Question on Ryobi 33cc running

I recently converted a weedeater Ryobi 33cc to an airplane engine. The
conversion went smoothly and it started and ran (past tense) like a charm.
After about one hour of accumulated time on the test bench (32:1 break-in
mixture) it now will only run at half choke at full throttle!! It dies at
no choke but I can throttle it down. When I go from half choke to no choke,
it revs up to about 6,200 RPM (on a 18x10 Zinger) and then dies out. This
model Ryobi has only one needle valve for the high speed mixture. I have
adjusted it to no end and still get the same die off.
I'm pretty sure it is a fuel problem but I'm afraid to tear into the Walbro
carb. Any suggestions?
Reply to
Marlowe
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Do a Deja searcjh for my thread "Zenoah G-23 Help". Also my reply "Zenoah G-23 Help - Thanks" It was a similar problem. Rebuilding a Walbro-type carb is easy. Buy a reduild kit and take it slow when you open it. There are little parts that can easily get lost. Note which way things go before you take them apart. Be sure the filter screens are clean. Dirty gas is the bane of these engines. Dr.1 Driver "There's a Hun in the sun!"
Reply to
Dr1Driver
Good suggestion and a lot of info on your past thread, but most of it pertains to running too large a prop. I did learn a lot about fuel mixes though. I think your suggestion about disassembling the Walbro carb and cleaning is the possible solution. Do I need a rebuild kit just to clean it?
Reply to
Marlowe
Sound like a fuel starvation problem. I'd check the fuel delivery system from the tank to the needle assembly. It sounds like a clogged fuel screen or the needle jet has a blockage of some sort.
Jim W
Reply to
Black Cloud
Not unless you open and clean the filter screens. They are under soft metal covers that must be replaced with new ones when removed.
My problem was fuel draw related, too. It wouldn't draw enough fuel to pull the load I had on it. I removed the bronze filter from the tank, the Final Filter from the line, and the Dubro filler from the line. It picked up 200 RPM even on the too-large prop. As my chemical engineer wife reminded me; any resistance in the supply line, including sharp bends, increases the pressure drop
. Dr.1 Driver "There's a Hun in the sun!"
Reply to
Dr1Driver
Thanks for all the good suggestions from DR and BC. As suspected it was a fuel problem. I took off the cover to the Walbro carb and discovered that the fuel screen had a lot of crap in it. I cleaned it out and then blew air through the lines and the needle valve port. I then went to my tank and found the rubber stopper was dissolving from the gas environment! What kind of tanks are you suppose to use for gas? I then hastily built a tank from a small plastic water bottle and within minutes I had the Ryobi purring like a kitten. Top RPM 6,300 and idle 2,500 RPM on an 18x10 prop. Back to its old sweet self.
In addition to my question about tank type, what about an inline fuel filter? I have one for my glow engine and I will check if it is metal with no internal rubber. And how about the sintered clunk? Oh little grasshopper, there is so much to learn.
Reply to
Marlowe
Tear into it rebuild it....make sure you remove any welch plugs and after removal soak and clean the pi%@ out of it then put the new kit in; otherwise if you just throw a rebuild kit in it your wasting your money and time. Check the "pop off" and adjust for performance.
Good luck Mike
Reply to
Mike R.
Check with the LHS for a stopper made for Gas and also line for gas The gas will dissolve the lines used for glow fuel as well
Reply to
Steve
Mike thanks for the info, but you lost me on some of the terminology. Welch plugs and pop off are parts I'm not familiar with. We have our monthly R/C club meeting this Friday and we have some members who are gas knowledgeable, so I will be asking them many questions. If you see my earlier reply, you will note that I did a quick and dirty (bad choice of words) carb and fuel system cleanup and now its humming. I do want to be more gas savvy so that I can overhaul the Walbro carb in the future.
My next project is building a PIC based electronic CDI ignition. I've got all the hardware together and tonight I start on the software.
Reply to
Marlowe
Thanks for all the good suggestions from DR and BC. As suspected it was a fuel problem. I took off the cover to the Walbro carb and discovered that the fuel screen had a lot of crap in it. I cleaned it out and then blew air through the lines and the needle valve port. I then went to my tank and found the rubber stopper was dissolving from the gas environment! What kind of tanks are you suppose to use for gas? I then hastily built a tank from a small plastic water bottle and within minutes I had the Ryobi purring like a kitten. Top RPM 6,300 and idle 2,500 RPM on an 18x10 prop. Back to its old sweet self.
In addition to my question about tank type, what about an inline fuel filter? I have one for my glow engine and I will check if it is metal with no internal rubber. And how about the sintered clunk? Oh little grasshopper, there is so much to learn. ==================================== Some tanks come with a stopper that's supposed to be compatible with glow fuel or gas; others require you to buy a gas stopper. Here's a link to tanks on Tower's site
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Find the brand/size/shape you're interested in. The part notes will tell you if a special stopper is needed.
Fuel tank stoppers
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Reply to
Carrell
knowledgeable,
#1. Keep us apraised of the results of your CDI system. Be aware the C&H Ignitions are sold for that very engine.
#2. Get some Tygon line for your gas and a gas stopper (Dubro makes a change out gas stopper that will need a clunk [sintered bronze]) for gas. Silicon will melt and the junk that 'weeps' off it may be part of what is giving you a problem with the carb.
Reply to
Six_O'Clock_High
You need a standard tank with a "gas" neoprene stopper. This is black rubber, not grey or brown like glow stoppers. Dr.1 Driver "There's a Hun in the sun!"
Reply to
Dr1Driver
I took everything out of the gas supply line on my plane. I filter the gas twice coming out of the supply can, so it's clean when it goes into the tank. Dr.1 Driver "There's a Hun in the sun!"
Reply to
Dr1Driver
The welch plugs are small round covers with either an indentation or slight bulge made from alum,steel or brass. When the manufacturere has to drill a passageway connecting another on the outside of the carb or in he has to cover that hole.....so he uses welch plugs. "pop off" is the measurement in psi that the inlet needle will open. Check out some small engine supply companies.....they have special tools for removal of welch plugs and checking "pop off"....there not expensive.
Feel free to email if you need any more info Mike
Reply to
Mike R.
You may have your problem come back to haunt you: When you blew air into carb to clean it its possible that some trapped dirt may have worked its way up into a chamber just below a welch plug. This dirt will lay there and depending if the passage is for metering fuel/air the dirt can work its way back into that passage. You would not want this to happen when your plane is in the air. I would say you have a 50/50 chance of nothing or something bad happening. When you give a carb a thorough rebuild; you remove the welch plugs and replace them with new ones. Now you have 100% in your favor of nothing bad happening. I replied on your other post explaining about welch plugs. I dont want to scare you, but just trying to help you. I have been in the small engine service feild for 15 yrs and I am wroking at cemetery maintaining there equipment....also digging graves, trmming, cutting, ect, ect ,ect.... Out of those 15 yrs 4 yrs I raced go-karts (yamaha kt100s/ yamaha heavy class).....I learned from the best and did my own engine work......have a nice trophy collection and among those trophies I have my championship points trophy ( stroking the ego alittle :-) ).....so i know what I am doing. Please feel free to email if you need any further help.
Good luck Mike
A grasshopper???? Are you teathering that plane down at the feild like the fullsize at the airport??? :-)
Reply to
Mike R.

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