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AJH[_3_] AJH[_3_] is offline
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Default Sthil ms260 rebuild

On 23/04/2021 23:27, T i m wrote:
On Fri, 23 Apr 2021 15:12:15 -0700 (PDT), Chade


This is standard first call with a saw that has become difficult to
start, most often the damage is on the hot exhaust gas side and you can
see there the aluminium has smeared on the ring.

It was ok starting just overheated and cut out after a few minutes work. There were some scratches to be seen on the piston and cylinder but I would not say anything had smeared.

Just for the S&G's I put a new ring in a blower that had broken it's
ring and scratched the bore and whilst it did actually run, it didn't
run well (unsurprisingly). ;-)

Cheers, T i m

With Nikasil lined cylinders it is unusual for the bore to get scratched
from seizing or "nipping up" unless a hard foreign object has been
ingested. What normally happens id the aluminium piston overheats and
partially melts, not only jamming the ring in the piston lands so it can
no longer spring out and make a seal but also the bore picks up some
aluminium. Often you can get away with replacing the piston and ring but
you must remove the aluminium pick up in the bore, both chemically and
followed by a light hone.