How to Break In a Nitro Engine Properly

RC Car
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Proper nitro engine break-in is critical for the long-lasting performance of your RC. Every new nitro engine should undergo a break-in procedure which takes from one to two hours and about three to five tanks of nitro fuel. Be patient! If you break in the nitro engine properly, the upkeep on your RC vehicle will be less costly than if the procedure is done hastily and incorrectly.

Break-In Procedure

Choose a clean, flat, paved or smooth surface. You'll be doing the initial break-in with the body off so you don't want to be kicking up dirt or flipping the while. During the first couple of tanks of fuel, focus on varying and limiting your speed. Don't run your engine past half-throttle and don't run at a constant speed.

During break-in, deposits build up and can foul out the glow plug, so your engine might seem like it's stalling or not running properly. This is normal. Proper break-in alleviates these symptoms. Have an extra glow plug or two handy in case you need them.

Operate Safely

Here are simple safety checks you need to do before starting:

  1. Turn on the Controller First
    Turn your transmitter/controller on first, followed by the receiver on the RC. When finished running your RC, turn the receiver off first, then the controller. This sequence will keep your nitro RC from running amok if someone nearby is running on the same frequency. Do yourself a favor though and check frequency before running your RC.
  2. Put the Engine in Neutral
    Move the throttle forward and reverse to ensure your nitro engine is in neutral and that it's is in the idle position when the throttle is released.
  3. Check Your Steering
    Move the steering controls from side to side. If steering seems sluggish or hesitant, replace the receiver's batteries before proceeding.

Prime Your Nitro Engine

Start up your RC. Watch to see if fuel is moving through the lines. If fuel doesn't reach the carburetor after 3-5 seconds, place and release your finger over the tip of the exhaust for a couple of seconds to help the engine start. This is known as priming the engine. Be careful when doing so because if too much fuel goes into the engine when priming, it will flood, causing the engine to lock up.

If the engine does flood, use your glow plug wrench to remove the glow plug. Place a rag over the engine head. If equipped, use your electric starter. Start the engine to get the remaining fuel out and wipe off the head with a dry towel to remove any remaining fuel. Reinstall the glow plug and start on the first tank of the break-in process. Your nitro engine shouldn't be primed for more than 1-2 seconds at a time to avoid flooding.

Do a Five-Tank Nitro Engine Break-In

With each tank of fuel, you'll increase the amount and duration of the throttle. Use these tank-by-tank guidelines for your nitro engine break-in.

Tank 1:
Give the engine one-quarter throttle slowly for 2 seconds. Apply the brakes. If you pull back on the throttle too fast, you may cause your engine to stall.

When there is a nice trail of blue smoke coming from the exhaust, it means your fuel mixture is properly set and the engine is being lubricated. If no smoke is present, enrich the fuel mixture by giving the air/fuel mixture needle a quarter turn until smoke is present.

Continue running the first tank of fuel, repeatedly giving it one-quarter throttle, then braking until it is almost empty. Do not run the tank dry because this will result in a burned out glow plug from the fuel mixture being too lean; it can also lead to damage from high engine temperatures.

Shut off the engine by pinching the fuel line to the carburetor; let it cool down for about 10-15 minutes before you start on your next tank of fuel.

Tank 2:
Advance to half-throttle for 2-3 seconds for the second tank of fuel. Remember to accelerate smoothly through the entire break-in process. Do this repeatedly as long as you have fuel. When the second tank is done, repeat the shut-off and cool-down steps as you did in the first tank of fuel.

Tank 3:
On the third tank of fuel, run for a 3-second count at half-throttle, then brake. By this time the engine begins to loosen up, the idle may need to be adjusted down.

You will know an idle adjustment is necessary when your nitro RC won't sit still when idling. Use your tuning screwdriver to turn down the idle by turning the idle adjustment counter clockwise to reduce the idle speed. From this point forward you don't have to let your engine cool down between tanks.

Tank 4:
For the fourth tank, give your nitro RC full throttle for a count of 3 seconds and then brake. If your nitro RC is equipped with a multi-speed transmission and tries to shift into another gear, let off the throttle and then brake. When doing a 3-second count on tank four, remember to accelerate smoothly to avoid doing wheelies or flipping the RC over.

Tank 5:
For this final tank of fuel, repeatedly accelerate to full throttle in 3 seconds and hold for 2 seconds, then brake. After this tank is done, the break-in process is complete.

Maintain Your Nitro Engine After Break-In

After break-in and following each session with your nitro RC, you'll need to perform after-run maintenance. For a nitro engine this includes:

  • Draining the fuel tank
  • Cleaning and oil the air filter
  • Adding after-burn oil