Hey guys, been reading this a bit, so when I was on the phone this morning with a fella that worked for a major two stroke manufacturer doing R&D on engines. So I asked him the balance question. Contrary to what I had thought, he told me that the whole assembly in its entirety is balanced. He also said their is a small amount of wiggle room of tolerance that an engine will take being out of balance. Boring out engines with standard weight pistons would stay together at about .050" overbore, after that they usually broke rods at high RPM. Also vibration increased the larger they went. Above the .050" overbore the crankshaft would have to be rebalanced to keep it running long enough for testing. They also tried other manufacturers pistons in their twin cylinder engines and said both had to be used as no two manufacturers had the exact same weight piston. When asked about a 2mm big bore kit for a saw, he figured that must be a lightened piston to get close to the range of its 2mm smaller counterpart. Then the conversation turned to different subjects.
For myself I would be curious if this were to be true, would like to weigh a piston from a big bore kit and compare to a standard one and see how this shakes out. Interesting subject to be sure, for a side note those engines he worked on were anywhere form 250cc to 440cc singles and twins, so some interpretation is needed in the translation to a saw that is say 35cc to 100cc. My guess is the smaller the engine, the smaller the weight change the more tolerated by said engine. Then again WTF do I know about it.LOL
Hope this helps shed light on this for some of you and not muddy the waters further as it is not my intention to, really, it's not...
