I have a 2 stroke paramotor:
It is a 235cc 2-stroke engine with carburetor fuel delivery and magneto ignition. The transmission is a direct drive pulley system. As a normal part of the 2-stroke fuel, I mix in oil at the manufacturer's suggested 40:1 ratio. I recently found that the power delivered by the paramotor is very low. the top of the power band for this engine is 8,000 RPM according to the manufacturer, and with this propeller, the engine will normally readily spin to 7200 RPM (Propeller max. RPM). The engine now only spins to 6000 RPM under max throttle. I've had the idea that the oil fuel additive could make a power difference. I use a no-name two stroke oil made for engines smaller than mine.
Why do I think that the oil could be the problem:
- until the exhaust is very hot, a sticky tar substance will leak from the joints. it is solid at room-temp and will become soft if I hit it with my heat gun. I suspect that the internals are becoming dirty.
- The oil is obviously not made for paramotors (though there is currently NO oil made commercially for paramotors specifically). But it is also not made for performance engines.
Why do I think that this could not be the oil:
- the oil is only mixed at a 1:40 ratio, which is immensely low, just 2.5% of the fuel makeup.
- the carburetor was just re-tuned.
Could the oil I add to the fuel at this ratio make the difference between 6000 and 7200 RPM?