OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Trimmers and Brushcutters Ryobi Trimmers & Brushcutters Ryobi Lawn Hornet 1100 MK III Leaking

Hi All, I was given this Ryobi brush cutter not working and am trying to bring it back to life. I have never had one so all new to me.

When I received it it was all covered in oil. I expected there was a leak so cleaned it whit a degreaser solution. I emptied and washed the fuel tank which had some melted rubber ring inside (maybe from the cap) on very old fuel.

i took the carb out and it seemed clean, so did not want to mess with the gaskets or diaphragm as i saw someone in youtube saying Ryobi doesn't provide kits anymore. The carb is a WT148A I then replaced the air filter (made my own out of foam) as it was almost non existent Checked the spark plug and looks clean and new. I investigated the petrol/oil mix and the recommended seems to be 25:1 so went to bunnings and bought the Ryobi 2 stroke "high quality" oil and prepared a small amount of fuel for the initial test.

After a few tries I managed to get it running but it died out after some 10 seconds or so. I never got to switch the knob to the run position. The problem seems to be a large leak showing at the exhaust. I opened it up, removed the plastic cover at the back (where the air filter is held) gave it a wipe and tried to start it with the cover off. this was not a good idea as it seems to shoot fuel out of the carb (through a hole which would be normally blocked by the choke knob.

When I took the cover off, there was a small amount of fuel around the carb but the exhaust had a lot more. I am not sure whether the leak is in the exhaust or whether it is dripping into it from the carb (which is located right above it) I managed to get the cutter started a second time but again died after a few seconds. Once it dies I had to try hard to get it to start again and the fuel seems to be pouring out of the exhaust.

So, does the fact that the cutter starts mean I don't need to replace the carburator? I realised the WT148A has been discontinued and I would have to get a WT148-1. I suppose it will be similar

this may seem like a silly question but if the leak is in the exhaust, how can all that fuel make its way there without the engine even starting? is the carb doing what it is supposed to be doing? I must clarify there is no priming system on this equipment.

Thanks in advance for your help!

Some photos below

The first thing we need to get straightened out is your starting technique. Brushcutters, chainsaws, and other tiny 2 strokes that use all-position diaphragm carburetors pretty much all start the same way. You turn on the ignition, set the throttle to the start position, apply full choke, use the primer if it has one, then pull the starter several times briskly. If all is well, after about three pulls the engine will start then stall after a very short time - usually less than a second. You then open the choke to the part-choke position if it has one, or if it hasn't, open it to about 3/4 choke. Leave the throttle in the start position of course. Then you pull the starter again. Normally it will start on the first pull this time, since it has a belly full of fuel from the full-choke run it has just done. After somewhere around 15 seconds to 1 minute running that way, you will notice some smoke in the exhaust and it is time to open the choke fully. Then all should be well, though you may have to wait another minute before it will idle (meaning, you wait before you release the throttle from the start position). Don't let it idle for long, even after warm-up, or you'll probably foul the spark plug.

From your description you have been keeping the choke applied. Consequently raw fuel was ejected into the muffler and a few other places.

Please try following the above instructions, and tell us what happens.

Hi Grumpy, thanks for your reply.
I had been following the instructions on the sticker as follows;

-switch on
-choke in full choke position
-pull a few times until the engine sounds like it wants to start
-move knob to partial choke
-a few more pulls (sometimes it started here, but with a quite a bit of effort)
_then I was supposed to let it warm up for about 10 seconds before moving the knob to the run position but did not have the chance as it stalled before that.


There was smoke on start up and came up very noisy. Not sure if stalling was due to me relieving the throttle trigger a bit or to do with the fuel leak issue.
Other thing i noticed is the rope getting too hard to pull sometimes and sometimes it would be too lose as if something came undone inside. After a few pulls it was back to normal.

Most fuel seems to be dripping at or from the exhaust but I guess it could be the carb which sits directly on top. I took the plastic cover off to observe the carb when I pulled the rope, and that is when I saw fuel being ejected. yes the choke was on as recommended in the instructions.

I will follow your advise and give it another go today.

