From the Society of Antique Modelers,
the Central Coast Chapter (26)
Shop Preparation for Engine Running
When we acquire a used engine that
flips over okay, and generally looks and feels like
it should run, it will usually do so. But, about
half the time it may need some tweaking to exorcise
some little problem that made the owner sell it. For
this, a good mechanic is more helpful than a priest.
For those of us who can’t or don’t like to run ’em
at home, there are some basic things to check out
before taking it to the field running session, and
maybe being disappointed.
Checkout amounts to more than seeing if an engine
props over okay and a glow plug lights. If the
engine is stiff or frozen up you’ll need to loosen
it first thing. A glow engine was no doubt run on
glow fuel, but if it’s a sparker, it might have been
run either on gas and oil or glow fuel. A glow plug
in the head and a missing timer is a pretty good
clue. A further test is to use a little of each fuel
on a rag to wipe away some of the goo. The fuel last
used will dissolve any residue the easiest. So, as a
minimum pull the plug and flush things out with a
fuel or solvent of the same base as the fuel last
used. It may require soaking. A frozen engine can
usually be loosened with a propeller installed and a
heat gun applied. How much pressure you can put on
the propeller without breaking anything is a matter
of experience. (If something breaks, you used too
much pressure.)
If the engine has ball bearings they need to be
checked more carefully once things have been
basically loosened up. With no propeller installed,
rock the crank back and forth with the piston down
below the exhaust opening. Carefully feel and listen
for any bearing roughness. More soaking, or even
disassembly may be needed. That’s because congealed
oil and/or even rust may be present. Congealed oil
can make bearings skid in their races on startup and
scuff the races or flat spot the balls. Sort of like
losing your skateboard halfway down the steel
handrail. Rust can be even worse, because it’s
abrasive and can grind up everything inside. Rust
has to come out and new bearings may be needed.
Fortunately, an old sparker that was last run on gas
and oil is much less likely to have internal rust,
or even bearings.
Most used engines are usually in really bad
condition. Probably the most common reason an older
engine won’t start right away is poor or no fuel
flow. Put a foot-long piece of fuel tubing on the
spray bar, blow through it and listen. You should be
able to close the needle so that no hiss is present,
then open it and hear the progressive hiss of
flowing air. If not, use fuel to flush things out
with the needle both in and all the way out. Check
alignment of the spray bar. Best position for the
outlet orifice is at right angles to the venturi’s
air stream or slightly downstream of that position.
If you look into the intake and can’t see the
orifice looking back at you, you’re probably okay.
Select the propeller you’re going to use, install
it, and flip the engine over to make sure the hole
size is correct and the propeller nut and washer
clamp down all the way.
Points on a sparker often have congealed oil, a
misadjusted gap, or other problems. Check that
points work by simply installing a continuity light
or Ohmmeter between ground and insulated point.
Slowly rotate the propeller and see that the light
or meter kicks on for almost half the revolution.
Check and set the timer advance at this time. Rotate
the piston to top dead center by feel, or by peeping
into the exhaust. Note the propeller position, and
rotate it backward, and watch for the light or meter
to kick on at about 20° before top dead center for
easy hand starting.
Make sure you have a clean tank and filtered fuel.
And if you have an external tank, or at least an
external fuel line, using an inline fuel filter will
eliminate a lot of potential problems. Check all
screws for snugness to be sure someone didn’t leave
something loose at some time.
For hand starting, a heavy leather glove is a good
idea. An out-of-time, or leaking crankcase on an
Ohlsson using gasoline can bang your fingers as
unmercifully as anything you’ll ever encounter.
Follow these steps as a minimum and you’ve just
improved your odds of getting things running during
the first attempt. Q
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