OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Trimmers and Brushcutters Two Stroke Trimmers & Brushcutters Ryobi trimmer stalls when taken off choke

Hi all, i got myself a near new Ryobi whipper snipper which has not seen much use at all.. It starts fine with choke on, but as soon as i slide the choke off it stalls.. It will not idle unless throttle is applied. As soon as the thotle is off it stalls.

what could be the possible causes given how new the machine is?

any help would be great!

Hi luvpsi. Will it keep running without choke after you warm it up under load for 10-15 minutes? If it will, it's just the same as my Craftsman. You may be able to make it less-bad by richening the mixture, if the screws are not sealed. If they are sealed, you might improve things by cleaning the carburetor, especially the jets, which probably have some gum in them.

thanks grumpy! I have not run it for longer than few minutes so I am unsure if it will work after running for 10-15. Ideally i would like it to idle even when cold I cannot see any idle mixture screws so they must be sealed.. as for cleaning the carby, can i do this with carby cleaner or is carby removal in order?

Post edit: The first point to check, especially when you have just acquired the machine, is the spark plug. Two stroke spark plugs do not last very long anyway, but if the previous owner let it idle for substantial periods, the plug life might be very, very short. Try a new plug of the correct type. Don't throw the old one away: if the new one makes no difference, put the original one back in and keep the new one for next time.

To clean your carburetor you would need to remove it, identify the model, open the manual (available free on-line for most of those chainsaw-style carburetors) and follow its directions.

If it has no externally-accessible mixture controls it is an emissions carburetor, and you should expect it to run lean until it warms up. My system is to leave the choke partly on, and gradually open it as warm-up progresses.

thanks again Grumpy. I fitted a new spark plug and same thing..

I then removed the carb, cleaned all the nozzles, diagphragm etc then refitted and still no good.. it just does not want to run without throttle applied

as soon as i lift the hand off the throttle it dies instantly.

what i know is that it is ryobi rbcgm25ss machine 25.4 cc with Ruixing carb and it is the latest model.

I am really puzzled to what it can be ..

Have you tried screwing the idle speed adjustment all the way in? This should raise the idle speed to at least 5,000 rpm so it would be running on the main jet, not the idle jet. Note I'm talking about the idle speed adjustment, which holds the throttle butterfly slightly open - I'm not talking about the low speed mixture screw.

If it will not run without even more throttle when the idle speed is set impossibly high in that way, please tell us that and we can think further. If it will run in that test (without major throttle but only at high speed) the problem is in the idle system of the carburetor. Unfortunately because Ruixing does not provide any manuals as far as I know, it is difficult to move on from there in any orderly way. Ruixing carburetors are normally fairly exact copies of brand-name carburetors, and I have seen a hint on the internet that yours may be a copy of a Zama. I suggest you try to find your Ruixing in the Zama Tech Guide, which you can download here:

http://www.zamacarb.com/pdfs/TechGuide_2007.pdf

Please let us know whether you can get it to run with the idle speed set ultra-high, and what kind of carburetor your Ruixing is cloned from - then we can work on it from there.

Hi Grumpy, thanks again. With the idle speed adjustment all the way in, it revs higher and does not stall, so it does seem like the idle system is not functioning.

By chance i took a look at my Hitachi blower and the carby on that (Walbro WYC-27) seem near idential to the Ruixing one on the Ryobi..

Will changing the diaphragm and gaskets perhaps solve the problem?

It sounds as if you need to go through the overhaul procedure for the idle system. Start by checking whether it is the same as the WYA covered by this Walbro overhaul manual:
http://wem.walbro.com/distributors/servicemanuals/WYAseries.pdf

Look at Page 5, which tells you how to unseal and adjust the coarse idle mixture adjustment. Then clean out the idle system, and follow that adjustment procedure.

I think it is different. These are the photos of the carby.. At the moment i am happy just to find out exactly what model it is and get a new one if necessary so I can use my machine

Since the Ruixing is not documented AFAIK, and we have found no similar carburetor that is documented, I can't offer any suggestion other than the following:
- check for an air leak between carburetor and intake port: loose mounting, split rubber hose, etc;
- check for a crankcase air leak;
- check for other faults in the way it runs - or is it faultless except it won't idle?
- check that the fuel tank air vent is not stuck (loosen the tank cap and see if that makes a difference).

