-
Before you disassemble
your engine, clean the engine and the rest of the paramotor. That
will reduce the risk of dirt and debris falling into the engine.
Once you remove the cylinder, stuff a clean rag down into the
crankcases.
-
The cylinder and head
use alignment pins to hold them straight in position from the
crankcases on up. The pins make it difficult to remove the
cylinder from the cases and the head from the cylinder. Sometimes
the steel alignment pins corrode into the aluminum engine
components. Try spraying penetrating-oil down the mounting studs
before attempting to remove the cylinder and head. Never use a
flat-blade screwdriver, chisel, or metal hammer to remove the
cylinder. Instead use this technique; buy a lead-shot plastic
mallet, swing it at a 45-degree angle upwards against the sides of
the cylinder. Alternate from left to right, hitting the sides of
the cylinder to separate it from the cases evenly. Clean the steel
alignment pins with steel wool and penetrating-oil. Examine the
pins closely. If they are deformed in shape, they won't allow the
engine parts to bolt together tightly. This can cause a dangerous
air leak or a coolant leak. The pins are cheap at about $2/£1
each. Replace them if they're rusty or deformed.
-
Never re-use old
gaskets. Remove them with a razor blade or gasket scraper. Don't
use a drill-driven steel wool type pad to remove old gaskets
because they can remove aluminium from the cylinder and head. That
will cause a gasket to leak.
-
Always check the ring
end gap on a new ring by placing it in the cylinder between the
head gasket surface and the exhaust port. The gap should be
between .012 to .024 inches.
-
Always install the
circlips with the opening facing straight up or down, that way
inertia will hold it tight into the clip groove. Place one clip in
the groove before installing the piston on the connecting rod. Its
easier to install a clip with the piston in your hand rather than
on the rod. There also less chance that you'll drop the circlip in
the crankcases.
-
Always install the
rings on the piston with the markings facing up. Coat the rings
with pre-mix oil so they can slide in the groove when trying to
install the piston in the cylinder.
-
Always install the
piston on the connecting rod with the arrow on the piston crown
facing towards the exhaust port.
-
The traditional way to
assemble the top end is to install the piston assembly on the
connecting rod, compress the rings, and slide the cylinder over
the piston. That can be difficult with larger bore cylinders, or
if you're working by yourself. Try this method instead. Install
one circlip in the piston, install the piston into the cylinder
with the pin hole exposed, install the piston pin through one side
of the piston, position the cylinder over the connecting rod and
push the piston pin through until it bottoms against the circlip,
install the other circlip. It only takes two hands to install the
top end using this manor and there is less chance that you,ll
damage the rings by twisting the cylinder upon
installation.
-
On cylinders with reed
valves and large oval intake ports, take care when installing the
piston assembly in the cylinder because the rings are likely to
squeeze out of the ring grooves. Use a flat-blade screwdriver to
gently push the rings back in the grooves so the piston assembly
can pass by the intake port.
-
For steel head
gaskets, place the round side of the "bump" facing up. Don't use
liquid gasket sealer, use aerosol spray adhesive types instead.
For hybrid fibre/steel ring head gaskets, place the wide side of
the steel rings facing down.
-
When you initially
start the engine after a rebuild, manipulate the choke to keep the
engine rpm relatively low. Once the engine is warm enough to take
it off choke. Keep it under 2/3 throttle for the first 30 minutes.
Two common myths for proper engine break-in
are:
