Hello Costa Rica 2
It certainly sounds like you may have a ring problem. It could also be that your cylinder head is carboned up and there is carbon built up around the valves. You may also have wear in the valve guides or you may have a loose valve seat. Is the motor very old? You could get an idea of compression by taking out the spark plug, putting your thumb over the hole and spinning the flywheel. The compression should be enough to pop your thumb off the hole.
You probably should pull the head off the motor and take a look at the cylinder. Check for any scoring or wear on the cylinder walls. Check to see how much movement the piston has from side to side in the cylinder. Check to see how much carbon is built up around the valves and in the cylinder head. Pull the valve or breather cover off and check the valve clearances. You should have about .007" on the intake and .011" on the exhaust when the piston is about 1/4" past top dead centre.
If there is any damage to the cylinder walls you may find that replacing the motor is the best option. However, everything else can probably be fixed if you are willing to try.
Let me know what you find in the visual exam and we can go from there as to the procedure etc. Do you have a Briggs and Stratton dealer somewhere near you to obtain parts?
All you have to do is clean off the end of the crankshaft and then remove the crankcase cover and the cylinder head. Note the timing marks on the camshaft and timing gear. Remove the cam shaft so you can get at the rod cap. Make sure you mark the con rod and rod end cap on one side with a centre punch before removing. Rotate the crankshaft to get at the rod cap bolts. Remove the bolts and rotate the crankshaft to push the con rod and piston up the cylinder. You don't need to remove the crankshaft from the motor. Push the piston out the top of the cylinder. Make sure you mark the exhaust side of the piston if it is not already marked. Remove the old rings. Check the new ring in the cylinder and check the end gap. Make sure the gap is within specifications.
Install the new rings in the order specified. The rings should come with directions as to which ring is which and which way up they go. If you have a ring expander all the better for installation. Check the cylinder. Do not hone the cylinder as it is an aluminum bore. You will do more harm than good.
I think you may run into a problem with installing the piston back into the cylinder if you don't have a ring compressor which is small enough. Install the piston with the marked side to the exhaust. Be careful with the rod as you come through the cylinder not to bang anything or scratch the cylinder. Be careful not to jam the rod onto the crank. Replace the rod end cap matching your marks. You will need some lock tight for the rod bolts. Apply the lock tight and torque the rod bolts to 100 inch/lbs. You will need a small torque wrench to get in the tight fit. Re-install the cam shaft matching timing marks. Clean off the crankcase and fit new gasket. I usually just grease the gasket first. I usually replace the pto seal if I've had the cover off. For the price it saves putting it back together and then having to pull it apart again cause the seal starts leaking. Once the new seal is in then replace the crankcase cover being careful of the governor mechanism and the oil slinger. As you re-install the cover, keep an eye on the timing marks. Some of the motors have a tendency to jar a little when the cover is almost on and this kicks the timing gear over one tooth. The cover bolts should be torqued to 90 inch/lbs. Replace the head gasket and torque head bolts to 150 inch/lbs.
Hope this helps. Let me know if you need part numbers or anything.
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