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Are/were your ST engines made in Italy or China?

Being of European origin, these engines were set up to use 0 - 5% nitro. Running them on higher nitro can require richening the high speed needle excessively, which richens the midrange too. So what do we have? An engine that has a proper high speed adjustment, but which now has a rich midrange.

Burn 5% nitro fuel and everything falls into place. Or, add a headshim to lower the compression, then the necessary high speed mixture will not cause an excessive midrange.

There used to be charts available showing just how much rpm gain that one could expect for each 5% increase in nitro content. Once studied and digested, it became clear that running more than 5% nitro in two-stroke engines designed for sport use was just flushing money down the toilet and creating mysterious carb problems for those not in the know.

Granted, you may find a day now and then when the weather is "just right" to permit your engine to enjoy a bit of a power boost and crisper handling by using more nitro, but on the average, more than 5% nitro for two-strokes causes more problems than it solves.

The ASP, MDS, Magnum, Royal and several other brands of yesteryear were set up for 0 -5% nitro. Each of these engines had terrible reputations for deadsticking, rich midrange running and several other symptoms that were worsened by using too much nitro in the fuel.

Duke Fox used to set up his engines to burn his Missile Mist fuel. They ran like crap on 5% nitro. Missile Mist contained a mix of 25% nitromethane and nitroethane. This required a low compression ratio. I had a phone conversation with Duke about this very subject in the late seventies. I asked him why he did this, knowing full well that he was trying to lock you into not only buying his engines, but his expensive fuel. His answer was nebulous and non informative. I knew why and so did he.

I told Duke that I had finally reached the point where crashing was a rare thing for me and that I often either sold or gave away old engines to folks that needed a helping hand. The point being, that I had finally reached enough proficiency to begin buying really expensive model engines, since I normally did not crash them. He asked me what my point was. I said that I was considering buying European pattern engines that would run fine on 0-5% nitro and save some money while doing my endless hours of pattern flying practice. I said that I would rather pay a little more for an engine that burned cheap fuel, than pay very little for an engine that burned expensive fuel. Six months later he introduced a low nitro replacement cylinder head for his Eagle .60. This is the pre schneurle ported engine. The head can be recognized by its vertical glow plug.

It used to be that increasing the nitro content of fuel cost the consumer a lot more money than it does today. However, money aside, many engines simply are not calibrated to run properly on more than 5% nitromethane. Four-strokes are mostly different in this regard. The HP drum valve engines are exceptions. They are set up to run on 0-5% nitro and will run terribly on higher nitro fuel.

Everyone has a crusade over one issue or another in life. This one is mine. Do yourself a favor and back off the nitro content when running two-strokes. You will be amazed to discover that the engine actually runs better, once you get the needles and glow plug choice straightened out.