Ryobi Gas String Trimmer

I have a Ryobi 15 inch, two cycle, gas powered string trimmer. I have having trouble keeping it running after start up.

The starting procedure from Ryobi is as follow:
1) Turn switch to "on" position, close choke, depress trigger and pull cord 2-3 times until engine tries to start
2) Move choke to halfway position, depress trigger and pull cord to start
3) Allow engine to run for approximately 10 seconds, move choke to full open and proceed

I follow these instruction and the engine starts without any problem. However, after the engine runs for a few seconds during step 2, the engine cuts out. If I can keep the engine running long enough and move the choke to the full open position, it immediately cuts out.

This problem has progressively worsened. I have checked and cleaned the air filter, fuel mix ratio is precise, the fuel lines and inlet appear to be okay and free from debris.

What can I check or adjust to keep the trimmer running? I hesitate to adust anything, because it starts without a problem, and when it is running, it works great.

I appreciate the feedback.

Thank you--

MGM

 

Hello MGM and Welcome to the Do-It-Yourself Web Site and my Small Engine forum.

Based on your Excellent problem description, sounds like the fuel ports {Fuel Holes} within the carb are restricted.

The fact that the engine starts with the choke closed but dies when it is opened, is do to the fact that when the extra air rushes in, it dilutes the fuel volumn so much the engine dies.

There may be a fuel entry restriction into the carb or some restriction within the carb. Best bet at first is to try to clean/clear the restriction by using canned carb cleaner.

Carefully insert the plastic entension tube, that comes with the can of cleaner, into the fuel inlet of the carb. Allow a burst of cleaner to enter the carb. Also do the same into any Low {L} and High {H} speed fuel air adjustment screw holes.

TIPS:
Turn the screw INWARDS first, noting how many turns it takes to lightly seat the screw. Make a written note of it. Then remove the screw.

DO NOT interchange the screws. Note which screw goes into which hole.

When re-installing the screws, turn it in fully and back it out the amount is was set at prior.

If your successful, this method may resolve the problem without having to remove the entire carb from the engine and rebuilding it.

Regards and Good Luck,
Forum Moderator
Accurate Power Equipment
Small Engine Service and Repair Technician.
Personal Quote:
"If it ain't broke, don't fix it until it is broken!"
Bare in mind my company no longer services nor repairs lawn and garden powered equipment. The information provided is specific and accurate to the best of my knowledge.

 

Tom--

Thanks for the advice. I tried to do what I could.

The fuel line leading to the top of the carburetor is tightly fitted to a barbed connection. I'm afraid that if I pull with enough force to remove the line, I may not be able to reattach. The fuel line at the base of the carburetor is attached via an elbow-like fitting. Again, the same concern arises.

As for the adjustment screws, this too is a challenge. There are two screws with plastic tops-- one white and one black. The plastic tops are shaped in such a way that the two screws interlock and I cannot turn either one any more that one-half to three-quarters of a turn. I cannot lightly seat or remove either screw because of the interlock.

I tried to spray the carb cleaner inside the port at the air/fuel mix chamber entry, but I don't think that was successful. I also removed the side plate with four screws that covered the diaphragm, pulled back the diaphragm and sprayed the carb cleaner. Again, this wasn't that effective.

I attempted starting the trimmer. As usual, it started as would be expected when the choke was halfway open. However, after moving and turning the trimmer, the engine cut out. I restarted the engine, let it run for a few seconds, moved the choke to full open, then the engine cut out.

Do you have any suggestions as to how I can gain better access to the fuel lines and adjusting screws without causing any damage?

I would appreciate your thoughts on this and anything else I should check.

Thanks--

MGM

 

Most of the limiters are just platic caps that can
be pulled off to reveal the metal screw underneath.
The fuel filter and line are pressed into the
hole in the tank, but if you see no sign of leakage,
I would leave them alone. The line at the elbow
going into the carb can be worked off carefully with
a small screwdriver. But you need to remove the carb
and take it apart and clean it. If you are careful
you should be able to reuse all the old diaphragms.
Fish

 

Hello MGM

Fuel hoses can be removed from the barbed fittings by twisting and turning the fuel line that is ON the barbed fitting. A needle nose pliers works.

Use only enough plier gripping pressure to hold the hose, not damage it, yet enough squeezing force to hold the hose yet NOT grip the barbed fitting.

Follow the advice of Fisher also regarding the hose attached to the fuel tank. You'll be glad you avoided it.

When you remove the fuel inlet hose from the carb, notice how musch fuel flows out. Should be a full steady stream that continues until the tank fully empties.

