I have been corresponding with BobL on this subject the article that I have compiled is very large (64kbs) and on his advice I have posted the first paragraph and hopefully the rest as a pdf , Peter
FUEL FAILURES


Failures from stale fuel and fuel separation.
( This is an excerpt quoted directly from the Echo workshop repair manual )
“Using fresh petrol with a minimum octane rating of 89 through to 92 (mid-range to premium) at all times. The petrol manufacturers blend mid range and premium petrol with greater amounts of detergents and anti-oxidizing additives to “keep engines clean.” Lack of these detergents and additives in two stroke fuel will cause a heavy build up of varnish and gum deposits on the piston surface and ring grooves . Once the ring start sticking in the ring grooves ,exhaust gases will leak past them . This causes overheating of the piston , which in turn causes galling or seizures. Regular unleaded 87 octane petrol may not contain enough detergent additives that are need in an emission certified 2-stroke engine to keep varnish,gum and lacquer deposits from forming.


Attachment 100247