If it does everything properly except idle, and the above tests do not help, cleaning out the idle system with carburetor cleaner seems the only remaining step. I see no point in dismantling the diaphragms (metering or fuel pump) except as a way to access passages to blow out.

thanks again! and where is the idle system situated? is on the top of the carb (underneath the butterfly)?

If you look at the throttle butterfly, you will see two or three idle discharge holes just in front of the throttle-closed position. Nearby you can hopefully find the idle mixture screw. The bits most likely to need cleaning are from the discharge holes to the idle mixture screw. By removing the mixture screw and squirting carb cleaner into the threaded hole, hopefully it will squirt out of all of the discharge holes. If it doesn't, you may have put the carb cleaner into the main mixture screw hole.

Hi Grumpy,

sorry to be a pain but are you able to draw a pointer to that position on any of the above attached photos?

Also i have been able to locate a fully compatable Walbro carb (WYC-27-1)from USA which will fit the same way as mine.. Question is will the motor work the same as with the Ruixing carb? Are the mixtures specifically adjusted on each carb according to the machine they operate on?

Thanks

luvpsi, none of your pictures shows the area around the idle discharge holes in the carburetor bore near the throttle plate. Here is the idle system explanation from the Walbro Service Manual, Page 7. I have circled the bits you are interested in, in yellow:



If you can remove the adjustable idle screw and squirt carb cleaner into the hole it comes from, you should find the cleaner blasts out through the three holes just before and after the throttle butterfly plate. Hopefully it is not necessary to interfere with the adjacent metering chamber, because the engine runs properly off-idle and at higher speeds and loads: the problem is likely to be in the idle pocket and the area immediately around it.

Carburetors are "flowed" at the factory to match a standard air fuel ratio profile across the operating range. Mixture controls are adjusted to align closely with the profile, then sealed. There is no attempt to adjust mixture after attaching the carburetor to the engine. Hence if you fit a carburetor intended for the same engine size and type, it should be fine. Subject to emissions control regulations, later service adjustments may be either easy or difficult.

In case it makes useful light reading, here is the full Walbro Service Manual:
http://wem.walbro.com/distributors/servicemanuals/ServiceManual.pdf

Brilliant! That helps a lot. I will try and clean those chambers and then see if it makes any difference!

Hi Grumpy one final question i promise

in the attached diagram can you please point to where the idle adjust screw would be just so that i am 100% where to dismantle:

Here is the plug covering the idle mixture adjustment on your carburetor, circled in red:


Here is approximately what you will find under that plug (this is from the Walbro WY manual) circled in yellow, with some adjustment information for when you put it back in:


It would be a good idea to record where the adjustment is currently set, before you unscrew the needle. And be gentle with that needle.

Thanks Grumpy. Unfortunately the Idle screw setup looks a bit different on this carb as this is a 'Rotary Valve' carb and does not have the usual butterfly setup.

I took the screw off anyway but there are no passages to clean as the needle goes directly into the main jet below

As a side task, I took the Walbro WYC-27 off my blower and fitted it to the trimmer. The results were impressive. The trimmer starts first go (even when it was new this machine did not start first go with Ruixing carb) and runs like a dream.

So after not being able to do achieve any kind of improvement I have ordered a genuine Walbro Carby from USA for around $45 which I think is better then stuffing around with rebuild kits that will not guarantee a good result.

Many thanks for all the help!

I agree that a rebuild kit probably wasn't any part of the solution, luvpsi. I suspect, though, that the fixed jet you found underneath that blanking off screw on the Ruixing is actually the idle jet, not the main jet. You might try removing it, inspecting whether it is blocked, cleaning it, and blowing carb cleaner through the passageway containing it. In other words, it may be just like the one I posted except for having a rotary valve instead of a throttle butterfly, but it probably has idle ports anyway, so the carb cleaner will gush out from near the edge of the rotary valve.

If you carry out this check, please post the outcome here. I'll leave the thread open.

Incidentally I am not questioning your decision to put a Walbro on your trimmer instead of the Ruixing, because you know that will work well, but it will be useful information for our other members, and our archives, if you post an outcome. If cleaning the idle system makes the Ruixing burst into song, other members will be able to save their money on buying a new carburetor.