Engine Break-In

by Had Robinson
updated November 11, 2022

If your paramotor has a specific break-in procedure, follow it carefully.  If not, the general steps below should be adequate to protect your engine and give it a long life.

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 minute should never be done.

The procedure can be done with the paramotor on your back.  If you are a new pilot, it is the perfect time to become more familiar with the feel and sound of your paramotor.

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, the safer pilot you will be.

Do NOT increase the amount of oil in the fuel during the break-in period unless your engine manual specifically advises you to do so.  Polini, Minari, and Miniplane note that increasing the oil in the gasoline should not be done.  The reason is that it causes the engine to run hotter and may even cause it to seize.  DO WHAT THE ENGINE MANUFACTURER SAYS.

Do enrich the fuel air mixture if you have an adjustable main jet.  As the Air Conception manuals note, the fuel in a 2 stroke engine is also used to cool it and why only partial completion of the fuel burn is preferred.  That is, never lean out a main jet to get the most performance as this will burn up an air cooled engine.  Instead, use a CHT to lean out the engine, always keeping the head temperature within the range recommended by the manufacturer.

• Do NOT pay any attention to the BLOGS or anyone else 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, something important when foot launching.   While doing the break-in, fiddle with items around you like the buckles, the choke, etc.

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.  The technique given here is more than most engines require, to be safe.

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 or what your engine manual specifies) 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.  THEY WILL LOOSEN!  Here's what your head will look like if you don't do this.  The exhaust gases continually blew out the space between the head and the cylinder.  Engine did not run very well.  This can warp the head.
   

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

DO NOT FLY AT FULL THROTTLE FOR MORE THAN A MINUTE UNTIL YOU HAVE RUN 10 LITERS OF GASOLINE THROUGH THE ENGINE!

IMPORTANT: Polini and Minari note that break-in is complete after two tanks (20 liters) of fuel has been consumed.  Be really easy on the throttle until (20) liters of fuel have been consumed.