ORIGINAL: bob27s
until not long ago, Horizon had the ASP line here in the USA.
It appears they only have a few parts left these days.
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Before that it was Jim Goad at Indy R/C.
I owned and ran/flew the very early ASP engines, from .12 to 1.08 in the early Nineties. I had zero problems with them and had lots of satisfaction. The trick was not to use more than 5% nitro in ASP engines and to make sure you had some castor oil in the fuel.