OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines Briggs & Stratton 500 158cc starting problems

Hi everyone,

I was having some issues with my mower revving up and down, received wisdom would indicate possibly dirty carby so I took it upon myself to remove it and give it a clean out. After doing so and putting everything back I've now got two new problems:

1) When I was removing the carby assembly, this part fell out... I think it might be from the carby assembly, but I'm not sure! If I knew what it was called I could have tried an online search but am at a complete loss.

2) I foolishly didn't pay attention to how the governor/throttle assembly was before I started disassembling. After reassembling the carby this is my arrangement with the throttle cable (at the handle up on the handlebar) @ off:


and @ on:


For you who are much more knowledgeable than me you will notice that the white triangular part controlling fuel flow into the engine (choke?) is in the same position in both pics, indicating a problem (and it is in the open position?).

So as it is the mower won't start and I'm wondering if it has something to do with the tiny part in my first question, and/or how the governor is sitting in the last pics.

Sorry for the longish post, any suggestions appreciated.

Need to post your engine's numbers. I am not familiar with Victa setup.

On the triangle piece that is the carburetor's throttle control plate assembly and it position is normal as the governor will close it as needed upon engine start. This setup does not have a choke; just a primer.

That small piece is either a check valve or a metering jet. I haven't seen one on a pulse prime carburetor but that we need to look the engine's ipl. We can't do that without the engine's numbers.

Hi Funzo and welcome to the forum.
The governor setup is correct. so even with the jet out of position it should still start(even momentarily) once you've primed it 3 times.
The jet has fallen out of the bottom of the spray tube. It's something that has happened a bit on the newer pulsa prime carby's. It lives under the mesh filter at the bottom of the carb and should snap back in but may fall out again depending on how poor a fit it is.
Hunting is caused by several factors and usually starts with air leaking in the fuel delivery system somewhere or an over revving engine also has a tendency to hunt. Replace the jet, use a new diaphraghm if you haven't already done so and report back to see if the problem has been rectified.
I've also deleted your other thread on the same issue and will get one of the other moderators to move this topic to the right place.

bigted. Could you possible shoot me picture of this new design? I know I probably encounter this in the near future just would to what things look like for reference.

I am still learning this forum so I don't if there a way send me PM about it or not.

I also got to use to the language terms differences too. I thinking that what your calling a spray tube we call a nozzle here in the US.


AVB

Funzo, I agree with AVB that we need the engine's Model, Type and Code, so we can link it to the Illustrated Parts List and make this thread coherent and useful to other members. They will be stamped on the top cowl of the engine, or on a sticker that is fairly easily visible.

Thanks for handling this bigted, I could not identify the loose part. I have not seen a Pulsa-Prime main jet detached from the carburetor before, and thought they were not detachable.

Shouldn't the speed control cable have a cable tie around the top of the carburetor, to keep the cable inner from buckling where it projects from the end of the outer? We had a case involving a buckled one last week:

https://www.outdoorking-forum.com.au/forum/ubbthreads.php?ubb=showflat&Number=61198#Post61198

Thank you for your responses!

So the jet sits inside the mesh filter? With the narrower end pointing down?

I had another thought: does the position of the 'hinge' that connects to the engine block from this linkage (circled in yellow below) matter, or is this just where it is? (sorry bit hard for me to picture this with the cowl on)



Here are the engine details. I will try to have another crack at the mower today and will report back.

That "hinge" is the connection between the governor arm and the wire link to the throttle on the engine. Hence it moves when the engine is running, to keep the engine speed steady at whatever you set it to with the control lever, regardless of the load on the engine. Make sure there is nothing obstructing that linkage.

Some details on your engine. First, it was made on 27 September 2011, in the Briggs plant at Chongqing, China. All Briggs side-valve engines are now made in China: the small ones like yours have been for about ten years.

Here is the Illustrated Parts List for your engine:
http://bsintek.basco.com/BriggsDocumentDisplay/18ktxIXUnfBhU7y.pdf

You can use that to see what parts there are, what they look like, how they connect to each other, and what their Briggs part numbers are.

