To Assemble The Piston - Husqvarna K970 III Workshop Manual

Examine the product to see if it has broken down
because of an incorrect oil mixture, or no oil at all. If
there is oil on a piston that is too hot it can carbonize. If
not, check if the connecting rod or the crankcase has a
thin layer of oil.
If there is sufficient oil, inlet leakage can be the cause.
When the engine leaks air on the inlet side, the fuel/air
mixture changes. This causes scoring, mainly on the
exhaust side. Look for scoring damage in combination
with a piston top that has become too hot.
6.9.4 Too hot piston top
If the engine has been too hot, aluminum particles are
frequently found on the top of the piston. This can cause
the piston to melt.
Too much air in relation to the fuel volume increases the
temperature in the combustion chamber. Examine if the
inlet system is blocked. Examine that the fuel supply has
not been blocked by a defective fuel hose, tank vent or
the pulse hose.
Gasoline with a too low octane grade can cause ignition
at the incorrect position. Spark plugs with incorrect heat
rated value can cause the same problem. They can
increase the temperature in the combustion chamber.
Make sure that the key on the flywheel of the crankshaft
is not damaged. The flywheel position on the crankshaft
controls the ignition point.
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6.10 To assemble the piston

Lubricate new or cleaned bearings and piston rings with
2-stroke oil before you assemble them.
1. Make sure that the arrow on the piston points in the
direction of the muffler when you assemble the
piston on the connecting rod.
2. Install the needle bearing in the connecting rod.
Repair and servicing - 47