Small Engines (Lawn Mowers, etc.): ohv17 no crank/start, compression release, fire suppression

Question
Hello,I have been reading your q/answers and this question is close to some others.
I have a Huskee tecumseh ohv17 hp rider. Last shut off made a loud pop and now will not start. I have adjusted valves to several different settings per  some other answers ,the starter and solenoid are new and the battery is charged. The only time I get the engine to turn over at all is when the charger is hooked to batt and I select the 75 amp quick start setting . Some other q/answers lead me to believe I have a compression release valve adj. setting problem ,but I am stymied at this point and grass is high!
Thank you for any help.
Joseph

Answer
Compression release is usually a lobe on the camshaft.  If all was running fine and then it backfired and quit running it could be a couple things.  Is there after fire suppression?  There would be a wire coming out of the bottom of the nut holding the carb bowl on.  If there is the part could have failed.  It shuts off the fuel when the ignition is interrupted.  I take it you have checked timing and the flywheel key, right?  

You said that the engine will only turn over if a charger is attached to the battery.  There has to be 12.6 V in the battery to start the engine.  If there isn't it will not turn the engine long enough to start it.  If there is no click the selonid is not operating and there is a problem in the start circuit. Seat switch fuse, PTO switch, brake or neutral switch, key switch, loose wires etc.  Some engines if you jump the starter you will damage the ignition.  So is there spark?  If not and the tractor side is operating it is the ignition system.  I assume you checked for a bad valve, push rod, keeper off, etc.  If the valves are not opening all the way the engine locks.  I am still thinking it could be timing. Let me know