The filter inside the tank may be restricted, the vent cap may be restricted or the filter may be attached to a hose inside the tank. If the filters is attached to a hose, it must be free to move around within the tank.

 

Tom--

I would like to thank Fisher and you for your advice. You were right on the money!

I disassembled the carburetor, removed the fuel lines and hit all the connections with carb cleaner. I am happy to report that I used the trimmer last evening. It started -- and remained running -- until I was finished. No problems.

Thanks again for all of your helpful advice.

MGM

 

Hello MGM

On behalf of myself and everyone else who contributes helpful advice to the "Small Engine" forum, I'd like to say it's nice to get replies with successful results back.

And "Atta Boys" too!....

Regards,
The Forum &
Moderator

 

Hi there I have a 2 stroke Ryobi grass scorpion . I to have a problem with the fuel hoses. There is a filter in the tank which has a hose attached . there is a primer button 2 hoses. and the carb has 2 connections . one connection to the top of the carb and one to the bottom. Can any one tell me which hose goes where please. which way does the fuel run ? how do i connect the hoses ? thanks Bernie

 

With the engine in the operating orientation, the line off the top of the primer bulb goes to the top of the carb.
The line on the bottom of the primer bulb goes to the fitting on the center of the fuel tank and the line off the side of the fuel tank goes to the bottom of the carb.

My question is what size are these fuel lines?
I bought some hose from a mower shop today that looked like the right size but it isn't. It fits too loosely on the barbs.

 

Thanks for the great advise on the fuel hoses it worked a treat . The fuel hoses I purchased ...I took a sample of my old ones and showed it to him . and he gave me the hose that matched. so sorry I dont know the actual size . Cheers Bernie

 

I ended up going back to the mower place and the nice lady there gave me the next size smaller. Worked great. Glad I could be of assistance.

 

My 2 cycle gas trimmer will not stay started. I just pulled it out after the winter and have a huge problem. Will start on full choke and after a bit on half choke. When I go to switch it to run, or press the trigger to run it, it dies. .. At the end of last year it ran perfect and is only a year old... any suggestions???

The carb that I have is a Zama and the adjustment screws have plastic over the adjustment screws...do you remove the plastic or is the special tool to get the cover off? also which screw is low speed and which is highspeed?

 

I had the same problem as others: Trimmer only runs on 1/2 choke, but fails when switched to 'run' position. So, I followed all the cleaning advice listed ... did not rebuild carburetor.
Now it doesn't start at all. With rare exceptions, these and other similar 2-stroke machines cannot be serviced by ordinary folks who can do plumbing, carpentry, masonry, musical instrument repair, etc. By the time you trace down parts for discontinued models or send them in to a repair service, you're better off kicking the g-d thing to curb and buying a new one ... just expect it to become unusable in 5-6 years and you'll retain your sanity. That's my opinion and you're all welcome to it.

gone shoppin'
Curt

 

I had an echo trimmer that would start and run for about 5 seconds before stalling. I found that the spark arrestor was completely clogged. Take off the muffler and see if there is a screen behind it. If so make sure it is clean so that it does not build up back exhaust pressure. Worth a look.
Best wishes. Robert

 

I bough a Ryobi 725R from a friend who could not get to run after several months dry, in storage.
It had spark and it would run for several seconds after starter fluid was applied to the carburator venturi so I figured
it to be a fuel problem or a carburator problem.
Took carb. apart, blew out pasages after cleaning and installed new pump diaphram and gaskets that came with the over priced rebuild set.
It now would run but not well enough to be utilized.
At least it had idle and high speed adjustable jets to mess with.
I finally bough a new carburator, Walbro W1-539-1.
It was wourth the $38 I spent.
The trimmer runs now like it was new.
I am finding that most of my 2Cyl. engines on my power equipment fail allot more often than they used to when they had carburators with floats and the fuel was gravity feed.
Now days the fuel is pumped by a diaphram in the carb. up to the carb. and the fuel seemes more hostel to filters and carbs. than it use to be.
Walt

 

Hi All...

Came across this forum with a google search on "ryobi trimmer carburetor adjustment."
My Ryobi is only four years old, and I love it...or did, until last year...had all kinds of problems getting/keeping it running. My fuel line was cracked and I assumed it was sucking air and losing prime. I replaced the fuel lines and then had a slight leak at the tank where the line entered. I epoxied the line and solved the leak, but the trimmer wouldn't run right. I could only get it to run in the choked ("A") position, as soon as I moved the choke lever to B or C (partially/fully open) positions, it would die out...I could only keep it running somewhere between A and B.

