andyrv6av8r

I'm having problems with my first gas motor. I bought and converted a Ryobi 31cc and installed it on a Giant Ugly Stick using Wacker Engines muffler, mount, and hub. Engine came with a Walbro WT 682 carb. The engine starts and runs great sitting on the ground; tilting the plane to the verticle position the engine dies quickly. I have had the fuel tank out 3 times to look for air leaks. I used new tubing and wrapped .020 safety wire around the tube fittings to prevent any slippage. I have tried the standard clunk as well as a filter/clunk unit like what came in the weedeater. No luck. This past weekend I purchased a Walbro WT324 to try, hoping it would work and I would have both low and high adjustments. Not only does the engine still die, it will not rev over half throttle. It appears to be running too lean. I have screwed both needles valves nearly completely out after starting at 2 turns each. Does anyone have any suggestions or thoughts as to my problem and which carb I should use if I can get this thing to run? Thanks

JohnF

Sounds like your fuel tank is not vented correctly. If you read through the "conversion" thread's I'm sure you'll find your answer.

warbird72

My Feedback: (79)

yes I agree with John it sounds like it's not vented right. I have converted several of these engines and never had one fail yet. If you give me a call I can give you some pointers and how to's Ernie.

Charley

My Feedback: (2)

Maybe the pulse passage to the carb is partially blocked or leaking, so the pump isn't providing enough fuel.

CR

mikenlapaz

andy Check this Walbro site http://wem.walbro.com/walbro/product...m=WT%2D682%2D1
It reflects the same venturi size and it also seems to indicate that carb does not have Needle valves #50 and #40.

Look for air leak either on case or carb mount. With it running brush some soapy water on suspect areas and see if you can get any bubles.

pe reivers

With the engine running horizontally, and not vertically, there's two things to check.

first pressure check the total fuel suction line while connected to the carb. There may be no leaks
second, Like already said: check the fuel fumping system. The pulse hole passage must be open, and line up with the carb pulse hole. The gasket must seal tha carb to the manifold. Do not use gasket goo of any kind. That will block the pulse hole.

Ryobi Coyote

Usually, an engine with blocked crankcase impulse air will be very difficult to start, or, more likely, will not start at all. (Without impulse air the carb will not pump or prime.) You may want to check it, but since yours starts I don't think that's your problem.

When you tilt vertically, do you see air bubbles in the fuel line? Does your Ryobi quit instantly or drop Rs and then quit?

Some years back, a buddy had the same problem. Everyone got into the act, looking for a carb problem. I stumbled along after they had given up, and they said “You fix it!” The clue was that the engine quit instantly. I figured it was not a carb problem because: 1. The crew had already gone over that a dozen different ways, and 2. With a fuel-draw problem, the engine RPM usually drops off, at least a little, before the engine quits. His died instantly. The trouble was that the wire from the mag to the kill switch had rubbed bare, and when the plane was tilted up, the wire touched against the cylinder, grounding the mag and killing the engine. This probably isn't your problem, but it shows how thinking ouside the box sometimes pays off.

R.C.

Antique

My Feedback: (4)

Pulse air has nothing to do with choking, it takes over after the engine is running..The tip here is if the engine starts when choked but stops after a few seconds when that fuel is used...If you completely close off the carb opening the suction from the piston going up pulls fuel through the inlet needle..You can sometimes look in the hole in the steel cover on the carb and see the diaphragm being pulled down when cranking...After it starts the pulse operates the pump function and keeps the carb full of fuel..

Charley

My Feedback: (2)

Is that entirely right? Pump has to get the fuel to the carb, choking makes the carb flow more fuel than nomal into engine, eh?

CR

Antique

My Feedback: (4)

Fuel will be pulled into the carb by choking even if the pulse hole is completely blocked..Cover up the pulse hole sometime and try it...Suction from the piston pulls fuel through the carb and into the engine...Air passing over the holes in the venturi pulls fuel from the chamber under the diaphragm when the engine is running...The pulse operates the pump to fill the chamber after it starts...
The carbs on our drone engines have no pump at all..Choke to start, crankcase pressure through a one way valve to the sealed gas tank pushes fuel into the chamber...Works great, better than the carbs with pumps...

Rcpilot

My Feedback: (78)

Check the carb size.

If you look in the choke or inlet side of any Walbro carb, you should be able to see a little number cast into the venturi. This number is read in 64ths of an inch. For example: 32 would indicate a venturi size of 32/64ths--or 1/2" A 28 would indicate 28/64ths of an inch. Or about 7/16"

On a stock Ryobi you want about 9mm or 11mm size venturi. We all know an inch is almost 25mm--so do the math. For an 11mm venturi--you'll need about a 30/64th carb or for a 9mm venturi you'll need something like a 22/64ths.

Now, what is the venturi size of your carb? You replaced the stock carb with a WT324--lok down the throat and look for the cast number in the venturi. What is it?