First, you must not "relieve the throttle" until the machine has warmed up - probably for at least a minute on zero choke. Open the choke to the partial position after its initial burp-and-stall. Then start it, and open the choke the rest of the way ASAP. If you do it too soon, it will stop. If you do it too late, it will smoke, spew fuel out the exhaust, stall, and be hard to start again. At this point it is possible that the fuel "leak" you have might be just over-fuelling, resulting in raw fuel coming out of the muffler and the engine rich-loading and stalling.

These things are not easy to use, it takes practice to make them run at all and then they are still pretty ordinary compared with the worst 4 stroke lawnmower you will ever see. There is a reason that so many contractors use the Honda 4 stroke trimmers: they may be heavy, and expensive, but they are very easy to start, and you can let them idle without them fouling the spark plug.

st one more question.

Is fuel meant to enter between the membrane and the metal plate with four screws in the photo below?

I opened the carburator up again today and although I can't remove the membrane and gasket on this side of the carby, I noticed they get moist (some fuel remaining in the carby from yesterday) when I press the membrane. I thought this may be normal (overflow release or something) as there is a little hole on the plate which aligns with where the membrane gets moist. I can't see the perforations in the membrane so they may be very minute.

On the other hand, if this is not normal then I may have found the source of the leak.

You may, Jonez, we need to see some pictures to even guess. There are two diaphragms on the carburetor: one for the fuel pump, and one for metering the fuel. The one with the punched steel cover with the hole in it, that is retained by 4 screws, is the metering diaphragm.

thanks grumpy, yes the meetering diaphragm is the one that permeats fuel. Is this normal?

I just called the Acacia mower Centre in Brisbane to inquire about the kit or even gaskets for this carb and the guy did not want to know anything about Ryobi. Told me it was better to buy a new cutter. Wouldn't even tell me if if had any other carburators that may work.

Sorry, I did not see you reply. we must have been typing at the same time. Taken: what you say makes sense. The engine was rich and hard to start. However the leak starts from the moment i pulled the cord the first time it seems. It seems that was the problem the previous owner had. I got it completed bathed in oil/fuel and had to give it a good clean before I could put my hands on it. I also suspect the two big gaskets in the photo may need replacing.

If the fuel is coming through the metering diaphragm, it needs to be replaced. This is easily done - that is a Walbro WT carburetor, and a standard kit for it looks like this:
http://www.ebay.com.au/itm/Walbro-c...DefaultDomain_15&hash=item19e3ec1005

This fits both WA and WT carburetors (the two most common types), and contains diaphragms and gaskets only. For a higher price you can get replacements for more parts. The bits that don't fit your carburetor will be for a WA. Just put them back in the ziploc bag and forget them.

Note the kit has both conventional and mylar fuel pump diaphragms. The mylar ones are used for American fuel, which commonly contains ether (MTBE, TAME, or whatever). Ether destroys conventional diaphragms.

The kit does not contain a replacement metering needle. Inspect your needle and see if the Viton seating part (black rubbery bit on the pointy end) is worn. If it is, you need a more complete kit.

The two gaskets in your photo are Ryobi parts, not Walbro parts. If they need to be replaced, you may have to get them from a junked whipper snipper.

thanks a lot. I am getting there! So it seems the meetreing diaphragm is perforated. It is hard to see though. It just gets wet when I press it down. It is also stacked to the carb, so I haven't removed it yet. The carburetor is a WT-148A superseeded by WT-148-1 . Apart from ebay is there any other way to get the kits? Are there Walbro distributors around? I was looking at their web site but did not see anything in Australia

You can get Walbro parts through the Outdoorking online store.

Some mower dealers keep the kits and some don't. I don't know of Walbro distributors who will deal with the public. Generally, the online store will be considerably more knowledgeable and more helpful, but there is a minimum mail-out fee of about $20 that hurts unless you buy a fair amount of stuff in a single order. It is great if you want a fairly expensive part, or for the people here who work on lots of engines and have a reasonable throughput of parts. Obviously dealing with a helpful expert is way better than dealing with someone who is neither of those things.

Here is what a WA/WT overhaul kit looks like, rather than just a diaphragm and gasket kit:
HERE

It has a metering needle, metering lever, and some screens and welch plugs.

