I have an SK 80 ,Read the instructions that came in the box for tunning. I used the pinch method at full throttle to break it in while using ear protection of course. Go to full throttle with a 12*6 keep it rich say 4 or 5 clicks out from top rpm. pinch the hose to get to the high rpm and let it go. This heats up the cylinder for a period and then cools it down with lots of oil. Do this over and over for a full 10 oz tank. After the break in is done you should switch to a 13 *6 or 13*8 I used both. Tune the high end with the bigger prop and go into rich land with 1 or 2 clicks out. The real work is now setting the low rpm mixture. I recommend taking your time with it. Start by setting it to the factory spec. !QUOT! Step 5 !QUOT! screw all the way in to a gentle stop and screw out 1.5 turns. Start the engine and screw in 1/4 turn or less for each run until the goal of perfect throttle response from idle to full is realized. In my case the low mix was too rich a it cost a couple of glow plugs. I have found that the best plug for the engine is an A3 from OS which is generally used for smaller engines around 25 to 15 or so. I also removed one shim ran 5 % nitro and never had a flame out again. Depending on your skill you may want to stick with 10% and not remove a shim. Do not continue to run high nitro as this engine doesn't respond well to it. Good luck this is a great engine for theses who are willing to work em.

Mine flys my TF P39 over 80mph also it unloads in the sky and really rips.
Eric