Here is the Operator's Manual for your engine:
http://bsintek.basco.com/BriggsDocumentDisplay/iorpzNJU0HCjhJvcv4.pdf

You can use that to see how to operate and maintain your engine correctly.

Thanks Grumpy. I have the manual but the parts list link is very handy, thanks.

I've disassembled, cleaned the carby, diaphragm and gasket with carby cleaner, emptied fuel tank and cleaned out, replaced with fresh fuel, replaced the jet, reassembled and still no dice.

When I pull the cord the engine must be igniting momentarily? because I can smell exhaust but there's no further cranking, after repeated attempts there's no further ignition at all.

So best bet would be to replace the diaphragm, or entire carby assembly to be sure?

Which way around did you put the main jet back in, and is the hole in the center of it clear?

Did you separate the gasket from the diaphragm, and if you did, did you put it back together the right way - diaphragm against the fuel tank, then gasket on top, then carburetor on top of that?

Did you pump the primer three times, and was petrol squirting out into the throat of the carburetor?

I put the jet back with the narrow end pointing down (ie. wide end into the carb body), it was clear. Yep the diaphragm and the gasket were separated; I put diaphragm against fuel tank, then gasket on top. Both seem to be okay as far as I can tell, there were no obvious buildups or rips. Though I guess it is quite a delicate thing, everything has to be just right on it in order for it to do its job. The primer was working, petrol was squirting out. Just in case I checked the spark plug, which did have a bit of black deposit on it, I cleaned that too but no cigar.

(Happy Australia Day btw, really appreciate you spending time with this today!)

I think you need to test the spark. To do that, remove the spark plug, reattach the plug lead to it, and ground its metal base (the part with the thread) against a metal part of the engine. Hold it in that position and pull the starter cord. Watch the gap between the electrodes for a steady series of blue sparks while the engine is spinning.

Ok just gave that a go, there were sparks.

Good so far. Now, when the speed control is in the starting position, the throttle should be wide open - turned all the way to the stop clockwise, due to the governor spring being stretched.

AVB, Grumpy, Funzo and ODK members,
Here are a few pics of the difference between the earlier and the late model jet setups on the pulsa prime carby's.
The first pic shows the later model one with the jet removed on the left, notice how the hole is much larger.

And here's the jet.

Last pic with the jet fitted.


Funzo, the jet goes in with the tapered side going into the tube.
I'm still not convinced the carby is not the reason it's not starting although it doesn't eliminate the fact there may be a problem with it.
If you prime the carb, and you have spark, the motor should run for a second or so at the very least. I think a new plug would also be a good starting point. Just because it generates spark at atmospheric pressure, i.e. outside of the engine, doesn't necessarily mean it generates a spark under compression.

Thanks bigted, that has improved the clarity of this thread, and given it a better chance of being a useful archive. I agree with you the problem is probably the carburetor, but have been aiming to go through the standard process (check spark, compression, fuel) to give Funzo the best opportunity not to get into this situation again. The remaining steps, once he verifies that the throttle is open when the speed control is in the start position, are to check compression, then try putting a spoonful of fuel directly into the cylinder. If it doesn't start at least briefly when he does that, it will be time for a new spark plug. On the other hand if it starts then stops, it will be time to begin again at the beginning on the carburetor process, this time step by step. This is my universal "anyone can do it" investigation sequence for a non-starting Briggs, and I think Funzo is not the only member it can be useful to.

From the workshop manual, it seems to me that Briggs treats the Pulsa-Prime as a throwaway carburetor. They tell you briefly how to clean it, and that is all they have on it. If that doesn't work, you are supposed to get a fresh one.

Hi again everybody, I replaced the jet in the correct orientation as shown by bigted. Don't know if it was that or something else, but I just started up my mower a few minutes ago! and so far at least there is no hunting. I'm very happy and would like to say a HUGE thanks to grumpy and bigted for your help and advice!!

Thanks for reporting back on that Funzo, you've given this thread a conclusion, which makes it useful to others in the future. I think you can be fairly confident you had the jet in the wrong way, and have now corrected it.

I do think you'll be better off if you secure the speed-control Bowden cable to the carburetor though, so the cable inner won't end up kinked. A cable tie is simple and effective.

I'll close this thread.