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a mystery of a ryobi that won's start

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Old 05-19-2006, 01:02 PM
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sboxer
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Default a mystery of a ryobi that won's start

I purchased a beautifully converted short-shaft ryobi second hand that seems to be in great condition-but that I never saw run. Unfortunately, it will not start for me. Here are the symptoms:

It draws fuel with the throttle open and the choke on;
It will pop if I squirt some carb cleaner (ether) in the crankcase but the engine will not run for more than a few seconds;
I can get it to "run" with the choke fully on, but it runs very, very rich (so rich that the throttle does not change the speed of the engine;
I am using coleman fuel mixed 32:1 (which works just fine on my real weed wacker and homelite blower);
The carb diaphrams looks nice and clean to me;
I've tried resetting the spark plug gap and used several plugs;
I've reset magneto gap and I can see a nice spark with the plug out and grounded on the crankcase;
I'm using a standard starter w/ 19.2 volts that starts my other Ryobi conversion;
I've tried various needle settings, but I've test multiple times at settings between 1 and 2 turns.

OK conversion gurus...what gives and what should I look for?
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Old 05-19-2006, 02:11 PM
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Default RE: a mystery of a ryobi that won's start

Quote:
ORIGINAL: sboxer

I purchased a beautifully converted short-shaft ryobi second hand that seems to be in great condition-but that I never saw run. Unfortunately, it will not start for me. Here are the symptoms:

It draws fuel with the throttle open and the choke on;
It will pop if I squirt some carb cleaner (ether) in the crankcase but the engine will not run for more than a few seconds;
I can get it to "run" with the choke fully on, but it runs very, very rich (so rich that the throttle does not change the speed of the engine;
I am using coleman fuel mixed 32:1 (which works just fine on my real weed wacker and homelite blower);
The carb diaphrams looks nice and clean to me;
I've tried resetting the spark plug gap and used several plugs;
I've reset magneto gap and I can see a nice spark with the plug out and grounded on the crankcase;
I'm using a standard starter w/ 19.2 volts that starts my other Ryobi conversion;
I've tried various needle settings, but I've test multiple times at settings between 1 and 2 turns.

OK conversion gurus...what gives and what should I look for?
Well, you know it runs. You need 3 things to make it run well.
Air
Fuel
Spark

You got air and spark. You've already confirmed that. Only thing left is the fuel.

Swap the carb off another engine that runs good. If it makes the new engine run good--then you have determined that the carb is the culprit.

Buy a carb rebuild kit. Make sure you pop the welch plugs and check the screens to make sure they aren't clogged with crud. Don't just swap the diaphrams and the jet. You need to check those filter screens too.

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Old 05-19-2006, 06:40 PM
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Default RE: a mystery of a ryobi that won's start

That seems like a good place to go from here. I've have not rebuilt a card, so it should be interesting trying. My assumption was that since I could see gas pumping into the carb that it was actually getting into the crank.

Thanks for the quick reply and putting it in terms even I can undertand.
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Old 05-19-2006, 07:10 PM
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Default RE: a mystery of a ryobi that won's start

One other thing you need is compression. I agree with Rcpilot...could be some crud some place in that carburator. The screens do have to be clean to pass fuel good. Take Care Capt,n
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Old 05-20-2006, 08:31 AM
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Default RE: a mystery of a ryobi that won's start

Is the pulse hole for the pump aligned with the carb properly ?
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Old 05-20-2006, 10:08 AM
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Default RE: a mystery of a ryobi that won's start

I checked the screens in the carb and, from my limited experience, they look good. I also checked the pulse hole and confirmed that it is aligned with the carb/gaskets/carb spacer and back of the crankcase.

SB
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Old 05-20-2006, 11:34 AM
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Default RE: a mystery of a ryobi that won's start

Suggest you spray WD 40 in the throat of the carb and put the electric starter to it. The engine should pop and run for a few seconds if there is spark at approximately the correct time.

The problem needs diagnosing before changing parts.


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Old 05-20-2006, 06:36 PM
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Default RE: a mystery of a ryobi that won's start

You might need to take a look at that valve (for lack of a better discription) under the pump diaphram. I had to adjust mine to get it to run more reliable. Also, make sure the diaphram is not hard or stiff. It needs to be flexable to pump. The first time I tried to start mine in the plane I had to raise the tail to get fuel to flow. Only needed to do this on the first flight of the day. After that, it would start easily every time. Took a few days to run across that solution. Never did figure that one out.
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Old 05-20-2006, 06:55 PM
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Default RE: a mystery of a ryobi that won's start

You can get engine starting spray at Wallmart cheap. It will start the most sturbborn engines out there. Have some-one help you. Spray in intake while your are turning it over with your starter. Give it a shot about ever 4 seconds or untill it keeps going. Good luck Capt,n
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Old 05-20-2006, 08:05 PM
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Default RE: a mystery of a ryobi that won's start

All great ideas and many things to try.

