Surging Lawnmower

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I have a Hyundai 510sp lawnmower that is surging and I can't figure out what's wrong. I've cleaned the carburettor about 5 times with carburettor spray and enlarged the 2 valves slightly with a micro drill bit. All the little holes are clear. It was fine last year but I did leave fuel in it over the winter.

Should I just buy a new carburettor?

I didn't know about Hyundai lawnmower reputation before I bought it (second hand).
It's driving me crazy
 
The engine surging is usually due to carburettor issues, as you suspect.
Can I ask you which valves you enlarged please?
A new carb could be the way to go - often the Chinese replacements are astonishing value for money.
John :)
 
I'll try to describe them, the brass one above the emulsionfying pin and the black one on top, that you need to remove the throttle limiting screw in order to remove. Is you can tell, I'm no expert

Yes, a new carburettor is £25, free postage. So very reasonable
 
It seems like you have dealt with the slow running jet ( that’s the one on the top of the carburettor) and the emulsion tube....that one deals with revs up to 3/4 maximum then the main jet fully takes over.
If you have an air line you could have another go, but I’d really go for a replacement carb here - but please use new gaskets too.
John
 
carburettor it is! Yes, I've added the gaskets to the cart already. Thanks for your help
 
Turns out it's not the carburettor. Any other ideas, or is pushing it off a bridge best?

PLEASE!
 
Have you altered the governor rods and springs in any way.......bent them or stretched them?
I'm assuming that you are getting a good flow of petrol from the tank -- no blocked filter or collapsed hoses?
Try turning the spring loaded idle screw in a bit - just to get a fast tickover - and come back.
John :)
 
The rod and spring looks fine to me.

The filter in brand new and the hoses don't look collapsed.

If the idle screw is the bit on top of the carburettor that the rod is connected to, there's no screw, it's rivetted on

Do you think it's worth me removing the fuel line to check there's nothing blocking in there?

Thanks
 
Ignore the idle screw comment, I found it but no difference

Fuel hose looks clear
 
Sorry, I meant air filter. Haven't touched the fuel filter. Should I?
 
Sure.....some makes have a filter in the fuel feed pipe, others have a fine gauze filter in the tank itself and nothing in the pipe.
If you can give us a pic if it’s the former that would be good!
John
 
It's one of these, I saw the end when I took the hose out. I'll see if a quick wipe will do the job, the grass really needs cutting this weekend
1000015075.jpg
 
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