rtstestpilot

My Feedback: (2)

Hi everyone. I have a ryobi 31 cc that runs strong for about 12 or so minutes. It starts easy and transitions very smoothly with plenty of power. Here.s the problem: after about 12 or so minutes of running, it will falter like it is runing out of fuel for a few minutes then die. I have had to dead stick this thing a few times and you can tell when it is getting ready to die due to the faltering. Once it dies, I can't get it started again until it cools. If you try to start it when it is still warm, you can see that there is air in the fuel line and the carb will not pull the fuel back to the carb unless you fully choke it. Sometimes you can get it to run fully choked but there is no power obviously and as soon as you try to throttle up or open the choke it will die. I can either let it cool down or wait till the next day and it will start the whole scenario over again. It acts like it is letting air back through the carb. once the engine gets warm. Also, it didn't use to do this. I have flown around 4 or 5 hours of actual flying time before it started behaving this way. There are no holes or air leaks coming grom the tank on to the carb. Any help would GREATLY be appreciated. Thanks, Todd

JohnF

Sounds like you are picking up some dirt in the fuel line or passage somehow. Once there is no draw from the pump the dirt might settle or disolve. Could be that something is going on with your vent line to the tank also?

av8tor1977

My Feedback: (6)

Yeah, I would be looking hard for a venting problem from the tank. Also clean the screen inside the carb. (It is under the fuel pump cover.)

AV8TOR

rtstestpilot

My Feedback: (2)

I'm pretty sure that it isn't tank oriented. The vent line is definitely clear and functioning properly. After it gets warm and starts acting up, it draws air in at the carb and lets the fuel siphon back into the tank. It acts as if something is warping once it is warm allowing air in. With the exception of the front seal, the plastic back case and the joint where the carb screw on are the only two places to draw air. I'm pretty sure it isn't the back plate because it is well gasketed and has the aluminum mounting plate that fully covers and compresses the plastic plate to the aluminum case. I'm guessing that is is either in the carb or at the joint where it screws on. Why would it run like the proverbial striped *** ape for 12 or so minutes before acting up and when allowed to cool down, run well again repeating the whole process? Thanks guys, Todd

Flathead

My Feedback: (11)

You might consider the 'Reed valve". Sometimes they heat up and pull away from the body of the venturi tube. After cooling they usually go back to working ok. It may also be getting some dirt under the valve. Pull the back of the engine off and double check the valve for seal and tension. Hope this works faor you, it sis for me. Flathead 4

deadcell

If your running the stock ignition, maybe your mag could be getting hot and breaking down???
How long do you have to wait for the engine to cool down before it will start again???
If its a long time, the next time it quits, spray some contact cleaner on the mag pickup unit and this should cool it down alot quicker.
Then see if it starts right back up or has to cool further, if its your reed valve it will not start until the inside of the block starts to cool.

frenchie79

At first thought your carb may be getting hot and Vapor loc, but you do have the plastic between the carb and engine. I would say your Magneto. Swap it if you have access to another Mag. Time a dozen at any repair shop.

rtstestpilot

My Feedback: (2)

I really think it is in the carb. or backplate assembly. I don't have a floor in the cockpit and I am using the clear yellow tygon tubing for the fuel line. When it acts up, you can see the fuel draining back into the tank. Actual "large" air bubbles headed back to the tank just like if you were opening a petcock at the carb. If you choke the engine fully it will sometimes draw hard enough to pull the fuel back up and run very poorly ( can't advance the throttle or open the choke back up or it will die). I've taken it apart and cleaned everything spotlessly including turning the reed valve over the one time I dismantled and rebuild the engine and back again the second time with no difference. It still ran very well till it got warm (usually around 12 or so minutes) then sputtered, quit, and wouldn't restart till it cooled down. I've been able to restart it within a couple of hours after it quit. Something is warping or failing once it gets warm but returns once it cools down. The thing is that it used to run very well (just like when you first start it now) all the time. I really appreciate all the input!! Thanks again, Todd

T.L.A.R. eng

Right after it stops, take the fuel tank cap off and see if it will draw fuel and start. Plug in a different tank while the condition is present. This will totaly eliminate the tank and plumbing.
It will be a process of elimination, usually it will turn out to be something very simple.
Just my .02$

Ralphbf

My Feedback: (27)

I also say venting problem.

Please discribe the plumbing of the fuel tank.

rtstestpilot

My Feedback: (2)

clunk line to carb., vent line out of tank with one wrap around tank and exit out of bottom of fuse. The fill line (3rd.) line is opposite of the vent line in that it is brass tubing that immediately curves downward inside the tank to just of the bottom of the tank floor. It can't interfere with the tank line this way and simply tip plane forward onto nose cowl to completely empty the tank. All lines are not blocked in the least amount and when pressure tested, hold for as long as one wants. This craft with this configuration has flown many hours before starting to act this way. I'm going to go out immediately to the shop and work on some projects. I will recheck everything I have stated here and rerun the engine till it either acts up or flys right. Sorry, I couldn't resist. I'll check back in this evening and if there is any change, I'll let everyone know. I really appreciate everyones help with this. Todd

rtstestpilot

My Feedback: (2)

Well, problem fixed! The only bad thing is that I'm not sure exactly what the problem was. To make a long story short, I got really P***** off, robbed a carb off my weed eater, installed it, and now she runs great again. I swapped back to the original carb that was malfuntioning and once again, when she heated up, she would die just like before. Swapped back to the weed eater carb and ran 3 tanks of fuel without so much as a gurgle. Yes, this is all that I have been doing since this afternoon! The new carb stays since I don't need my weed eater very often. I have taken apart the screwed up carb and still can't find anything wrong with it. I am going to buy a rebuild kit for it and try it again in the future but it will probably be put onto the weedeater. I'm going FLYING!!! Thanks everybody for all the input and when I actually find out exactly what went wrong with the carb, I'll let it be known. Todd

captinjohn

I just worked on a Ryobi for a friend. It seemd low on compression at first and could not hand start it. After some running and tunning the compression got better and it will hand start now also...but you have to have it tunned real good for hand starting. It had a kinda a unstable sound at full throttle. I put new tygon fuel line in complete install. I noticed little air bubbles in line after purge bulb. I removed that purge bulb completly and air bubbles dissapered and engine finally run even at full throttle. I do think the stock muffler should be gutted some for more RPM. It sure idles good and reves up very good and quick. Funny thing...not much vibes at idle and fairy smooth a top RPM, but has a nasty vibe about 1/4 wide open. Is this normal for a 31cc Ryobi? Thanks Capt,n[X(]

buck1856

My Feedback: (49)

Check the needle and seat.Under the cover with the 4 screws.Or its the pump membrane.Under the cover with 1 screw.