ORIGINAL: cutaway
Do you use an air filter?
I've noticed that car fuels tend to be lighter on oil content than a lot of airplane fuels. You might try using airplane fuel of modest nitro content (5-10%) with some castor oil in it. I've had airplane engines run for many hundreds of hours with low nitro fuels that had castor oil in them. The one's that have been whipped hard with 40% nitro in competition tended to wear out and break faster than the more conservatively run ones.
Any engine take a while to break in properly too. Even the supposedly ''quick'' breaking in ABC's can take 45 minutes or more of gentle treatment before they're really ready to flog hard. Rush the process and longevity and performance ultimately suffer.
I always run a air filter in all my aircraft. I use them on my 2 and 4 strokes. On my 2 strokes I run 10% and my 4 strokes I run on 15%. I bought a whole bunch of Bru Line Air Filters and Boots just when they became discontinued. I bought enough to last me for years and cleaned out my LHS when they had them. A engine is a engine no matter if it's a 4 stroke or 2. The only differences is the fuel and the 4 stroke has more moving parts. (Talking about theory, not design)
I don't know why some people don't use filters when most of us have found dead bugs, dirt, dust, sand and grass clippings on or around our aircraft. To me it's just plain obvious that it would be smart to slap on a air filter. Plus, I notice my engines last longer and run a little better with a air filter on it. And to top it all off, I always put on a fuel filter. Never know what junk from the bottom of the jug slips through the glow tank.
That's my take on it.
Pete