Thanks for the reply Checklst. I really find the RCU threads pertaining to engineering changes in engine designs as Ed Moorman brought out in his column in the RC Report December issue, and elsewhere, concerning the SK .90 engine being designed for low rpm's with high torque to be the most beneficial. Discussing engine break-in, and oil types to use is just hammering a subject matter that is already well established. As Ed mentioned, under propping the .90 engine can make the engine have problems at the higher rpm's. I have found my new SK .50's have a very tight pinch going through TDC, and thus used my heat gun to warm the cylinder before trying to make the first startup. While the engines became easier to hand prop after a few tanks of fuel(10% nitro & 25% all castor), they still have a tight pinch going through TDC. These engines seem to have very little break-in info in the box.

Rich S.