Bowtie: I adjusted the intake valve on the right cylinder, clearance was off a little. Loss of compression can result from several things. Most common with this type of engine is the valves "stretch" over time and do not completely close.They could also be sticking some, bent, or have a small piece of carbon on the seat; all of which can create a "leak" in the cylinder. If you've never done a valve adjustment, it can be both tricky, and dangerous to the engine if not done correctly.Tolerances are measured in the thousands of inches. My best suggestion would be to get a friend to show you how to do this. Or, get a service type manual from your public library, preferably with pictures. Either way, double check every move; and the final clearances, or you can ruin the engine in a matter of seconds.

A "cylinder leak down" test (or reasonable facsimile) using compressed air can be done to identify the route by which the compression is escaping. To do a "bona fide" leak down test requires a "percent of leakage gauge". A close approximation of the test can still be done if you have (1)Compressed air available, and (2) a threaded adapter fitting that will screw into the spark plug hole and also receive an air hose, (3) a means of securely locking the crankshaft/flywheel in the "TDC of compression stroke" for the cylinder to be tested. Locking or holding the engine from turning when compressed air is applied to the cylinder is very important, both for personal safety, and, for accurate test results!! Actual testing is simple and amounts to listening to determine where the air is escaping when compressed air is applied to the cylinder through the spark plug hole adapter fitting. As follows: Turn the crankshaft/flywheel to position the piston of the testable cylinder to TDC of the compression stroke. Here's a hint, the valve train for both valves of that cylinder will place the valves in the closed position. you determine this by watching the tappets through the open valve compartment (if applicable) or by watching the valves with the valve cover removed. When both TAPPETS or lifters, are retracted toward the camshaft, and you can detect clearance between the end of valve and the tappet.....lock the flywheel in place so the crankshaft can't turn when air pressure is applied to the cylinder. Failure to securely lock the flywheel against moving could result in personal injury if the crankshaft rotates in reaction to the compressed air applied to the cylinder. In addition to the locking of flywheel, keep your hands away from the flywheel and crankshaft until air pressure is disconnected from cylinder. With the flywheel locked securely, thread the adapter fitting into the spark plug hole (threads are 14mm dia. X 1.25 pitch when you ask for the adapter fitting) and tighten it so it can't leak air. Connect the air hose from a source of compressed air (60psi to 90 psi recommended). IF, there is a loss of compression, you will hear air leaking from somewhere. Carefully determine where the air is escaping by using a 2 foot length of hose or tubing. Place one end of the hose or tube close to an ear (but not inside your ear) and then move the other end of hose to the exit portal of the exhaust system. If air is heard loudly escaping here, the defect is in the exhaust valve or seat. Check the intake valve condition by moving the end of the hose to the throat of the carb (throttle must be held wide open, choke butterfly open, and any crankcase breather hose must be disconnected from the carb, if carb is mounted to the intake manifold). If air is heard loudly here, the defect is in the intake valve or seat. If you do not detect air escaping from either of those places, check to see if you can hear air escaping from the crankcase breather hose (or pulse hose if impulse fuel pump is present). If you hear air escaping from the crankcase breather hose, or pulse hose, the defect is in the piston or cylinder wall. Always remove the compressed air supply from the cylinder before unlocking the flywheel. A leaking head gasket serious enough to cause loss of compression would be obvious without any test equipment, and you know it right away when the engine is running.

Old thread, let us fast forward to update it: Briggs now intentionally makes plastic carb throwaway small engines called Briggs EXi or "Just check and add oil" engines... No small Briggs for push/self propelled mowers have an iron sleeve now, not even Pro model engines have it anymore.. According to Briggs site there is none being built today, what iron sleeved engines left on the shelves is all there is left!! Pro 850 was the last to have it. All Kohler engines are made China. Briggs Vanguards are made in China. Kohler's head gaskets still fail (fixing my sons 3 yr old cub now) & also suffer oil seal leaks from poor machining today, all are made from cheap grade materials in China and won't last long anymore! Very soft aluminum & plastic abounds them. Regardless where anything is built it's made by people who never even knew nor do they care about our American pride or our history of quality or about the products longevity! Anyone 30yrs old and under today simply grew up replacing products not repairing them unless they were dirt poor like I was and always tried repairing first but hey it was the 60's and everything had nuts/bolts/screws then and was steel. So why would today's engines have so many problems only after a few yrs running when they once ran for many decades without majors? Well' it's called "Planned Obsolescence" and its a fact most corps have now adopted this. Google it to really understand it well if you never heard of it, you'll be so thrilled. So everytime I read about engines online I'm really glad I'm a pack rat and keep everything. Well' I keep stuff until problems show up so I still have my 76 B-100 8 speed Wheel Horse tractor with the cast iron Kohler K series engine. It's engine/trans has never been apart once and not reached its first ring job yet & if it ever does I'll never worry about it again in another 30+ yrs or in my lifetime at least. It still burns no oil and cuts just as good as anything today without any of the mechanical problems. Why people keep buying these junk newer mowers again & again instead of buying the old brutes for a fraction of the cost that have outlasted them all by several decades idk? Restoring these if needed, is a lot cheaper than new mowers now days and it's an all new cast iron brute again ready for decades of service! I see some very nice cast iron garden tractors on craigslist all the time. Real garden tractors because GT used to actually stand for Garden Tractor but now it's just a sticker slapped on them and they can't even run anything, example: My Wheel Horse runs 23 different implements including Generator, side sickle, snowblower, tiller etc... Visiting websites about old Wheel Horses, old JD's & old Cubs (non MTD) tractors etc..and everyone is bragging & very proud of their mowers longevity and still use them regularly, sold or scrapped their newer ones they bought just after a few yrs usage. Been there done that with a Husqvarna myself! Visit any site like this one about newer mowers and what you'll always find is its junk, its in the shop, motors bad after 3 yrs, hydro rear ends out second time around. I'll sue them all! Lemon Laws anyone??..ect.....lol Even the expensive Zero turns have very costly engine/hydro repairs I read about them and have friends who own them too. In fact I'm good friends with people who care for football fields and cemeteries here so I hear first hand but they are very fast cutters while they are problem free, rarely make a complete season without a shop visit though. Expensive upkeep no doubt. Sorry but its just ignorant to me to pizz away money for landfill delight. Simply amazing and very sad for the old crying indian too. Now that really shows my age huh? *Peace

Well Fish says to check that the rocker arm studs are tight in the head. If that doesn't turn up the problem, check the height of the valve guides. I take it the engine is doing this on the same cylinder, same valve? Sometimes the valve guide comes loose on these and work up until the valve keeper hits the top of the valve guide bending the push rod. This is not repairable according to B&S. Some have been having problems with the valve sticking in the guide causing push rods to bend. IF your "unrepairable" valve guide is the problem, email me for fix. Walt Conner wconner at verizon dot net