"I can tell you what caused the engine to BLOW. It seem that B&S didn't do a good job of fastening the SCREWS that hold the butterfly inside the carb. They rattle loose and get sucked down the intake into the cylinder. That it turn gets smashed against the head by the piston and from that point on you're in trouble. Look at the piston and see if there are tell tale "Screw thread" marks on it. Of course B&S isn't going to admit it, but I had it happen TWICE." This happens periodically but is not common. PLUS, the piston smashing the screw into the head will not break or cause the engine to throw a rod. You are right, the screw will embed in the soft aluminum of the piston and the head. By the way, B&S does not make the carbs. The screw coming out of the carb butterfly may cause the engine to over speed resulting in failure unless the engine is shut down immediately. Most common cause of current B&S engine throwing a rod is carb float needle leaking, people don't check the oil when they start the engine and the oil contaminated with oil causes failure, oil not checked before starting and being low on oil OR just plain old not changing oil when it should be. Walt Conner

Thanks for your input folks and sorry I haven't replied before now - had ticked the box "send me an email when you get a reply" and hadn't seen any sowas thinking I had no replies. I can't help but think that fuel shut off issue is the culprit as I checked the oil level before and it was fine - after the engine blew it was low - thought it must have flung some out but this makes more sense. What sort of $s are these motors in the US? - I wa\s quoted a "special" price of $1100AUD for a 15.5 Intek from localshop but there is one on ebay locally for $847 - details are 15.5HP OHV Premium Intek series. Model 31E677.0133.B1 with the std. universal 1" shaft. The deck is 42" and while I have 1 1/4 acres there';s lots of gardens so nota big job - only went with 42" as it was a good deal swcond hand - or so it seemed :( Thanks for your help & any more suggestions much appreciated - Graham

Well actually, it is starting to make sense now. You slowed the hot engine and it stalls with a stuck valve. This keeps the engine from turning over easily but you took care of that with a pipe wrench. Now you have a bent push rod OR a broken rocker arm. So if you remove the valve cover and find that to be the case, why did the valve stick OR the valve guide may have worked up to where the valve keeper hit it. Either way, you need to check the cooling shroud for obstruction, the most common cause is overheating due to plugged heating shroud. Some people say that Ethanol fuel is causing this but I have no experience with that happening. IF the valve guide has worked loose, B&S says there is no fix except a new head. Well I have a fix. A stuck valve you can fix and buy a new push rod or rocker arm. Let us know what you find. Walt Conner

Yep, last year my tractor did the same thing! And, i checked all of those things, and finally did the trick with the thin wire in the gas cap! Some years ago, a man made me a gift of his aging Wheel Horse tractor. Said it had those same problems. I tried it out, and sure enough, i hadn't run it more than 3-4 minutes, and it stopped running. Of course, i opened the gas tank cap, and made sure it had plenty of gas, at least enough to run. Started it up again, and in 2-3 minutes--bingo--it quit. Removed gas cap, looked in, plenty of gas, put cap back on, ran for 2-3 minutes and--same thing! And then, it dawned on me--open the hole in the gas cap! I did, and problem fixed! I opened the hole in the gas cap, and it was fixed! I offered to give it back, but he said to keep it.