Tmoth4

My Feedback: (1)

I have a frustrating problem with a Ryobi 31cc conversion. It ran great when it was a weedwhacker, but now it's almost impossiple to get it to run. It'll run on the prime but doesn't draw fuel through the feed line. I choke the carb with my finger and crank the prop through like I usually do before starting and no fuel draws through. I've checked everything many times, changed gaskets, used gasket sealer and taken the carb apart to check for clogs, etc. Nothing helps. It's not the fuel tank, because I ran another engine the same day using the same tank. Could it be a problem with the reed valve, or what?

kevin mcgrath

My Feedback: (1)

When you converted the engine from its former life what did you do about the priming bulb fitting?Some people retain the bulb but if you didnt the fitting on the carb must be plugged....As a weeder the engine uses a cheap rotating plate choke.....why didnt you retain it?It sure makes life easier than sticking your thumb in the carb.....

Tmoth4

My Feedback: (1)

Yes, I did plug the other fitting. I crimped the end of it and soldered the opening to make sure there was no air leak. When I disassembled the carb after trying to run the engine, I didn't see any gas inside at all. It was dry. Maybe I should have kept the choke, but I don't think that's the problem. It doesn't draw fuel even when it's running on the prime.

Tmoth4

My Feedback: (1)

Captinjohn,
How can you tell if the reed valve is good or not? And where can I get Walbro carbs? This Ryobi has a Zama carbureter, made in China, which looks like a copy of the Walbro, which has made in Mexico stamped on the bottom.

Flypaper 2

There,s a pulse hole in the crankcase where the carb bolts on. Make sure the hole in the plastic block lines up with this. Also make sure the hole lines on the other side of the plastic block lines up with the hole in the carb

I flunked my kamikazi pilots licence test !!

Tmoth4

My Feedback: (1)

I finally got it to draw fuel by taking the covers off the carb and wetting everything inside with gas. I actually got it to run for a while, but when I shut it off, I couldn't get it to start again. I tried to keep the pulse hole lined up, but maybe the reed valve isn't closing completely. The compression is awfully low. Would increasing the compression make it easier to start?

rctimm99

My Feedback: (34)

This engine is a low compression engine. It will gain compression when it runs (oil / gas).

You can replace the thick head gasget with a thinner one, but the gain is very small. The up side of this lower compression engine is you can start with a typical glow started. The big upsided is the cost is about 100 bucks converted.

The Zama carby locks up when dry. Bummer you took the primer bulb off. I have one that does exaclty what you are seeing.... just pour a bit of gas on the vent side of the diapham and you should start pumping again.

Tmoth4

My Feedback: (1)

It's frustrating. I got it to run for about 10 min straight. Nice and smooth with good transition from low to high throttle, but when I shut it off and tried to restart, it wouldn't pop or anything.
I wanted to use this engine on my 1/4 scale Tigermoth because of the narrow cowling, if only I could get it to start reliably. I have Homelites in other planes and they start real easy, but you have to cut a big hole in the cowling for the carb if it's a narrow nose.

Tmoth4

My Feedback: (1)

Captinjohn,
Engine was not hot. I ran it in 50 degree weather and I could touch the engine afterwards. I am hand flipping and using 32:1 gas, but it's been tried with a heavy duty starter with the same result. Your method of checking for leaks sounds good. I'll try it.
I just test ran a G62 right out of the box and it started so easy I felt like kissing it.

Jemo

My Feedback: (5)

Open the reed valve stop, so it allows the valve to open twice the amount of the stock setting. (i think 1/8')

Jemo

My Feedback: (5)

captinjack:
You don't need a better reed valve. If you havn't opened it yet then try it, you can always close it back to stock.
When I first tried my Ryobi, it was stock except for the carb. (the throat had been opened (easier to get a bigger carb).
I couldn't keep the engine running without choking it. After bending the valve stop, so it would open wider, the engine came alive and ran great.

tkg

My Feedback: (1)

There is a chance that your problem is not gas but spark. Losen the mag screws and set it as close as you can to the flywheel without it rubbing anyplace. This will give you spark at a lower speed.

