I have two older K&B 40's which are very similar, but not exact. One runs like a top but is well worn, and uses a strap on muffler, the other one is mint, with a nice muffler, but has cracked piston rings. I want to average the the parts on the two engines to make one very nice one. Specifically, i want to take the piston and rings out of the running engine and put it in the broken one. can this be done without damage or bad performance? The carbs have already been swapped, and I have a new head to go on either one, So i want to make a nice engine out of my two older ones. Am i asking for trouble? Both motors have already been broken in.