Poulan Pro P3314 scored piston: help me understand why this causes problems

[ILENGINE]

Just to remind those who own any 2 stroke equipment. Don't loan out your equipment.
Follow the fuel mix recommendation.
That particular saw used 40:1 or 32:1 mix. Keep your mix separate from your non-mix gas.

The started out as a 40:1 saw but sometime in the works without telling anybody they changed them to 50:1. Want to see something interesting, go look at a can of Poulan Pro pre-mixed gas. It list 40:1 and 50:1 on the same can.

 

[Forest#2]

Summary: (from Poulan experience)

After working on that type saw you will then be able to recognize a better built saw when you see one.

You are getting chainsaw experience and that is best type to get chainsaw experience. Poulan (for occasional USE only) This is on the FRONT page of the owners manual.

Buying new parts for that type saw will result in having more in it than it's worth NEW.
Also you will find that other saws with the same model number WILL HAVE parts that are not interchangable, especially on the power head. (type 1, 2, 3 4 etc and even then within these parts not interchange).
I have a salvage with donor Poulans and take sometimes 3 or 4 and repair one. (and then use it as a loaner saw)

If your compression gauge is correct the 70-120 is too low to get a good run and usually hard starting. That saw would normally have 140 and up.
You need to check your gauge on a good engine. It's also quite common for small engine 2 cycle gauges to not read correct. (usually they read low and can mis-lead a mechanic)

I would set it back and watch yard sales and trash dumps and if you want to work on Poulans for 2 cycle chainsaw experience, use the others as donors.

Saw was probably overworked (not occasionally used, means light duty and let it rest quite often) and maybe running lean, or carbon build-up from too much oil in the mix,
no or dirty air filter.

 

[MParr]

The started out as a 40:1 saw but sometime in the works without telling anybody they changed them to 50:1. Want to see something interesting, go look at a can of Poulan Pro pre-mixed gas. It list 40:1 and 50:1 on the same can.

I have an old 16" Poulan Pro saw. It's not the green color, it's the school bus yellow and black. I've always run 40:1 mix in it. It's been a great little saw. I've only had to replace a coil, primer bulb, fuel lines. Of course, the usual plugs and air filters. I've never loaned it out and I always dump the mix and burn up any leftover mix before putting it up.

 

[hlw49]

With scoring on the rings piston and cylinder the engine is not creating enough vacuum in the crank case to pull in the proper amount of fuel mix into the crank case to start and run properly. Blow by the scoring is putting pressure into the crankcase.