The 58, 68 and 78 do fine on 15% nitro. However, the .40 and .48 have always performed best for me when run on 10% or less. I recommend using a fox idle bar glow plug with any fuel that contains a castor/syn mix.

Before you start you engine, make sure you seal up the engine. A little silicon on the carb retaining bolt, double check o-ring on carb to make sure it is in correct location and not pinched. Remove backplate and seal with w/ a little silicon RTV. Remove head and make sure it has a head gasket-some engines I've bought new to include non-MDS brands were missing a head gasket.

Using 15% and an 8 plug is too much timing advance due to the heat range of glow plug for the amount of nitro used for this engine.

Always run your engine slightly rich. MDS engines appear to be a little more sensitive to fuel tank height and carb mixtures. With fuel tank at no more than 1/4 full, start engine, go to full throttle and set mixture so that engine is 300 rpm shy of max lean rpm. Pinch fuel line briefly and release when engine is at full throttle (PINCH TEST) after mixture needle is adjusted to ensure that engine speeds up a bit (300 rpm) and then comes back down. Shut engine down and fill fuel tank to full and start engine. Engine will be slightly richer at full throttle than was set with 1/4 tank but this tuning setup will ensure that engine does not lean out as fuel level decreases (head pressure decreases).

Always do the pinch test at full throttle before every flight to ensure you are running several hundred rpms shy of max lean rpm. You WILL BE GUARANTEED the infamous MDS deadstick if you set your mixture too lean.

Good luck and don't worry. These are great engines. BTW, make sure you put at least 30 minutes of run time on your engine with mixture just pas the 4-2 stroke point at wide open throttle before you take her up. MDS engines, unlike OS engines, are Chrome plated, and need a lot longer to break in.