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I have a 2 stroke paramotor:

paramotor engine with parrot Paramotor with a parrot on the propeller.

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:

  1. 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.
  2. 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:

  1. the oil is only mixed at a 1:40 ratio, which is immensely low, just 2.5% of the fuel makeup.
  2. 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?

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  • Husquvarna do high revving 2 strokes so try the oil they supply , but quality comes at a price - which you may not like given you choose a no-name brand.
    – Solar Mike
    Nov 30, 2021 at 20:19
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    Did the loss of power happen before the carb tune-up, or after?
    – Weather Vane
    Nov 30, 2021 at 22:08
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    I don't think intuition is a good method to decide if the oil ration is optimal ( "1;40 is too low").
    – blacksmith37
    Dec 2, 2021 at 16:28
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    According to the EOS manual, semi or full synthetic oil is recommended. Using regular 2-stroke non synthetic oil may be the reason for the black goo collecting. For flying, an engine suddenly dying is not good for the life of the person flying. On the ground, using non recommended oil in chain saws, leaf blowers, etc may result in premature engine wear but doesn't endanger anyone on the ground. Either stick to recommended 2-stroke oil or anticipate premature wear and loss of engine performance if it hasn't already occurred. Synthetic oil is superior in specific applications like paramotors.
    – F Dryer
    Dec 3, 2021 at 20:30
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    Yes, I'm aware of your sport. As a student pilot flying with a large propeller overhead, I tend to follow procedures no matter how anal they are as it instills discipline. Occasionally, I add engine oil during my preflight and get hands dirty touching/feeling things. A loose lockout was found, delayed my flight until all the instructors came out, deliberated then called the flight school owner (licensed AMT) to simply tighten the lockout and let me fly. As owner operator, you're in control of your destiny so more responsibility falls on your shoulders to make the right choices and decisions.
    – F Dryer
    Dec 3, 2021 at 21:15

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First of all, excuse my English and my low ratio to make this answer a comment.

Secondly, I have always had the same doubt about how oil mixture affects 2stroke engine performance, and (I know it's not the same but...) few months ago I found an article wich is very interesting, talking about oil in chainsaws HERE

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