assumes the engine is currently well tuned. You could face any combination of conditions listed in the chart; knowing which way to go with the mixture adjustments is half the battle.
Higher air temperature Lean
Lower air temperature Rich
Higher humidity Lean
Lower humidity Rich
Higher barometric pressure Rich
Lower barometric pressure Lean
Higher altitude Lean
Lower altitude Rich
Higher nitro content Rich
Lower nitro content Lean
Higher oil content Lean
Lower oil content Rich
Hotter glow plug Rich
Colder glow plug Lean