Briggs and Stratton Piston Ring Question

Hello


I’m currently rebuilding my Briggs and Stratton riding mower engine 31C707-0026 G1 100916ZDI and now I cannot get it to start. When I’m cranking the engine over it’s back firing very loudly and producing a lot of white smoke as well as spitting a lot of oil from the valve cover. During the rebuild I made sure that the two dots on the cam shaft and timing gear were lined up correctly and there are no broken crankshaft keys or flywheel keys. I purchased a leak down tester last night and ran 100 PSI at TDC (compression stroke) The results were about a 15-18% leak. Hissing could be heard coming from the breather tube which was connected to the intake tube as well as hissing could be heard coming from the dipstick tube when I removed the dipstick. I took measurements of the bore from the top, middle and bottom with a telescoping gauge and measured with a dial caliper with a result of 3.563in which matches appropriately with the service manual. So at this point I’m thinking that this has to be an issue with the piston rings and causing blow by. I did purchase a new piston during this rebuild (p/n 594539) and I am fairly certain that I followed the instructions correctly with making sure the paint lines were to the right of the gap and making sure to use the correct ring for the center ring. I also made sure that no ring gaps were lined up with each other upon placing the piston back in. Did I miss something? Are the gaps suppose to be at a certain position on the piston (center ring at 2 o’clock position 8 o’clock position, etc) ? What am I missing?

I’ve adjusted the valves several different ways with the same results. Adjusted the valves at TDC minus 1/4”.. Adjusted each valve one at a time while one was fully opened and adjusted the one that was closed. Valves were between 003-007 (what ever the service manual specs were. Don’t currently have it in front of me) even tried both valves at .004.. The push rods are indeed moving when I turn the flywheel clockwise. I did check the coil gap and was set to the specs in the book also via feeler gauge. Tried swapping new carb out.. same
Results.. fresh fuel.. same results.. shot some starter fluid in and got same results.. spark plug gap is good.

As you adjusted valves both ways, 
 
Just an FYI, quote "Adjusted the valves at TDC minus 1/4”.."   
 
If setting valves with the 1/4" it should be AFTER TDC (compression stroke). 
This is because of the compression release on the cam which opens right before TDC..
 
(The 1/4" is measured after placing a screw driver down the spark plug hole and measuring as the piston goes PAST TDC).
 
You adjusted with one valve tight and one loose, so that is fine....
 
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