Can anyone recommend a good thread or website that has illustrations or pictures of walbro or zama carb repair / troubleshooting? This is still all new to me and I find these little carbs somewhat mysterious.

Thanks!
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Old 05-20-2006, 08:33 PM
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Default RE: a mystery of a ryobi that won's start

Just a few other things to check that I can think of .Cylinder to crank case bolts tight &gasket between good? Good gasket between carb& back plate?Good gasket between back plate & crank case? Reed valve loose or damaged?

Good Luck
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Old 05-21-2006, 09:09 AM
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Default RE: a mystery of a ryobi that won's start

Leaks can be found by using air pressure. Use only about 1-2 LBS and block off intake and exhaust. Spray a soapy mix over all joints and seals Leak will show up as bubbles real evident. Capt,n
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Old 05-21-2006, 10:39 AM
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Default RE: a mystery of a ryobi that won's start

Where do you apply the air pressure ? What position is the piston in for this test ?
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Old 05-21-2006, 11:27 AM
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Default RE: a mystery of a ryobi that won's start

You could just use a compression gauge in the spark plug hole, that will tell you if you have a leak somplace. Sounds to me like there is a leak between the carb and the head somplace, if you have already checked the carb out. Course, my advice is worth what you paid for it
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Old 05-21-2006, 02:10 PM
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Default RE: a mystery of a ryobi that won's start

Careful here guys. For one thing, the newer formulation of WD-40 doesn't burn. (It's actually the propellant that burns anyway.) So that can be a false test to try WD-40, as if it's the version that won't burn, it won't run the engine. Another thing is that I really don't recommend using ether (starting fluid) on two stroke engines. Ether is very dry, and the poor engine is running with ZERO lubrication when it's running out an ether injection. Not good! I've seen some badly worn/galled pistons from people using ether in two strokes.

Also be careful with that pressure test. You have to completely seal off the intake, exhaust, and spark plug hole, and inject no more than 3 psi of pressure. Much more than that will blow out gaskets and seals. Then you can use soapy water to test, or hopefully you have a gauge to monitor the pressure and you can see if the pressure holds. It is best to check an engine this way both in pressure and vacuum. It doesn't matter where the piston is for this test, and you can inject the pressure or vacuum anywhere it's convenient.

Anyway, the easiest thing to do here is try another carb since you are not a carb expert and may not know if your carb has a problem or not. Since the engine will try to run, I do not think you have any kind of ignition problem.

Good luck,
AV8TOR
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Old 05-21-2006, 02:54 PM
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Default RE: a mystery of a ryobi that won's start

check the fly wheel key. when it runs does it sound like it has a load on it? the ignition timing sounds way off. good luck
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Old 05-21-2006, 03:55 PM
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Default RE: a mystery of a ryobi that won's start

That was going to be my next idea to try. The spark has to be at the correct time. Hey....that engine has gotta run one of theses days!!!!
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Old 05-21-2006, 04:13 PM
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Default RE: a mystery of a ryobi that won's start

I thought that ryobi's had fixed timing and the only way to change it was to get rid of the flywheel or shear off the key?
If i'm wrong, it sure would explain my problems.
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Old 05-21-2006, 04:56 PM
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Default RE: a mystery of a ryobi that won's start

sboxer
check the woodruf key to be sure , but my money is on the carb, sounds like it sat for a while . pull the covers off top and bottom pull needles out (mark them hi&low )clean with carb cleaner flush out pasages real good then reasemble and try again. set needles two turn's open to start on gasoline (pump variety) .
sboxer why do you run them on white gas ?
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Old 05-21-2006, 05:38 PM
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Default RE: a mystery of a ryobi that won's start

You've already determined that if has good spark. You know it's pulling in air. All you need is properly regulated fuel flow, and it will run. It's the carb. Buy a carb kit for it.

Putting WD-40 or ether inside the engine to start it is going to screw it up for sure. These engines are made to run on gasoline and oil mix--not WATER DISPLACER or ETHER. So, if you DID get it to run on ether--what could you possibly deduce from that? What exactly would it tell you if the engine ran on ether? It would tell you that the spark and air is good--but the FUEL DELIVERY IS SCREWED UP (carb) Don't put WD-40 or ether in it. Thats just dumb.

You got spark. You got air. It's a fuel problem. You don't need to drown it in ether to figure that out. 99% of the time these 2-stroke engines have a problem, it's the damn carb.

You don't know how long it's been since the carb was rebuilt. You don't know if the carb was left wet at the end of the last run, and allowed to dry out. This will cause all kinds of problems if the engine is left in storage for a long period of time with fuel in the carb. The fuel evaporates, and leaves the oil behind. Gums things up. Also, a lot of the gas sold today has ethanol (alcohol) in it. That makes the diaphrams stiff. So, while the carb diaphrams may appear fine--they may actually be too stiff to function properly. I've seen this before.

