Small Engines (Lawn Mowers, etc.): B&S 14.5hp OHV I/C mower hard to start, fly wheel, jumper cable

Question
My B&S is hard to start and getting harder each time,I usually spend about an hour playing with connections, batteries etc and eventually it starts, once running it runs fine,  If I take the spark plug out it turns over relatively easy, once replaced only turns a bit and then appears like a low battery. On checking the solenoid,I disconnected the small wire and jumped power from battery & the engine tries to start same as initial attempt. shouldn't this had only make the solenoid click. I did notice after a few attempts of trying to start smoke coming from the solenoid. Also could valve clearance be causing this, might they need adjusting. P.S I have not touched the engine, I have only cleaned electrical connections and check spark plug. Any advice would be appreciated.
Col

Answer
The solenoid is smoking due to high resistance. The underlying reason could be many. With the spark plug removed you have created a much less resistance (Due to lack of compression). The most common causes are as follows. 1. Faulty connection, due to either it being loose or dirty. make sure all connections are good. Or try running a jumper cable from the negative side of the battery to a good ground. This avoids your other ground. 2. The solenoid I would think is good if it is getting hot and smoking, shows current is passing through it. 3. Is the battery fully charged and holding a good charge? 4. The starter could possibly be  weak, which makes it unable to spin during a load being placed on it, but strong enough to spin with the load removed from it. Only way you'd know for sure is with a load meter to check the amperage being drawn during starting. 5. Flywheel shear key could have a partial shear and it is fighting timing, check fly wheel key. 6. Compression release system may be hanging up not releasing the cylinder compression while in the starting mode casing a compression lock within the combustion chamber. ...... You'll need to do further testing, and diagnostics...Tom