Hi

I have a Hyundai 510sp lawnmower that is surging and I cannot figure out why. I've changed the carburettor, installed new gaskets, checked the fuel hose and filter, installed new air filter. Governor arm and spring looks fine. Still surging and driving me crazy.

Longshot, but could it have anything to do with the pull cord rapidly deteriorating and breaking?

I'm going to guess a little on this one, because I'm not sure of the age and model series you have.  I reckon if you remove the four allen screws from the side cover, you'll find the adjusting arm on the front roller frame has slipped down behind the plastic adjuster plate. 

While in there you should be able to see why it's not driving, probably pink gear behind the pulley has failed.

Some images would be handy if possible.

Hi Paul, and welcome to TGMF.

No worries on the first post thing, this intro board isn't compulsory but here should you wish to say hi. 

Sorry folks. I have just realised I posted a question already on the introduction section, without saying hello. Very rude sorry!
Hi 

I have just bought a Qualcast Suffolk Punch 35s on FB marketplace, it runs well however, the big drive wheel is slipping and the mower seems to be 'digging' in to the lawn. I have tried adjusting the height but it seems to make no difference. It is not the most even lawn, so could that be it?
I would really welcome some advice.
Thanks 

mick. Seems as though they are doing something. Seen some new pros and used pros with cut outs on the roller frame by the non chain end roller bearing. You know what this is for?
And have you seen the new seals? From the part drawings the end caps are new as well. Probably just got holes in for the seals to be screwed.

Hardys 50L Multi Purpose Compost - Potting & Seed Compost for Outdoor Plants | All Purpose Indoor Plants Potting Compost | Nutrient Rich Fertiliser for Garden, Pots, Planter Beds
Price on Amazon #ad https://amzn.to/3QLn71G

𝐅𝐎𝐑𝐌𝐔𝐋𝐀𝐓𝐄𝐃 𝐅𝐎𝐑 𝐇𝐄𝐀𝐋𝐓𝐇𝐘 𝐏𝐋𝐀𝐍𝐓𝐒 - Ideal for house plants and garden use, our compost is rich in non-recycled organic matter, supporting healthy plant growth, and strong roots. Perfect for sowing seeds, potting, rooting cuttings, and soil enhancement.
𝐒𝐋𝐎𝐖 𝐑𝐄𝐋𝐄𝐀𝐒𝐄 𝐅𝐄𝐑𝐓𝐈𝐋𝐈𝐒𝐄𝐑 - Formulated to optimise plant growth, this compost serves as a rich seed compost and houseplant compost. The slow-release feature ensures plants indoor and outdoor receive balanced nutrients, promoting vibrant growth.
𝐀𝐋𝐋 𝐒𝐄𝐀𝐒𝐎𝐍 𝐔𝐒𝐄 - A perfect soil for plants indoors and potting compost for outdoor pots. It can be used all year round for houseplant composting, gardening applications, and in your hanging baskets, or plant pots indoor as compost for indoor plants.
𝐄𝐂𝐎-𝐅𝐑𝐈𝐄𝐍𝐃𝐋𝐘 𝐏𝐀𝐂𝐊𝐀𝐆𝐈𝐍𝐆 - Our potting soil comes in eco-friendly packaging, making it a sustainable choice to support nature. From a top soil for garden to houseplant compost, our multipurpose compost has a rich colour and perfect sowing texture.
𝐌𝐔𝐋𝐓𝐈𝐏𝐔𝐑𝐏𝐎𝐒𝐄 𝐔𝐒𝐄 - Our compost is perfect for flowers, fruits, vegetables, shrubs, cuttings and more. Whether you need top soil for your garden, potting mix for indoor plants or soil for pots plants outdoor, our compost is the ultimate solution.

Price on Amazon #ad https://amzn.to/3QLn71G

Hummm, tried disconnecting the coils earths, in case it was the diode unit. Big spark! But after reconnecting, still sparked?? ight look closely at the ignition switch..
Then looked at fuel and it appears that the fuel pump had a siezure, but is now supplying, so had it running for a minuit. Grass is cringing with fear for tomorrow!
Also have a Countax with the three cutter deck, some progress with that on ignition, so will look at fuel next, though I had cleaned the carb recently..
SG

Thanks Mick
I will go over the fuel system and try fresh plugs.
SG

With my walk behind B&S powered also u/s at the mo, I am beginning to think sheep might be an idea....

Hi Shortgrass24, and welcome to TGMF

Those Honda's are notorious for coils dying, but like you said not normally both at the same time unless there was a major wiring fault on the machine.

As you said, the thin wire from each coil does the job of stopping the engine when grounded.  That wire is split into three via a diode module between the coils.

The engines are also very fussy on spark plugs, I have seen plugs that spark on one engine and not on another. So if it hasn't had a new set for a while I would try that first before throwing money at coils. Also make sure it's getting fuel, especially as it's not been run for so long.