You
will not see complete and comprehensive printed directions for breaking in an
ABC (aluminum piston, bronze sleeve, chromed) type motor to get the maximum
performance from it.
In
a proper break in there are two things that must happen in the first two
minutes of run time, and the initial heating of the liner (bronze sleeve chrome
plated). As much heat must be put into the liner as possible to gain the most one
time thermal expansion. The difficulty
is in getting it as hot as possible without the engine being run lean because
the connecting rod bushing need plenty of oil.
The
best way to accomplish this is to run a very small prop (two inches less in
diameter for a .15 or .25) in the 24-25K rpm range with the needle set to a
clean 2 -cycle setting with a noticable increase in rpm's when fuel line is
pinched.
After
starting you should get the needle set very quickly and let it run for about 1
minute maximum then stop it and let it cool completely. After it is has cooled run
it again for about 2 minutes and shut it off allowing it to cool completely. Then
run a tank full and pinch line very so often to bring it both peak rpm and peak
temperature. After this third run the
engine is ready for combat.
OEM's
will not risk putting any peak potential break-in in writing for fear that some
may interpret heat as lean. I am sure there are many different ways people will
break them in but this is method is proven and works well.
Go
to www.JETTENGINEERING.COM
and read his comments on engine break-in's. This initial heating is so critical
that he sells his engines with the initial running already done and guarantees
minimum rpm's. If he left it up to the owners results would vary.