Thanks very much. I have just ordered the kit in your first link (D10-WAT). only over $7. Checked the needle as you suggested: it was'n black but seemed very good. Checked the ebay store from your the link you posted and realised they also had D10-WTA @ $4.80 which seems to have all i need for now, except that the diaphragm looks made from a different material. For the full kit I see they have the K10-WTA. ($13.50) This would have also been under $20 Thanks again, I will patiently wait for my order to arrive. I will put the cutter together and will update the results then. cheers

The fuel pump diaphragm in that $4.80 kit is mylar - it's intended for use where there is ether and/or ethanol in the fuel, as in the US. I haven't tried using a mylar diaphragm - I've seen scattered reports that it is more troublesome than the conventional one, in that it doesn't always work when installed as casually as a conventional one is installed. Since your metering needle is OK, and you don't have signs of lean mixture, you have a good chance of success just by replacing the metering and fuel pump diaphragms with conventional ones the same as the original ones. There are no indications of any problem with your original fuel pump diaphragm, but since you will have a new one, and they do age, it seems appropriate to fit it in the interests of long term reliability.

Got the kit today and realised it was not the closest to my carby. I know you linked D10-WAT for information only but that is also the kit Walbro recommends for WT-148-1, which is the carburetor that superseded mine (WT 148A).

I had a quick look again and it seems D20-WAT was what I needed. The metering diaphragm is the correct one but the conventional fuel pump diaphragm is not the same. However, the mylar diaphragm suits perfectly. I am now thinking: I could order a new kit, I could leave the old fuel pump diaphragm on or I could use the mylar type.



Looking at the old diaphragm, I see it is not very good flexible so perhaps I will try the mylar type and see what happens.

Sorry Jonez, I had not noticed that the two fuel pump diaphragms for WTs were of different designs. Your old diaphragm has stretched to a saggy/baggy condition and I would not re-use it. In that situation I would certainly use the mylar diaphragm. Just be careful to fit it correctly, it is a lot thinner and more easily wrinkled/folded/ creased than the conventional type. With correct fitting I'll be surprised if it does not work properly. Please let us know how it goes of course - I don't recall a thread featuring a mylar diaphragm, so a lot of people will be interested in your experiences with it.

Hi Grumpy.
Happy to share my experience.


Based on your previous comments I was unsure the mylar diaphragm would work so I decided to put the new conventional diaphragm (top left marked with and x on the picture above) plus the mylar one at the bottom right in the photo. I realised that if I superposed them I would get just the shape I needed. Besides, I wouldn't be adding much to the thickness of the set given the mylar is very thin. I thought if they sealed right there was no reason why this shouldn't work. I used the conventional diapragm first to close the valves on the carburetor and then mylar on top just to close the part marked with the X.


On the weekend I tried starting the cutter a few times but nothing. Good thing is the leak has stopped. This morning I emptied the tank and put the carburetor apart. It did look very dry. Like if no fuel had gone through it at all.


Put the old pump diaphragm and gasket back in it fired up. Used for about 20 minutes in which time I turned it off and on a few times (only gave me troubles once) It was all good until I bumped the head for more string and it stalled. There was still fuel in the tank but could not start it again so left it alone for now.


I still think the mylar diaphragm or the arrangement I had set should work. I noticed I had set the trigger cable a bit too long and perhaps this is the reason why it did not start before.

Next I will use the mylar diaphragm only and see what happens.

There's nothing like applying the scientific method when you need to solve a problem, and that is what you are doing. Personally I would not have expected the double diaphragm setup to work, because the doubled flap valves might be too thick to work, but I haven't tried it, so that is just prejudice, not science. You've found that it didn't work, but not why. If you now try the mylar one alone, and it works, the only possible reason will be something that is different between the double diaphragm and the mylar diaphragm alone.

If the interior of the carburetor was dry, no fuel was being pumped, so the problem was most likely in the fuel pump. You put the old diaphragm back in and it worked for a while, which further supports the idea that some aspect of the double fuel pump diaphragm was the specific cause.

Because the baggy old diaphragm had been working for years, it will quite likely continue to work for a while longer. Hence I do not think it would have been the sole cause of the machine flaming out and not restarting. However if the output from the fuel pump was pretty marginal with the old diaphragm, combining that with low fuel level and a lower starting throttle set-point might just keep the machine from starting. Filling the fuel tank and putting the throttle cable back the way it was originally might get it working again, for a while and in a fashion.

