A few things will lead to a bent pushrod on these engines.
In recent years, there seems to be an increase in the frequency of this related to an intake valve sticking to the valve guide (your friend's bent pushrod is for an intake valve, right?). What happens is this: When the engine is shut down an intake valve may end up in the open position. The gummy, sticky deposits on the portion of the intake valve that is exposed to the induction draft of fuel and air from the carb are left resting inside the valve guide. As the engine cools, these deposits may solidify and act like glue, holding the valve in this position. Then, the next time the engine is cranked, the camshaft moves away from the open position but the valve stays stuck in place. As the cam moves further, the pushrod can fall out of the rocker cup and be caught on the edge of the cup. As the camshaft continues its course, it revolves back around to open the valve, only now the pushrod is on the edge of the rocker instead of deep in the cup. The effective result of this is that the pushrod bends when the valve has been pushed to total collapse. In the process, the intake valve springs free and leaves you without a clue of what took place.
To prevent this from occuring, you should add Marvel Mystery Oil to your fuel in the recommended amounts on the bottle. This leaves a thin film of clean lube on the intake valve stem that gets hit by the induction draft inside the intake plenum.
There is also the possibility that a valve seat might have come loose if the cylinder head hot really hot from a mouse nest inside the cooling fan shroud (and this should always be checked before returning the engine to service).
Another possibility is that the rocker arm stud has loosened in the head or the adjuster has backed off. If the engine was running fine the last time it was shut down and suddenly began running on 1 cylinder the next time it was cranked...........I would suspect a valve had stuck while it was stored.

Wow. Thanks for the info mownie. You seem to know your stuff. I don't know if it is the exhaust or intake (I'm not sure my neighbor knows) but from your description I'm guessing the intake. I'm not familiar with Marvel Mystery Oil. I may look into this for myself also. Does removing the cylinder head allow you to replace the rod or is more disassembly required?

It is not necessary to remove the head to rteplace a bent pushrod. You probably will need to remove, or at least loosen, the rocker arm. You really do need to determine whether the bent pushrod serves an intake valve, or an exhaust valve. This only requires a careful visual examination of the places where the exhaust manifold header bolts to the head, and where the intake manifold bolts to the head. The intake valve is closest to the intake manifold and the exhaust valve is closest to the exhaust header. If the bent pushrod serves an exhaust valve, you certainly need to remove the cooling shroud sheetmetal and look for a mouse nest that caused the cylinder to run very hot, which may have allowed the exhaust valve seat to loosen in the head. If it does end up being the exhaust valve pushrod......you will need to remove the cylinder head for a complete assessment of the condition of the head.
Marvel Mystery Oil has been around for a couple of generations now.
MMM can help reduce the chances of having an intake valve stick in its guide. Exhaust valves are not very susceptible to the circumstances that cause an intake valve to stick. The same valve surfaces that cause sticking on intake valves, operate under very different conditions on the exhaust valves. Whereas the intake valves surfaces run pretty cool being constantly "washed" in the induction draft stream, the exhaust valve surfaces are continually "blasted and scalded" clean by the extreme temps of the exhaust gases exiting the combustion chamber during the exhaust stroke. The high temps present in the exhaust valve environs tend to keep everything from sticking to the valve stem, thus....no gums to solidify and glue the valve to the guide.

When you have the valve cover off, check the height of the valve guides. Blocked cooling shroud/fins can also cause the valve guides to loosen and work up out of the head resulting in bent push rod from the valve spring retainer hitting the top of the valve guide. B&S says there is no fix for this, I have one.

Walt Conner

Hi Walt and mownie! I just noticed this thread. A few minutes ago I posted this on the other forum ...

"I have the 24hp briggs els mod 446777 as discussed above in a recently acquired cub tractor/mower showing 105 hrs. It has the notorious yellow clip air filter housing. Previous owner did little or no maintenance. Started with oil smoke, ran rough. Compression showed 120 left cylinder, 60 right cylinder. Removed valve cover right cylinder, intake rod broken and 1+1/2 inch piece missing, exhaust rod bent lying loose. Exhaust valve guide was pushed toward the valve retaining washer so the rod bent when the valve retaining washer hit the guide. I was able to tap the guide back to a position approximately the same as the guide on left cylinder.

The intake valve guide seemed fine and both valves are moving freely.

Hope that's clear. Looking to understand the cause and proper repair.

Any ideas and suggestions? TIA"

From reading this thread I 'm guessing there may be two separate problems with intake and exhaust.

I'm interested in your fix Walt. I haven't pulled the head yet, and if so do you recommend doing both heads at the same time? And it's always a balancing of cost versus value. The rest of the machine was never abused, but obviously the engine was never taken care of.

Not necessary to bother the other head. Most frequent cause is over heating of the head due to plugged cooling shroud and or fins. There was one brand of mower that the mfg. ran the exhaust too close to one of the cylinder head and caused this.

Valve guide will not stay in place once it has come out with out fix. B&S says there is no fix. Instructions for valve guide fix at address below, put in proper format.

Walt Conner

Well might have helped if I had actually put an address.

Walt Conner
wconner5 at verizon dot net