Carb kits cost about $10. There is a model number stamped on the side of the carb. It's right next to the needles on the carb body. If it's a Walbro carb, then the model number will be 2 letters usually folowed by 3 numbers (WT 348) (WT 435) (WA 127)

Rebuilding a carb is easy:

Pay carefull attention to the gaskets when you take them off. There are 2 gaskets on each side. The side with 4 screws--the thick gasket goes on first and the thin gasket with the metal washer on it, goes on last. The side with only 1 big screw--thin gasket goes on first, followed by the thicker one. Don't over tighten screws. The gaskets are soft, and so is the aluminum. Snug them up--then leave it alone.

Replace the main jet too. It's included in the kit. The jet is under that gasket with the little metal washer on it. There is a little fork-shaped piece of metal that pivots back and forth on a small steel shaft. There is a small phillips screw holding it all together. Be carefull when removing that little phillips screw. There is a tiny spring under there, and it usually ends up flying across the room if your not careful. Good luck finding it, if you drop it. This is best done inside a shoebox or other container, so that if you do loose the spring, it's at least contained inside the box for retrievel. Now pull the jet out and just drop the new one in. Put the spring back and line up the fork. Put the small phillips screw in and tighten just a bit snug. Remember--this is aluminum we're working with. DON'T MONKEY KNUCKLE the screws. [:-]

Pull the welch plugs out. The welch plugs are small round aluminum plugs about the size of a pencil eraser. There are 2 of them on 1 side of the carb. You can remove them by using a sharpened punch (awl) to pop a hole in them and then pry out. Check the screens underneath for gunk and debris. Clean with pressurized carb cleaner from a can. Replace welch plugs with a small hammer and a wooden dowel. Put a tiny dab of clear fingernail polish on them before you pop them back in. This will glue them in and keep them from coming out. Put the wooden dowel on top of the plug. Tap lightly on the dowel with a small hammer. Wipe off excess finger nail polish with a paper towel.


To adjust carb:
Carb will have an L and an H stamped on it. High speed needle and Low speed needle.

Adjust the high speed first:
Run the engine up to full throttle and turn the H screw in (Lean) untill engine reaches max speed and then slows down. Now back the screw out again the other way untill the engine picks up speed again and then slows down. That will be just slightly rich. You want to run it a bit on the rich side.

Adjust the low side next:
Same as high side. Turn the L screw in and listen to the engine pick up speed. Turn it in about 1/4 turn at a time untill you hear engine slow down or maybe even die. Now back the screw out about 1/4--1/2 turn and check throttle response. It should be snappy. Engine should idle well for at least 30--45 seconds and then snap to attention instantly when you give it full throttle. If it stumbles and stutters when you throttle up--it's still a bit rich. You can lean the L needle about 1/8th turn at a time untill it's nice and smooth on transition.

Go back and double check the H needle to make sure it's still a little rich. Adjusting the L needle has an effect on the H needle, so be sure and doublecheck the H needle after you tune the low end.

You may have to adjust the idle screw after tuning the L needle. If the engine was overly rich, and you adjusted the low needle, it will make the idle speed up. Just back that big screw (with the spring on it) out untill it idles at the speed you want.
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Old 05-21-2006, 06:17 PM
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Default RE: a mystery of a ryobi that won's start

Wow! Thanks for all the information. I have more here to work on that I expected or could have hoped for.

A few comments: I use white gas because I hate getting the smell or gas on my hands and clothes. White gas is odorless.

I have always used a quick squirt of ether to "prime" the engine as in the past it has kept me from having to run the engine up with the choke on (now removed). My starting procure was to cover the carb with my finger and turn the prop until I could see gas in the line and get my finger slightly wet, then hit it with a drop of ether and the electric starter. I think the ether helps the engine as the fuel starts to flow and the engine warms up.
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Old 05-21-2006, 07:25 PM
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Default RE: a mystery of a ryobi that won's start

Quote:
Putting WD-40 or ether inside the engine to start it is going to screw it up for sure.
Simply not true.

Bill
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Old 05-21-2006, 07:56 PM
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Default RE: a mystery of a ryobi that won's start

sboxer
how does it run on white gas ,do you get the same performance as gasoline? as I understand white gas has like a
50 octane rating what about timing,spark knock etc.?
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Old 05-21-2006, 09:24 PM
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Default RE: a mystery of a ryobi that won's start

I just started using white gas and as far as I can tell the it makes no difference. I read some threads here before I tried it and the consensus seems to be that it works fine. I costs a $1 more than regular unleaded (on Long Island), but I like the convenience of it.

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Old 05-23-2006, 09:58 AM
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Default RE: a mystery of a ryobi that won's start

Just to update the thread, I am going to pickup a carb rebuild kit and see if that helps. Thanks to all for the input (esp Rcpilet ) for the details on rebuilding carbs.
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