If you continue to go step by step and apply careful reasoning, you should get to the bottom of this. Personally I'd try the mylar pump diaphragm as the next experiment, rather than try to get some action out of the baggy diaphragm. You've said that is what you plan to do, too. I'll look forward to hearing how it goes.

yeah, getting there. Thanks for your help. I will try the mylar alone next. However just to clarify I did not use the the two diaphragms with flaps. Only the conventional has flaps. The mylar part I used is the one at the bottom right in the photo. That one on top of the conventional one gives me the shape of the mylar diaphragm with the tick (which I haven't used yet) in the picture. The problem the cutter must have had to do with the leak, The metering diaphragm was broken and a bit stiff. I replaced it and the leak has gone. I was able to use the cutter for 20 minutes. The pump diaphragm is not broken but is is stiff and not good as you say.

So you used the conventional one second from the top of the center column (with the cross on it) together with the mylar one at the bottom of the right column? Which one was in contact with the carburetor body? Remember that the flap valves can only work if they are right up against the flat metal carburetor body. If you put anything in between, such as the gasket or the mylar diaphragm, the flap valves can't work. So, the conventional item second from the top of the middle column needed to be directly in contact with the carburetor body, and the mylar diaphragm needed to be in between that item and the gasket, which would have been against the pumping chamber cover.

Have you replaced the fuel filter on the end of the pickup hose, inside the tank? If it is restricted by dirt it will reduce fuel pump performance.

Yes, I had used those two in the correct order: the conventional first(in contact with the carburetor body, then the mylar then gasket and then cover lid but it wasn't working.


When I put the old ones back, there were a couple of things I also did. Adjusted the trigger wire to make it tenser and also took the clip that holds the needle and bent the end upwards a tiny bit as it did not seem to be lifting the needle before. So perhaps this helped fix the problem.


I now tested both: the mylar type diaphragm and the conv+mylar set up and both worked. I did not notice any difference between the two. However it seems to me they both are smoking a little bit more and running slower than when I used the old diaphragm. This may just be my wrong perception but it also feels they have a smoother idle run, which is nice.





Again, I may just be wrong or perhaps that is how it is. The old set up is not good anyway, so I don't have a good point of comparison. It may have to do with the trigger wire adjustment (although I thought I kept it within range of where it was )

In short, the mylar type pump diaphragm runs ok at least for now. There is no much to do in my yard at the moment so didn't do much testing. I'll give it some more use next time I mow my lawn to see how it behaves in the long term.

My take on that report is that the mylar diaphragm alone works correctly, but you have now adjusted the metering lever height, in the metering chamber where you had already replaced the diaphragm. If you have done that, it changes the air/fuel ratio of the carburetor. However, you report that it now runs fairly well, so you may have only made a small adjustment (the metering lever height is a rather sensitive adjustment).

Here is the Walbro service manual for your carburetor:
http://wem.walbro.com/distributors/servicemanuals/WTseries.pdf

Please read the manual, paying particular attention to the metering chamber and the metering lever, then clear up a couple of points for me:
1. Did you change the metering lever height?
2. Does your carburetor have externally accessible H and L mixture screws?

If you post a picture or two showing the H and L screws, that will help also. Please do not make further adjustments to the metering lever or the H and L screws until we have these points clarified.

Thanks for the file. 1. Yes I changed the height of the lever by bending a bit the tip that lifts the neddle. But as I said before, this is what I did just before putting the old set back. I did not make any changes now when I tested the mylar diaphragms. The reason I did this is because adjusting the lever screw did not make any difference. When I pressed the spring down, the needle wasn't getting lifted. Probably the previous owner had been playing with it because it looked like the clip of the lever had been bent down. So I brought it up a bit. That is when I got the cutter working continuously for first time. It just happens that I had also put back the old pump diaphragm then. Next I just replaced the diaphragm with the mylar types and confirmed they worked too. 2. yes my carburetor has two mixture screws but i didn't touch them at all.

We are getting there, we just have a bit further to go.

I am not sure what you mean by adjusting the lever screw. I think you mean you were loosening the retaining screw that holds down the metering lever pivot, circled in red in this picture:



That screw should be tightened firmly to hold the pivot in place - it is not an adjustment. The metering lever is adjusted ideally by using a plastic tool, like this:



You can easily make your own gauge out of sheet metal. For WT and WA models, the center bar, which touches the top of the metering needle, should project 0.065" (1.65 mm) below the other two bars, which rest on the flat body of the carburetor at the sides.

