Ported STIHL 021 stress test.

The 021 project saw “Bob’s Saw” now ported with its new diy pipe, fitted with an 18” bar sporting 3/8LP full comp chain. After two tanks of fuel for brake in, ran limbing, it was time to do a stress test. Over all moving through this 27” dry hard maple was better than stock by far, I did manage to push a litttle too hard and bog the saw down to a chain stall at least once. While in no doubt this is cutting far better than the stock saw was, I’m not overly impressed and believe that I can do better. Post video, a cold compression reading of 92psi would agree. I’m amazed that the thing even runs this well with that figure. Looking over what I have done and how I can improve, im noticing that the exhaust opening at 90* atdc is likely the cause of low compression and low torque. Another cylinder has been obtained, along with a pop up piston, and another rotating assembly. The squish on this unit is also a large, 0.040” I am looking to cut that to 16-20 thousandths, possibly by flat sanding the base, and using emery around a mandrill to then raise the bearing and seal pockets. More to follow.

[@HayChaffandSawdust1]

I see, reading the description, you have bigger plans YET! She ain't a slouch right now, but I think you'll make it even better!!

[@Archer_82]

Sanding the bearing pockets now, I was at .028” for squish last measurement. I’m definitely interested in seeing what changes this makes to timing, compression, and smile factor.

[@HayChaffandSawdust1]

@@Archer_82 Ahhh the ole Smile Factor!! That, right THERE is the reason I can't run a stock saw... no teeth showing! Anxious to hear how it works out with the squish work... you will get a double whammy... you will gain some exhaust roof too. Anxious to hear how it works out whether it is success or ...that other thing.

[@Archer_82]

Appreciate the anticipation and kind words, from an actual saw builder. I’m also looking forward to finding if this does much, big win, or not much change, ether way, its experience gained for the next adventure.