If your carb is too big--you will experience erratic engine behavior. I put too much carb on a Ryobi once. It runs okay up to about 1/2 throttle. These carbs run on the low speed needle up to about 1/2 throttle--then the high speed needle kicks in. When the carb is too big--it runs okay up to about 1/2 throttle because it's on the low speed needle. As soon as it starts to really suck fuel and transition into the high speed needle----it's INSTANTLY flooded. It's like flipping a switch. BANG--it shuts off. It will start right back up and run up to 1/2 throttle--no problem. But as soon as it starts to transition onto the high speed needle it will die.

Just a shot in the dark. You say it sounds lean. It can be pretty deceptive if the carb is too big. Look at the venturi and identify the carb size before we go any further. Lets at least determine if you have the right SIZE carb on this motor first.

pe reivers

I had a #28 venturi on my Ryobi, but also opened up the reed induction system, which is limiting the power in it's standard form. In the rotary inlet version, I used a #32 venturi. In my book, a #24 venturi carb is the best you can do on that engine if you do not plan further modifications.
Also check if the engine will go beyond 7000 rpm. Late type ignitions are limited to that rpm.

Ryobi Coyote

Don't think I said anything about choking. Read the post previous to mine. What I said was that if the engine runs, the impulse air must be getting to the carb. Even so, my experience is contrary to yours - even using an electric starter, stock Ryobis would not start if the carb wasn't getting impulse air. At least two of the "junkers" I "stole" at garage sales, didn't run because a saturday mechanic had blocked the impulse hole with Permatex or a cocked gasket.

However, we're getting off the thread's question: What is causing this Ryobi to quit when tilted up?

R.C.

captinjohn

It could be a loose fuel connection someplace. The extra suction needed to draw fuel up farther could be causing a air leak at a connection. Watch your fuel line real close and see if bubbles appear in it. Capt,n P.S. If that ,s not it I will think of another cause

Ryobi Coyote

CaptinJohn, Andy really has my attention here. As a Ryobi nut, I'd like to know what he finds is causing the engine to quit. Walbro-carbed 2-strokes are supposed to operate in any position. Other than my ideas above, I stumped.[sm=spinnyeyes.gif] Hmmm, what else could it be? Let-a-me tink!

R.C.

captinjohn

Not may people I know tilt a gas engine strait up to check its running. If this engine is at a slow idle...fuel that has puddled in crankcase could cause this, when tilted strait up. If engine was running wide open at full RPM... then it must have something to do with leaks or fuel draw. Capt,n

BillS

Quick death might indicate the fire is going out. You could put the timing light on it while someone else turns the airplane to vertical to isolate fire or fuel. It does not take much bump or pressure to cause one of the kill switches or coil to connect or disconnect.

Bill

Ryobi Coyote

Andy graciously agreed to send his engine to me, a complete stranger, for a look-see.

There’s an old saying that there are no dumb questions, only dumb answers. I can only say that Andy’s initial question, on this thread, really gave me and some other “motorheads” something to think about. Andy and I are now almost certain as to what caused his Ryobi to quit, but I must confess that the path from there to here was not a straight one.


The first thing I noticed, when I received the engine, was that something just didn’t look right with the fuel inlet – it appeared that the fuel inlet and the primer inlet were reversed. My procedure is not to disturb ANYTHING until I’ve seen the trouble. So I left things as they were. But the engine would not even start. So I tried reversing the inlets and still could not get’er to run. This had nothing to do with Andy’s problem; they were caused by the cold. In my garage, the temp was 10 degrees F(-12C), and with the door up the wind chill was -15F(-26C). The engine, the ten-year old batteries in my starter box, and Ryobi Coyote’s old body didn’t like this scene. A few days later, with new batteries and slightly-warmer temps, she started right up, and when the lines were reversed, BINGO, she leaned out and just quit, when I tilted her up!

Of course, there’s more to the story. Andy had tried replacing the OEM, single-needle carb with a two-needle carb (the one on the engine when I got it), and he says he tried reversing the inlets. None of these fixes seemed to help. Then there are the issues raised by RCIGN1 and pe reivers. From my experiences here, their posts (above) deserve some further consideration.

They say you can’t teach an old dog new tricks. Well, I’m an old dog and I not only learn new tricks, I also re-learn some old ones!

Andy has his engine back and says it's working fine.

R.C.

foamcut

My Feedback: (40)

I always learn something from the troubleshooting threads I read here...

andyrv6av8r

Thanks a million to John in solving my Ryobi problem. He went more than out of his way to help me solve this mystery of mine. The engine was flown twice yesterday and runs great! As to why I couldn't initially run the engine with the inlet line reversed, I suppose I will never know. I guess the old saying " You live and you learn " is true. Hat's off to one of the nicest gentleman I have ever met in this sport! Thanks again John! If you ever make it down this far South, I owe you!