Update on BS engine.........

I posted yesterday about a 24hp OHV Briggs engine that bent a pushrod.

I worked on it today. I didn't have a new replacement push rod, but I straightened the bent one and found it was 3/16" in diameter. I found a piece of steel brake line tubing that was 3/16" inside diameter. I cut a piece of the tubing an inch shorter than the push rod and tapped the push rod through it, leaving about a half inch on each end. I installed the push rod, set the tappets, and turned the engine over by hand with the spark plugs removed.

When that valve opened all the way, I heard a scraping sound of some sort, but the push rod held up. I spun it with the starter, and it worked OK. I put the spark plug on that cylinder and had good compression. I put both plugs in, held my breath, and hit the starter. It fired right up and ran like champ. I put it all back together and went out and mowed for a few minutes.

So, what happened? Beats he11 out of me, but I have a theory. Number one, the cooling fins had a lot of grass clippings in them, possibly causing the engine to run hotter than normal. Number two, both tappets on that cylinder were noticeably 'way looser than the other cylinder, possibly mis-adjusted at the factory. (I reset them the same as the other side).

My theory is, if the tappet was too loose and the engine running too hot, carbon built up on the valve stem until the valve would't open all the way and bent the push rod. The scraping sound I heard when I first turned the engine over with my reinforced push rod must have been the valve guide scraping carbon off of the valve stem.

Anyway, with the grass clippings cleaned out and everything else cleaned up, it's running like a champ. I'll buy a new push rod when I get a chance.

Great piece of creative shade tree mechanicing, even if I did do it inside in a well equipped shop.

i'm a Briggs dealer and your experience doesnt surprise me.

I had a problem with my B&S OHV 2 cyl. in a lawn mower bending the pushrod on one of the exhaust valves. Turned out the valve guide was pushed up out of the head causing the rocker arm to hit it and since the rocker wasn't going down the full distance it caused the push rod to bend. I replace the rod about 4 times before I saw what might be the cause on a small engine forum and sure enough it was my problem. I took it all apart and pushed it back in and used a small chisel to set it in place. No issues since then, been two years since "fixing" it in place.

It could have been a stuck valve, I've seen them push valve and guide up, and bend pushrod.

Amazing what one can accomplish with a little "shadetree engineering"! You are right about one thing, clean cooling fins are critical to an air cooled engine. Depending on the usage, it is good to remove the shroud and clean them with compressed air at least once a year. If used where there is a lot of dust and trash in the air, more often.

On mine IIRC I had to stake the valve seat, replace the push rods and drill and tap the rocker arm shaft bolts out to the next larger size.

I so a lot of small engine work. IMO B+S of today is nothing like the B+S of even 20 years ago. You have to buy their top of the line stuff to get a decent product and even then it's a gamble. There's a reason Honda has a better rep than B+S.