Surging motor on NEW carb!?

[slomo]

both carbs surge in a similar way, one dies when you manually choke it (the new one)

And I hope it was puffing black some out the muffler? Or at least look like she was running rich/er at the moment?

while the original one does have a spot where it smooths out, when almost totally choked, right before you kill it.

Both carbs need to check fuel flow INTO the needle/seat FROM the fuel inlet tube. Remove the needle and let the fuel dump into the bowl area WITH the bowl off. Make sure the carbs CAN accept gas. While doing this, confirm you have a fat flow FROM the fuel line AT the carb inlet tube.

So this suggests that thew new carb is just bad

New carbs have to be gone through, making sure everything works as normal. You don't just pull your credit card and EXPECT a new Chinese carb to work like an OEM carb. That means make sure she accepts gas as above. FLOAT HEIGHT is proper. Nearly everyone misses this critical step. Does it have all the parts it is supposed to have?

And the replacement carb was only $9 so maybe I'll "splurge" on a $16 carb

NOW you are on to something. Do NOT buy the cheapest ad on Scamazon or Fleabay. Don't even look at them. Buy the ad that is at least $10.00 OVER the cheapest listed ad. $20.00 even better. I've had better luck with China carbs doing this. You still have to go through it once it hits your porch.

 

[slomo]

Fuel flow is great, I know this because every time I switch carbs, plenty of fuel flows nice and freely.

Okay, make a youtube video showing us all how much fuel flow you have at the carb inlet. LOVE to see this.

Also confirm it will drain the tank if you let it flow enough.

Lastly show the flow that comes out of the carb inlet and needle that would normally dump into the carb bowl. Pull the bowl and get to filming please. Make it rain.........

 

[slomo]

I'm hoping its not a valve/carbon issue,

I'm telling you it is time to de-carbon. Download your engine manual and read about it.

Neglect this and chunks of carbon WILL flake off, get between the piston and bore, scratching the heck out of the bore. THIS carbon is where all the bore gouging comes from. Then comes all the oil drinking and smoking.

Also means it's time to do a valve job lapping the suckers in. Head and block area where the head sits needs lapped as well.

 

[Forest#2]

Also I noticed when looking at the posts (8 pages) that the 1st carb was running lean (needed some choke) and the 2nd $9 China carb was running rich (choke made it worse)
The carb jets were swapped but still same symptoms.

You took a chance on a China $9 carb and struck out.

If none of the other stuff suggested brings it around:
You might have to just hump up, bite the bullet, roll the dice and try CHINA again. (I've had to do such, I've felt your pains)
That same carb came with at least 3 different jets, so hang onto your old carb jet, you might have to install it into another 3RD OR 4TH CHINA carb
If you buy them from Amazon you can usually return bad carbs for a full refund if you will keep a heads up about such when purchasing and do not expect a really cheap CHINA carb to last very long even it it works when received. I've seen the China carb bowls turn to solid rust on the inside in a years time using non-ethanol gas and they will not survive on ethanol gas at all.

If buying another carb do as previously suggested and pay little bit more for CHINA made STUFF. I suspect some of the sellers that offer the really cheap CHINKO carbs know they are selling inferior stuff.

I've had better luck with the HIPA carbs, but again it's a roll of the dice and disgusting even when it's know that carbs are actually bad and cannot find a good CHINA one.

 

[slomo]

I've had better luck with the HIPA carbs,

HIPA carbs are good. Still go through it making sure it will work as normal.

 

[l008com]

So, the recent developments above have me leaning towards the new carb just being bad. With that in mind, today I just had a few minutes to work on the machine but I really had to get my lawn mowed today. So I figured F-it. I took the new carb off, I cleaned the old carb for the 3rd time, poking out all its holes and whatnot, then I threw it on there and figured, if the original carb could keep the motor running with the air filter on, then maybe I'll just mow my lawn with it. It did, so I did. I half filled the tank with gas and a generous dose of seafoam and just started mowing. It surged a lot but it smoothed out on thick grass (under load). And as I went around, it seemed to improve over time. Its FAR from "fixed" but it ran a lot better by the end than it did at the beginning.

The pictures of the original carb weren't in this thread, I think that was something I first posted to reddit. It was covered in corrosion and the consensus was to just replace it. Of course at the time I didn't realized these carbs were so old that they're basically impossible to get anything but garbage replacements. But what can ya do. I didn't know this mower was THAT old when I started anyway. 27 years, I figured maybe 20 years. I think I'm still better off with a new carb if I can find one that actually works.

 

[Forest#2]

So, the recent developments above have me leaning towards the new carb just being bad. With that in mind, today I just had a few minutes to work on the machine but I really had to get my lawn mowed today. So I figured F-it. I took the new carb off, I cleaned the old carb for the 3rd time, poking out all its holes and whatnot, then I threw it on there and figured, if the original carb could keep the motor running with the air filter on, then maybe I'll just mow my lawn with it. It did, so I did. I half filled the tank with gas and a generous dose of seafoam and just started mowing. It surged a lot but it smoothed out on thick grass (under load). And as I went around, it seemed to improve over time. Its FAR from "fixed" but it ran a lot better by the end than it did at the beginning.

The pictures of the original carb weren't in this thread, I think that was something I first posted to reddit. It was covered in corrosion and the consensus was to just replace it. Of course at the time I didn't realized these carbs were so old that they're basically impossible to get anything but garbage replacements. But what can ya do. I didn't know this mower was THAT old when I started anyway. 27 years, I figured maybe 20 years. I think I'm still better off with a new carb if I can find one that actually works.

Hump up
AND
GET ER DUN

You did good.

 

[Auto Doc's]

At this point, it sounds like the culprit is the carburetor but make sure the mounting gasket(s)/ seal are in very good condition also. Also verify the spark plug gap is .030 inch and it is a good brand. If it is a Torch brand plug, throw it away (They are generic garbage)

In the fuel I prefer a tablespoon (1/2 cap full) of Marvel Mystery Oil mixed in the gas on push/ self-propelled mowers. (It's the original fuel additive) I've used it without issues since I was a kid starting out in the early70's working on equipment.

Read the history on Marvel Mystery Oil. IT was developed for Marvel brand carburetors many years ago when fuels were very unreliable.

Marvel Mystery Oil - Wikipedia

en.wikipedia.org

 

[slomo]

At 27 years old, way past time for a de-carbon, valve job, lap head and adjust valves. Get to work.

 

[l008com]

Carb #3 is very promising! I only ran a short test because it was 930pm But it seemed to be running MUCH smoother. Not perfect, but pretty good. I'll do a full lawn mow with it next week and then I think I'm going to finally call this one done.