B&S 18HP single clinder hunts

[Freezzman]

B&S Inteck 18hp single cyl hunts seems to run OK for 10 -15 minutes then aggressively hunts .
New Gas, tank clean
New carb and filter
New Plug
Checked gas cap for venting (OK)
set governor and replaced spring (set Static adj) Ides fine max rpm sounds OK
Happens when I use the tractor for lawn fertilizing with a trailer tank (small) and sometimes mowing
If I engage the blades RPM's seen to level out momentarily when spraying
Thanks
Freezzman

 

[mechanic mark]

B&S OEM carburetor? Post model xxxxxx, type xxxx, trim xx, code xxxxxxxx from engine, thanks Mark

https://www.amazon.com/Briggs-Stratton-697241-Carburetor-Replacement/dp/B008TSVEF0/ref=sr_1_1?hvadid=616863258234&hvdev=c&hvlocphy=1015319&hvnetw=g&hvqmt=e&hvrand=190281390915728905&hvtargid=kwd-30105021492&hydadcr=26611_11715043&keywords=697241&qid=1687126583&sr=8-1

Walbro Carburetor overhaul kit above, OEM B&S Kit

 

[Freezzman]

Hi Mark will get the info today
And Thanks for Helping

 

[Freezzman]

B&S OEM carburetor? Post model xxxxxx, type xxxx, trim xx, code xxxxxxxx from engine, thanks Mark

Hi Mark Hope this helps
Carb
Walbro -mexico
0812
696181
Engine
Model 31H777
Type 0202
El 0204262A
18HO Intek Plus
Family YBSXS.5012VP 274B26
could be a 5

 

[Freezzman]

Hi Mark Hope this helps
Carb
Walbro -mexico
0812
696181
Engine
Model 31H777
Type 0202
El 0204262A
18HO Intek Plus
Family YBSXS.5012VP 274B26
could be a 5

should be 18HP Intek plus

 

[Freezzman]

should be 18HP Intek plus

LMT 4993

some other number 64

 

[slomo]

Trash in the fuel tank. Flush it out then blow it out with compressed air. Verify good flow AT the carb inlet.

 

[Forest#2]

You say the carb is new Walbro LMT.

The Walbro LMT are NLA. (No Longer Available)

If you ordered a Walbro LMT replacement you probably received a Nikki and if the price is in the $20 range it's a China clone carb. They lead you to believe you are getting a true Walbro but that is not so. (and known for the issues you are having even when new)

Do you still have the original Walbro LMT carb?
The usually clean up really easy and then when re-installed adjust the idle jet.

Here is a link to carb info, repairing, etc.
Just select Briggs and then single cylinder Intek then you will see Walbro and then go back and scroll down to see the Nikki's.
https://outdoorpowerinfo.com/repairs/
Briggs started using Nikki's instead of the better Walbro's is why they are shown as NLA.. (and China clones the Nikki's and wht you describe with your engine is quite common with the Nikki's.

Also do as suggested by slomo and add a Briggs red fuel filter and replace the fuel hose. If no fuel filter is installed your carbs are going to take in trash AGAIN. Also use NON-ethanol fuel.

Just another hint to keep in mind:
That link above WILL NOT do you any good if you are going into a China clone replacement $20 Nikki because it's probably got the wrong jet plus it's just wrong China thing. You just have to suck it up and get another carb assuming the intake gasket at the manifold is good and also the plastic manifold is not cracked.

 

[StarTech]

Two different replacement carbs depending on the date code.


You need the 792358. Superseded to 594593. List for $120.

Also if you brought a clone then that is likely your problem as the last two customers did the same and I had to re-jet the carbs. Also did you replace the intake manifold gaskets? Especially the one at the cylinder end.