Hi There, Hoping I can get some ideas here of what to try next go get my Craftsman riding mower starting. The engine on it is a Briggs and Stratton 21 HP model 331877. Here's a summary of what it's been doing and what I've tried/checked so far: First off, when I tried getting it started this spring I remember the starter was turning the engine very well, but it didn't want to start up and after a bit of cranking the battery died. Eventually mower started after jumping it from my car, but it took quite a bit of cranking. But the starter was having no problems turning the engine over. Since the battery was probably around 5 years old I replaced it along with changing the oil, new air filter, new oil filter, and new spark plug. Now after doing all this the mower has been cranking really slow. Even when jumping from my car. Even with the car engine running and getting ~13.5V at the mower battery terminals. I had some corrosion on the ends of my battery wires which I scrubbed with a wire brush and baking soda. They look like shiny copper now but still it was barely cranking and usually got stuck I think on the compression stroke. I've tried a new starter and still had the same problem. Next I read about the intake/exhaust valve adjustments that sometimes need to be done for these OHV engines. I tried turning the flywheel by hand and I found that it turned easily for awhile, then I would hit a point where there would be lots of resistance (like I could barely manage to turn the flywheel by hand) and then another similar hard point right after. Then it would turn freely again for awhile and then those same two hard points again. One detail here is that when I manage to turn past these points of high resistance I hear what sounds like air being squeezed out (kind of like from a bicycle pump). Not sure if this this is good or bad, but maybe someone can let me know (like maybe it indicates the compression release is doing its job). So next I took off the spark plug and tried again. The flywheel turned very easily and using just the battery on my mower the starter could turn the engine over easily. Based on this I opened the valve cover, found the point where I had a bit of slack on the valve rockers, found TDC from there and turned the flywheel clockwise to move the piston 1/4" further. I found there was actually very little or no gap set, so I adjusted to 6 and 4 mils for the intake/exhaust. After closing everything up and putting the spark plug back in it was still the exact same problem, starter getting stuck on those same spots. Also I've sniffed the oil and no gas smell there. When I changed the oil I put in 1.5 quarts of Castrol SAE 30. Looking back at the manual I think it said it takes something like 1.3 or 1.4 quarts so it may be overfilled a tad - and there may have been a bit of old oil that wouldn't drain but probably not too much. I was trying to go by the dipstick and it was tough to read. But I know I put in exactly 1.5 since I have an extra half quart left over. And I just wanted to throw in that whenever I get the mower to actually run it seems to run great and starts very quickly once the engine actually turns over. The initial problem I had when it was cranking nicely was probably just that the fuel filter needed changing. So at this point I'm not really sure what to try next and I'm hoping to get some help/ideas here. Is the flywheel resistance I'm feeling normal? I was under the impression that there's a compression release mechanism that's supposed to make the engine easier to turn at low RPMs. But maybe easy for me and easy for the starter are two different things. Or could it be electrical problems and I'm just not getting enough current to the starter? With all this cranking it wouldn't surprise me if something in the starter circuit got fried (solenoid maybe?). Any ideas on what to test for and how to test it? I've checked the voltage at the starter and it's way low (like ~5V or sometimes less), but that may just because the motor is getting stuck. Anyway, sorry for the long post but hopefully the details help. Appreciate any help because this mower is driving me nuts.

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