Many times a fouled or dirty spark plug which has
caused trouble will prove serviceable after it has been
thoroughly cleaned, washed, and properly gapped.
WHEN SETTING GAP BE SURE NOT TO
DAMAGE ELECTRODES OR INSULATOR.
THE PROPER GAP IS .035 ".
Replacement spark plugs are made in wide heat ranges
to suit different engines.
Always install spark plug tightly so air cannot
leak into the firing chamber.
When trouble-shooting, it is advisable to use a new
spark plug, or one of known performance --at least until
the trouble has been located. Plugs cleaned by sand
blasting must he thoroughly washed to remove all
TROUBLE SHOOTING ENGINE
In order to start and run, an engine needs
CLEANING EXHAUST PORTS
CYLINDER COOLING FINS
(5 and 6 below)
The fins and the surrounding area should be kept clean
Here are some simple checks you can perform:
and open for maximum cooling.
1. With tank full and fuel cap off or loose, fuel should
MUFFLER, EXHAUST MANIFOLD AND EXHAUST,
run from tank when the fuel line is disconnected at
Occasionally, the muffler and manifold should be
2. If engine stops with cap tight, but runs with the cap
disassembled from the engine and separated from each
off, the cap is not venting and has to be replaced or
other to permit checking for carbon. Any carbon
clogging the perforations in the inner tube of muffler can
3. Run engine with filter on and with filter off. If there is
be picked out with a bent rod or scriber. (See fig
a difference in performance, the filter is dirty.
20)How often to inspect the muffler, manifold. and the
4. Always keep exhaust ports and muffler clean.
cylinder exhaust ports depends on how much the unit is
5. Magneto can fire only with switch "on."
used- the exhaust ports(fig 21)should be cleaned when
6. The firing end of the spark plug tells a story:
they become more than a third clogged with carbon.
FIRST, put piston to top dead center (covering the ports
IF THE PLUG IS DRY even after you have cranked the
so the scrapings can't fall inside), THEN, remove the
engine several times with the choke pulled out, it means
carbon carefully with a wooden scraper. Be careful not
fuel is not getting into the combustion chamber. Check
to scratch the piston or damage the chamfered edges of
1, 2, 3
the exhaust ports. Blow all loose particles clear of
engine before installing manifold and muffler.