I'm sure one of the professionals will be along shortly to answer your question.

I don't know anything about the nature of these.

If after you get done adjusting, if the nut ends up in the same relative spot as the last time, I'd guess, it's turning on the stud while running. This could be caused by the nut expanding more than the stud, when hot, and becoming loose. A Nylok nut might help or if there are enough threads, it could be double nutted.

You need to locktite the threads on the stud, remove them and clean them with carb spray and their holes, as they
are coated with oil.

Fish

along with Fisher recommendation IMO I would get a new nut, rocker arm, and push rod. I would also look at the threads on the rocker arm stud for wear. Clincher locknuts are deformed at the end to hold it tight on the threads, fiber or nylon clincher nuts IMO would not be recommended for High temp useage. I would go with orginal replacement parts see if that corrects the problem.

The rocker arm stud was not ever loose, just the nut. The stud, nut and set screw were all well cleaned before applying Locktite to the nut. The nut was/is an OEM part. It did not appear the rocker nut is a locknut. The rocker arm and push rod appears fine (no wear, bending, or cracks). Thanks for the ideas!

bobg

The clinch type locknut is a good idea along with medium strengh ( blue ) Loctite to be sure. Loctite dosn't expand when it sets. If the old nut split it was just bad.

If that dosn't work you can always look for aftermarket nuts and studs. It doesn't seem as if the OEM Briggs parts are all that high quality. A rocker stud and nut is something that should last the life of an engine...

Permatex makes a 'Surface Insensitive', Blue medium oil resistant threadlocker, for oily threads.
Made just for me to dribble on a drop to lock things for a bit.

If there is enough threads double nut it Or jam-nut it as suggested by tmajor. you would adjust the first nut to get you clearance within limits and then hold that nut and tighten the second nut up against the first nut to create a lock so neither one will work loose.

In the picture in this link you can see the set screw being tightened which is part of the rocker arm nut. There is no room for an additional nut.

bobg

Here is a link that might be useful: {{gwi:352618}}

That picture, in part, doesn't make sense to me. I don't understand how you can torque the nut to a predetermined figure. ... what does it torque against?

A "star washer" under the nut might help, however, I don't know how it would affect the torque situation or the seat on the rocker arm.

I'd get a NEW adjusting nut. The old one MIGHT be too worn to maintain tension.

Valve lash is adjusted with the piston 1/4" PAST TDC.

Are your push rods bent/bending?

I'd be a bit concerned that the cam lobe or lifter might be getting "eaten away" where they contact each other. Any unusual, visible metal particles in the oil?

Same engine as the-
"Craftsman Lawn Tractor -briggs stratton 2004" thread!
?????

Borrow a dial indicator and measure the cam lift at the rocker. The exhaust and intake should be the same. If not, your cam could have a soft lobe, which is wearing down. You should also inspect the rocker itself, as it could be soft as well. These parts are heat treated, and if they miss the step they will wear quickly.

The thing is that normally stuff like this shows up right away and in the first year of operation. Normally not on a four year old machine.

Running(starting really) much better! Found that in addition to the valve problems I also had gas leaking into the cylinder. Reading about others having this problem, the needle valve/seat/float is the likely cause. It wasn't gummed up and these parts were moving freely. The needle valve looks ok. What I did find was the cheap plastic float was the issue. On the float there is a small lever that pushes on the needle valve. Looking at this closely and watching it engage as the float travels I noticed this small plastic lever was bent. Hard to say if it was always bent or what bent it??? Anyway, replaced the float (wish there was an equivalent metal float instead) and it is running without gas leaking in after several days of rest.

I think when I was dealing with the exhaust valve adjusting this drained any gas that was in there, thus I did not know I had this problem too. At the time the gas that came out was not much and I thought do to my hand turning of the engine. Even though this took a long time to fix and was a pain, I did learn a lot, though I'll stick to my day job. THanks to all responded :)

bobg