Tmoth4

My Feedback: (1)

I'll try that. Thanks

rsrogers

My Feedback: (10)

Hey Guys! I convert homelights & ryobis and it sounds like to me that the carb might need a new diaphram on the pump side ( opposite the primer bulb). I could be wrong but every time I've had this kind of fuel problem thats where I start. If Im not mistaken , when you take the cap off the pump side the diaphram goes on the carb between the gasket and cap, if this is not correct the engine will starve. If you do get the engine running (pour gas in it) Vacuum from the cylinder is enough to keep it running. I know that if I go to an over size carb on these engines I put the diaphram on then the gasket & it usualy cuts the fuel down enough to keep it from flooding out & running rich. For the correct reed setting you should be able to get a 1/8 drill rod between the reed & reed stop. Hope I,ve helped.

Steve

Tmoth4

My Feedback: (1)

I opened the reed valve to about 1/8 in. I got it running for 10 min. straight with occasional goosing of the throttle and tweeking of the mixture. It ran fine, but when I shut it off I coudn't restart after a half hour of flipping and choking and flipping, etc. No pop or anything. I gave up and went to bed. Maybe I'll try again this weekend when my arm gets better.

w8ye

My Feedback: (16)

If the reed valves are sprung, the engine will only pop when brought past a compression stroke. It will not run on it's own.

Jim

flipflop

I'd been having trouble with my Ryobi conversion for the past month, it would run great for ten to twenty seconds, then start 4-cyclying. No amount of carb adjusting seemed to help, tried a different carb, still doing it. Then I remembered that I had opened the reed valve limiter a little. Close examination revealed that the reed was not completely closing any more. I rebent the reed limiter and it cured the problem. So if you've bent the reed limiter, view it from the side while holding it up to a light to make sure that your reed is closing completely. If it's not closing, hammer the section that holds the base of the reed flat, reassemble and check to make sure the reed is completely closed.

Tmoth4

My Feedback: (1)

Thanks,
This sounds like a good thing to check. The reed valve was one of the things I've been suspecting.

Flypaper 2

Put an automotive compression tester on it , if less than 75 lbs your wasting your time. Riobi is the lowest on the totem pole as far as quality goes. Irepair small motors for a living.

Tmoth4

My Feedback: (1)

Maybe that's the problem. I've had much better luck with Homelite conversions. The Ryobis, with the rear carb & exhaust, would be ideal for narrow cowled planes like the Chipmunk or Tigermoth. if only they were more reliable.

Flypaper 2

I've converted many Homelites, no problems. Homelite Super Mini, 30cc makes a nice conversion as the carb sits upright beside the cylinder for a narrow profile.

Tmoth4

My Feedback: (1)

I ended up using a Homelite 30cc on the Tigermoth. It flies the plane fine, but the carb sticks out quite a bit through the side of the cowl. It kind of ruins the looks of the plane on one side.
I never heard of the Super mini. What does this come in?

Flypaper 2

CaptinJohn

The Super Mini is an older Homelite from the 80s. Ihave a digital camera but can't get it to cooperate with the computer. I also have an old Super XL Homelite. 60cc on a Byron Christen Eagle. It has an old Tillotson carb with a diaphram accelerator pump on the side of it. Idles with complete 2 cycle all the time.

Tmoth4

My Feedback: (1)

I pulled the plug out of the Ryobi last night and tested the spark. It was very inconsistant. I narrowed the gap a little and got a consistant spark even when flipping slow. I also pulled the backplate off and looked at the reed valve from the side, and sure enough it wasn't sealing. I could see light through the space. I tried to run it and got consistant popping but no run. It acts like it wants to run, but I think I'll have to play with the reed valve more, and my mixtures might be out of whack from all my past efforts.
Thanks to everybody for their ideas. I think I'm getting closer now to getting this thing to run properly. I'm on a mission now.

tkg

My Feedback: (1)

Instead of bending the reed valve, see if you can just turn it over.