For Break-in, we recommend a known brand of petroleum-based 2 stroke lawn
mower oil. Use of high quality synthetic oils will only prolong the running in time
on a JC engine, in particular those engines with two large piston rings. Outboard oil
is not recommended for use in air-cooled engines.
A mix ratio of 30:1 is recommended for the initial beak in period (aprox. 10 litres of
fuel), changing to 40:1 mix for a further 10 litres. For best results, allow the engine
to run between 6,500 and 7,000 rpm with adequate cooling during break in and make
sure that the engine is not operating on the lean side. Thereafter, continue operating
on the 40:1 mineral oil mix or switch to one of the high performance two stroke oils
for air cooled engines and mix according the oil manufacturer’s instructions.
The engine should be set on peak. Avoid the tendency to run rich as per glow
motors, this only serves to foul the plug and carbon up the cylinder.
Break In
The JC 120EVO have single piston rings and will reward proper running in with
good performance and a substantially longer life. We don’t believe in lengthy bench
running and would far rather see the engine flying at varying throttle settings but not
subjected to hard flying for the first two hours, that is really only eight 15 minute
flights.
Propellers
Always check the prop bolts and inspect your prop and spinner before each flight.
The bolts should be checked for correct tightness and not tightened more and more
each time. While special break-in props are not required, avoid loading down the
engine during the break-in period, as above, let the engine spool up.
The safest way to drill mounting holes in a propeller is to use a drill guide for your
engine. The next best is to use a drill press, using the prop washer as a guide. Drill
from the
back
of the propeller to ensure that the exit holes are perfectly in line with
the associated holes in the prop hub. Bear in mind that multi bolt hubs have a central
shaft for accurate propeller location, the mounting bolts are there to keep the prop on
the engine and transfer torque. If the prop does not track, replace it or attempt to
reshape the seat area – do not crush the prop in an effort to correct the tracking by
inconsistent torque on the bolts.
