Stuffed saws/scored piston/barrel

Rob Chace

On lots of saws (and other 2t tools) i see with scored pistons and barrels etc
they have this sort of crystalised fuel/coke build up:

350-vertical-score

i have 2 440s and one had this inside the muffler alas not the other.
what causes this?

redmower

Robstar

I have a similar alteration to my stihl 880. The lad ran the saw on straight unleaded. Maybe something else is at play as well. The big saw was next to new.

I plan to fix it myself and learn a few things along the way. But have the mechanical skills of an earthworm so it sits beside my work bench waiting....

Rob Chace

i'm sort of mor einterested in the crystaline build up rather than the scored piston/barrel.

I would like to know what it is and what causes it.

Eric Frei

It's from high temperature, low quality two stroke oil, and too rich ..... carbonizes the oil in the gas mix.

A while back I ran out of 2-stroke oil and the nearest mower shop only had the husky 2-stroke oil. I used that in my Stihl.

The saw ran like shit and stank, you could feel pin heads of hot little pieces spitting out of the exhaust, like pinheads of molten sugar. I took the plug out and it too had little bits stuck to it. Of course the Husky folk reckon it was the good oil cleaning out the Stihl oils crap but I switched back to Stihl within a few days..... and use nothing else.

There are products around to de-coke the engine.

__________________

Drouin Tree Service

Ive been using a drum super TT,Its red oil and works well,The stihl oil is castrol.

__________________

Drouin Tree Services | Excavator Hire - Drouin and SE Gippsland | Landclearing Melbourne