After reading this thread, I realized the jets must be clogged and the extra air was diluting the small amount of fuel getting in. I had already removed the colored plastic tabs from the tops of the adjustment screws last year hoping to adjust the low and high idle. I removed both screws today and the white plastic spacer they run through before entering the carb. I then took carb cleaner and sprayed liberally into the openings, allowing the cleaner to drain out the carb throat (I took off the air cleaner cover and filter.) I then sprayed compressed air through both holes.

I re-inserted the adjustment screws (I put each fully in and then backed out one-and-a-half turns each) and my trimmer runs like it did when it was new!

Thanks for a great site and a great bit of advice....

Pete

 

This thread has been a big help to me, too. I replaced my gas lines (which were totally rotten) and cleaned my carb (thanks to a doc I found elsewhere that gives a step by step for Walbro carbs).

But, I have one more problem. The line from the top of the carb to the primer assembly leaks a bit of air at the carb. I believe that what this does is causes a loss of prime... all the fuel in the carb leaks into the cylinder, causing my next pull on the starter to be very hard, and all the unburned fuel is pumped out the exhaust.

I replaced all the fuel lines with 3/32 line from Home Depot, and had some leaks to start until I figured out how to pull the connectors out of the gas tank and put the hoses on them rather than just shoving the hose on from below.

Now I'm thinking that one section of tubing is a different size... if it would just seal tighter I think the vacuum would hold the carb full of gas.

Any thoughts? Right now the thing starts and runs until the gas from priming it (that hasn't run out the exhaust) is gone, and obviously trying to start it is a heck of a fire hazard...

Erik

 

Gas should not be getting into the cylinder like that. The primer shouldn't even be squirting gas at all. I'd say either the fuel lines on the carb are backwards, or you have other problems in the carb. The primer should pump gas into the tank, and pull it from the carb.

 

I think I'll start another topic for this, with a description of what I've done to date. It's frustrating me so far.

Erik

 

The pull rope on my Ryobi SS30 string trimmer has become hard to pull and won't start. Last time I used it there was a sound like something coming loose inside and it stopped running. Is there any good disassembly instructions available so I can get in and take a look at what's going on? The user's manual doesn't go into this depth.

 

Take the muffler off and look into the cylinder. I'm betting the cylinder and piston are scored. If so, it's not worth repairing. If you need further assistance, I suggest starting a new thread rather than tagging onto this one that is ~8 years old to avoid confusion.

 

I agree with Cheese's post. Likely the piston and cylinder is scored. I had the same thing happen to me. Being the DIY guy that I am, I took it all apart. Sanded all the parts to remove the scoring and put it back together. It is running fine ever since. I still to this day have not idea what caused it. You you have more time than money you can do the same as I did.

 

You know, I was going through the same thing with my trimmer. The trimmer head would barely spin with the throttle wide open. I replaced the gas lines and filter. Removed the plastic anti-adjustment caps on the mixture needles. Disassembled the carb and cleaned it, all to the same effect.

What got it running propperly was tinkering with the exhaust. If you take off the back side of your motor housing, (2 screws on the upper part of the motor shroud and 4 on crankcase) it will allow access to the muffler. There is a restrictor in the muffler. It reduces the exhaust port from about 1cm X 1.5 cm to 1 cm X 3 mm. This narrow opening gets choked up with carbon and does not allow the engine to breath. There are a couple screws holding on a small deflector that directs the exhaust to the back, remove that and underneath is the restrictor. Take it out and re-installed the deflector, then put the shroud back on.

After doing this, it was like running a new machine. It sounds like a chainsaw now. Plenty of power. The blower attachment and trimmer have more power than I ever imagined the piece of junk to ever put out.

 

Exhaust blockage is a big problem in 2 stroke engines. Cleaning as you have done is suggested each year...No matter if you run additives or not the corbin will buildup and cause back pressure which is like a diesel brake on a Mack Truck.

Have A Great Day!!

 

I'm probably just one of many people who've been helped by this thread. I just wanted to say thank you on behalf of all of us - to everyone who participated - thank you very much!!

 

Im new to this forum but wanted to thank "fireman pete" for his post. My Ryobi line trimmer hadn't worked for a few years and I was just about to buy a new one. I'm no mechanic by any means but decided to pull it apart and spray it full of carburetor cleaner I got for $10 from my local car parts store. Taking it apart was easy as these things have hardly anything to them. Cleaned the ports, cleaned the fuel tank and put together. Kind of started then would cut out, and when did run it would have to have a bit of throttle and had fair bit of smoke. I knew it would have to be the fuel line screws but didn't know how to adjust them. As per his post, I screwed them in fully then counter clockwise 1 1/2 turns.
Runs like a dream now. Very happy...