It seems from what you have said that you have the metering lever height close to correct, but it worries me that you may not have had the pivot retaining screw tight when you measured it. Because the metering lever is spring-loaded, it rises up when the screw is loose. Unless the screw was tight when you finished your adjustment, it looks as if you need to go through the process with a home-made gauge.

Once you have the metering lever height adjusted, we can talk about making any necessary fine adjustment of mixture by using the H and L screws. If you had the pivot retaining screw tight when you did your test, it sounds as if all that will be needed is some fine-tuning of the high speed mixture screw, but please do not touch that until we have finalised the metering lever discussion.

yeah, I realise I had the wrong idea. However I was pretty sure I tightened the screw firmly. I checked this again and I had done so. All i did was "correct" a bit the clip that lifts the needle as it seemed twisted/stretched.

I made (sort of) the gauge and measured as in the photo ( middle bar resting on the lever) It is quite close. Close enough I would think.

On a side note, I can't help but think this tool would only be useful if I knew my lever had got the right shape. As I said, mine did not look so. Also if you saw the lever was too high, how would you adjust it. would you use a screw driver or something to bend the lever?

At this point, to be honest I am not sure what I should be looking for. It is true I have the feeling the mylar diaphragms made the cutter run slower but I could be wrong, and if not maybe that how it is supossed to run. I don't have much experience with one of this.

I will be interested in learning about the fine tuning even though I may not need to apply at this stage.



Thanks again for all your help, I had fun bringing the cutter back to life and more importantly avoiding it to go to landfill.

Remember you are applying the special gauge to the rounded top of the fuel needle, not the lever itself, so the shape of the fork on the lever is not critical, except that the needle should be supported by both sides of the fork.

Post-edit: The above instruction is wrong, the gauge is applied to the opposite end of the metering lever, directly above the spring. My error. I must be getting too old for this stuff, it isn't long since I last adjusted one of these.

In principle you can adjust the fork either by holding it and bending it in place, or by taking it out. I prefer to take it out, because it is rather springy (it is not dead soft steel) and I do not like to risk having the tip of the needle pushed hard against its seat. If you take the lever out to adjust it, you can be quite careful to bend both sides of the fork evenly. On the downside, putting the lever back in without the spring going ping and disappearing, requires care.

Once the metering lever height is set, adjusting the mixture is theoretically easy but can be rather frustrating in practice. You do it like this. If the carburetor has been stripped completely, you simply reinstall the H and L needles by screwing them all the way in until they very lightly bottom. Then you turn them both anti-clockwise one and a quarter turns. That gives you fuel settings that will allow the engine to start and run, though probably not especially well. Then you set the idle speed screw fairly high, start the engine using the standard procedure, and let it warm up. Once it is warm you reduce the idle speed as low as you dare, or ideally, until the clutch disengages and the cutting head stops rotating. Then turn the L screw (idle mixture) slightly clockwise a bit at a time until the engine suddenly runs smoothly (that is, 2 stroking - it will have been 4 stroking initially). Move the needle clockwise and anticlockwise until you find the most anticlockwise position that allows it to 2 stroke, or just a bit richer (more anticlockwise) than that.

Next step is the H screw (high speed mixture). Open the throttle wide and turn the H screw clockwise until it suddenly smooths out and 2 strokes. Feel around to find the most anticlockwise position (that is, richest mixture) that allows it to two stroke fairly steadily. However do not dally on the clockwise (lean) side of the best position, where it stops 2 stroking and starts 4 stroking. Lean mixture at full throttle can damage the engine. (This is especially true of high performance chainsaw engines, but you should always avoid running on the lean side at high speed/heavy throttle, for any engine, 2 stroke or 4 stroke.)

That is the official tuning procedure. In practice, you may find that when you have done that, there is a lean zone somewhere between idle and the "starting" throttle position. Consequently if you open the throttle suddenly from idle, or if you linger for a while anywhere below the starting throttle position, the engine may hesitate or stall. If that happens it is best to make the L screw just slightly richer than the 2 stroking position, to overcome the problem.

wow, I am glad I did not touch the L and H screws. Great info but I will have to read it a few times before I try that. thanks again!