Ryobi 4 cycle
06-20-2003 | 04:25 PM
#1
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From: San Diego, California
Ryobi 4 cycle
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.
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.
06-20-2003 | 09:33 PM
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From: N.E. OREGON
Ryobi 4 cycle
Robert,
You must be running the Gen. 1 engine with the aluminum pan. Most people on this site say their Ryobi's came with a 7.5mm carb which leads me to believe that they all are using the first generation of engine. Gen. 2 has a plastic engine pan and a 9mm WYL. The stock jet is a 35. I put in a 46 from another carb but that is too much fuel. Also, I've been told that the WT456 carb is a dual needle number that came on the Gen. 1 engines and will work.
Do you get a surging in your idle and top end rpm? Mine fluctuates up to 300 rpm with the stock carb when idling and full throttle. My guess is that the removal of intake and exhaust restrictions have excessively leaned the mixtures. I'm thinking the adjustable needles on the WT456 carb should stop that.
Keep us posted on any new findings with this engine. A friend of mine has a boring bar and honing machine and I may try to punch it out if possible.
You must be running the Gen. 1 engine with the aluminum pan. Most people on this site say their Ryobi's came with a 7.5mm carb which leads me to believe that they all are using the first generation of engine. Gen. 2 has a plastic engine pan and a 9mm WYL. The stock jet is a 35. I put in a 46 from another carb but that is too much fuel. Also, I've been told that the WT456 carb is a dual needle number that came on the Gen. 1 engines and will work.
Do you get a surging in your idle and top end rpm? Mine fluctuates up to 300 rpm with the stock carb when idling and full throttle. My guess is that the removal of intake and exhaust restrictions have excessively leaned the mixtures. I'm thinking the adjustable needles on the WT456 carb should stop that.
Keep us posted on any new findings with this engine. A friend of mine has a boring bar and honing machine and I may try to punch it out if possible.
01-27-2007 | 09:39 PM
#5
RE: Ryobi 4 cycle
Have you Guys seen the 29cc 4 cycle engine on a Trimmer sold at Lows? Looks nice. You can take the oil plug out and peek in and see crankshaft and ball bearings. Capt,n
