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Preparation
Thoroughly clean the piston and ensure all
traces of carbon are removed from the piston ring grooves. Check for
any signs of damage or wear. If more than 0.006ins can be measured
between a new parallel compression ring and piston groove, the piston
is extensively worn and requires replacement.
1 Check New Piston Rings for Gap in
Cylinder Bore
Remove all carbon deposits from the
cylinder barrel by light honing. This often helps to bed in a new
ring to the cylinder bore. The piston ring gaps can now be checked
using a feeler guage. Place each piston ring into the cylinder at
the bottom of the barrel (least worn part of the cylinder). The general
rule for air- cooled 4-stroke engines is 0.003ins per 1ins of bore
size, i.e. 75mm (3ins) should have a gap of 0.009ins on piston ring
when placed parallel in cylinder.
2 Fitting New Ring Set to Piston
Fit rings to piston grooves as indicated
on packaging (i.e. top towards crown of piston). Take care with compression
rings. These may have one tapered edge to avoid initial blow past
when bedding in. Now fit piston ring compressor to enable easy entry
into cylinder.
| Comments |
| David 5th March 01 | most useful, thanks
| | kfz 28th January 02 | The packaging does not always show correct fitment of the rings.
Secondhand rings are not always marked and the bevel edge is bedded in and worn down so as to be undetectable. Look at the ring carefully, the mucky side goes up and the shinney side goes down.
Kev
| | Tony 23rd July 02 | Quite ueseful but not much info on how to fit the rings to the piston without damage to either. After verifying you have correct, rings, gaps tops and bottoms and all is clean, lubricate piston well with light oil. Starting with oil control ring, DO NOT prize ring open and slide down surface of piston! With cast rings enter one END of the ring well into the appropriate groove and (well oiled remember!)twist the piston in your hands while guiding the ring in a spiral motion into it's seat, from the bottom up if it's a slotted cast iron opil ring and from the top down for the compression rings.
Multi rail steel oil rings with expanders are a doddle. The above method will avoid broken or stretched rings and big scratches down your shiny new pistons.
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