I converted a 26cc Ryobi 4 cycle three years ago and been flying ever since, I have leraned a great deal of experience with this engine - flying a 1/4 scale piper cub. I would like to share my experience with those of you interested.

Carburator:

To begin with the stock carburator you need to replace it with a larger venturi carb. The stock carb is 7.5 mm with a size 35 jet, you can change it to size 42 it will improve the lean setting problem past half throthle opening. The ultimate power performance is realized with a 9mm rotary barrel walbro wyl - 100.

Ignition:

I removed the magnet flywheel and installed CH electronic ignition, improved the performance at high end as well reduced the total weight to 56 oz.

Propeller:

Master airscrew classic series 16x8 @ 7500RPM , 1.57 hp, 9.82 lbs. thrust (best suited for cub).

Master airscrew classic 18x6 @ 7000RPM, 1.54 hp, 13.7lbs. thrust.

Master airscrew callsic 18x8 @ 6000Rpm, 1.29hp, 10 lbs thrust.


Engine orientation:

The engine is mounted inverted with the oil in cranckase on the top. Fill about 2.5 oz. oil if you have to mount it inverted, run a long tube from the cranckcase breather and coil it.

I have installed an oil drain plug under the crankcase, it allows me to change oil or add oil easily, were as the original drain plug is located between the firewall and engine cranckase, mounted in an angle and hard to reach.

Oil grade.

I have tryed syntetic grade and regular 30 weight motor oil, for inverted mounted engine I recommend 40 weight Chevron oil.

Gas.

I have been running it on coleman stove white gas $3.50 a gallon available at sporting stores.

Octane boosters or high octane does not do any good.

Conclusion:

Overall this engine with custom muffler sounds great in the air, easy starting, never had a dead stick experience. CERTAINLY NOT A POWER HOUSE.