Breaking-in the Top 80

by Had Robinson
updated April 2, 2021

Why break-in an engine?  The new moving parts fit together tightly and, as a result, create much more friction (and heat) until they wear a little bit.  Not giving these parts the right amount of time to wear and adjust to each other will cause excessive heating and will permanently damage them.  A proper break-in will provide a better running engine and longer life.  Sadly, most engines are not properly broken-in.  It takes time.  Remember that running at full throttle on a new engine for more than a 30 seconds should never be done.

It takes dozens of hours in the air to get comfortable with the throttle so you are not thinking about it.  We all have enough distractions as it is.

The more the throttle is second nature to you, the less task saturation you will experience.

Do not increase the amount of oil in the fuel during the break-in period.  The reason is that it causes the engine to run hotter and may even cause it to seize.  Do NOT listen or pay any attention to the BLOGS or anyone who thinks he knows more than the people who engineered and manufactured the engine.  (The source for adding more oil during break-in largely comes from outboard motor manuals.  These engines are water-cooled and cannot overheat.)

Put the engine on your back and take a walk.  Not only will you break the engine in but you will get used to it being on your back.  Task saturation is a very serious issue for new pilots and why it is useful to walk around.  You will be running with an engine that is at or near full throttle and must get used to it.

It is highly recommended that a CHT be installed along with a tachometer.  It is cheap money that will tell you what is going with your engine.  Why bother?  Most of the engines that come in here were destroyed by overheating.  If you do not have a tachometer installed, you will have to guess the speeds below.

Here is a PDF of the steps below.  Print it out so you can refer to it as needed.

  1. Start the engine and let it idle until the cooling fins are too hot to touch (CHT temp of 70C).  Idle it for another (10) minutes.  Do not exceed these times because it will foul the spark plug.
  2. Vary the RPM up and down from idle to 4,500 RPM and back to idle at 1 minute intervals for 20 minutes.  Stop the engine and let it cool to the touch (< 40C).
  3. Restart the engine.  Vary the RPM from idle to 4,500 RPM at 1 minute intervals for another 20 minutes.  Stop the engine and let it cool to the touch (< 40C).
  4. Restart the engine and let it warm up (70C) for 10 minutes at a fast idle.  Vary the RPM from idle to full throttle (no more than a few seconds) at 1 minute intervals for 20 minutes.  Stop the engine and let it cool to the touch (< 40C).
  5. Check the head nuts for the correct torque (9 Nm).  This is very important.  THEY WILL LOOSEN.

At this point, you can fly.  Vary the throttle often during the break-in period.