572xp or MS500i

[Hermio]

You obviously haven't checked, squish, or port timing in a number of engines, or know how manufacturing goes. The fact is mass production parts have a set tolerance they have to meet. Sometimes the tolerances are at one the end of the spectrum, sometimes, the other end, and sometimes they're spot on. Cylinders, pistons and cases are rough castings, to get them finished, and within speck, they have to be machined. Sometimes these parts have to be machined to the far end of what's acceptable to prevent waste. This is what happens in mass production.

Now, if you were building an F1 engine or Nascar engine, this would not occur, those parts are discarded. These are chainsaws the tolerances are quite crude honestly. Some manufacturers have different tolerances allowed, check the radial crank runout on a Honda VS a Harley-Davidson.

True. I do not do mechanical work on engines. I used to work for a manufacturer of gear drives, and they practiced 100% inspection to their specified tolerances. With NC machining, they rarely were out of spec. If chainsaw tolerance bands allow a noticeable difference at the far ends of the spectrum, they are not a very precise product. I can understand such slippiness from Holtzforma, but I would expect better from Stihl or Husqvarna. BTW, are you sure pistons are castings? I thought they were forgings.

 

[ericm979]

The high silicon alloy needed to make two stroke pistons that do not expand too much from heat does not forge well. So the good two stroke pistons are cast.

I have run forged Wisecos in a race bike when I could not get OEM pistons in the right size. They needed much more clearance cold and were a bit noisy until the engine warmed up.

Production engines have tolerances on each part. The engines are designed so that they will still work correctly when the tolerances are at the ends of their ranges. For example Yamaha two strokes nearly always had too much squish clearance. That's because of the tolerance ranges on the cylinder,. cases, crank, con rod and piston could add up. If you get a short cylinder, tall piston and long rod on short cases you dont' want the piston to hit the head.

If it hasn't been pointed out already the injection system in the 500i has been available in cutoff saws for years. If it can handle that environment being in a saw should be easy.