briggs 12.5 Idle Surge HELP!

any ideas guys . icleaned the carbs and checked the plugs twice. and im still learning about troubleshooting the carbs a bit

Too lean.   
Low speed Jet, Pilot jet, whatever you want to call it... If it's a screw adjustment, go CCW until it smoothes out. If it's a brass jet, then use a torch tip cleaner to clean it out.
Could also be an air leak or you forgot to put in the air filter.
Good luck, keep us posted.

that didnt help . im starting to think its the governer. because when i hold the butterfly with my finger it runs smoothly . but when i dont it starts surging and going back and forth   

Still too lean.

When it surges like that, it's because it's not getting enough fuel from the low speed circuit, RPM's drop and the governor opens the throttle to compensate.
BUT nothing happens in that split second, so the governot opens the throttle even more. Enough so that it pulls from the high speed circuit.
By the time the motor gets enough fuel to start recovering, the throttle is way more open than it should be and the RPM's overshoot the target RPM. Then the governor closes the throttle and it happens all over again.

It's commonly referred to as "searching for fuel" where I'm from.

Does your carb have a low speed adjustment or a fixed jet?

Yeah it make sense the searching for fuel term . but heres a pic of the carb ive been fiddeling with that main screw tho only that one dont know of another one to move

Sorry Buddy, I forget what the idle circuit looks like so I can't help you other than saying that the screw in your pic should regulate the idle mixture to a certain point. It won't help if you've got a blockage elsewhere though...

The other screw obviously will raise the idle speed. Take 'er apart again and find the path for the low speed circuit and clean it again. Find the brass jet and clean it to the point of removing a tiny bit of brass. These carbs run lean from the factory usually anyway.

I backed off that brass screw at the back just a lil bit and it seemed to fix it . Is this good or bad ? Have mo idea what this screw is

If you backed off the screw you richened the air fuel mixture (if I'm correct) and yea that's good

Now I have 2 questions how can I keep this screw in place and No.2 my mower ran just fine is it normal for this to randomly happen   

It should have a spring on it to keep tension on it so it won't vibrate itself out when the motor is running. And it depends on a few factors. Bad gas can do bad things to a carb. It can make it run like crap. Type of fuel would have something to do with it as well. These new gases with the ethanol in it make my briggs run pretty bad and I have to put ethanol treatment in it then it runs great. I have cleaned everything on my carb a few times and tuned it and it still does it. And overtime a carb will need to be re tuned in order to make it run at it's best

so this morning i put a pin sized drop of thread lock and now it stays in place and it runs great

you should still get a small spring for it. thread lock may have been a bad idea. i'd just go get a spring. hell, one from a ball point pen may work (the clicky kind of pen)

Yea thread lock isn't the greatest cause it could go in between the threads of the screw and block the holes for the fuel to pass inside the carb.

Dipshaw87 wrote:

Yea thread lock isn't the greatest cause it could go in between the threads of the screw and block the holes for the fuel to pass inside the carb.

then, well... were right back where we started... lol

yeah ill go check it at lunch. but i put it right at the top of the screw threads very little and right at the top because i thought it could clog things too lol

I wouldn't worry too much about the threadlocker. If you applied it to the outside of the screw with it assembled, I don't think it will wick in far enough to clog anything.

Willis is right about the spring though. It's the correct way to retain the screw.

i got a spring from a pen and i will try that lol

don't it already have one?

1997 Murray wrote:

don't it already have one?

lol, you're right! Looks like there is already a spring on there. If he loosened a different screw, that's not good.   

yeah its the second screw behind the main one

is it the pilot jet?

In your picture, the top screw shown is the idle speed. The second one down, at an angle is the pilot adjust screw. The smaller one just below and to the right is the pilot jet (I think). Have you taken out the jet to clean it?

yup its super clean