George McCoy

Hi Karl and Charles

Careful with adding more oil to the premix thinking it may help lubricate better.  The premix will become more viscous (thicker) and will not flow through the fixed size super small jet orifices in the carburator as easily and the saw may run very lean and sieze.   The real enemy is correct air-fuel ratio with saws as a lean mix will sieze a saw in minutes due to piston expansion (unradiated and scavenged heat).

Imagine a ratio of 1:1 super think mixture and how it might struggle to flow through a small hole just a few thousanths of an inch diamter (jet).  Now imagine a ratio of 100:1 and how thin it is and easy to flow like water.  Hence, a higher ratio of 50:1 will flow more 'fluid' and carry more oil into the combustion process than a 40:1.  i.e. a 50:1 will run rich and a 40:1 will run lean given the same metering needle position and fixed jet size.

The above is based on years of racing 2 stroke motorcycles with very high RPM engines, including Husqvarna, back in the 60's and 70's !

I've used a synthetic racing oil BelRay MC1 for high RPM racing engines in all my saws at 50:1 for the past 30 years.  I just put a ring on my 359 after more than 125 cords of wood and I didn't need the new ring, piston still looked new except slight carbon on top and cylinder still had original 140* inclusive angle cross hatch hone marks from the factory back in 2004.  I opened it up just for fun, not to solve a problem since it just keeps running stronger than my pal's MS 440 Stihl and I wanted to learn why.

Cheers

George