Piston doing engine

Most likely cause is the fuel injectors are leaking, what ks the make model and year of the vehicle

Those are usually the symptoms of blow-by. This is frequently caused by worn or broken piston rings, damaged cylinder walls, or (infrequently) a severely damaged piston. Blow -by is pressurized air from above the piston (that is, in the combustion chamber) leaking into the crankcase and escaping wherever it can; the oil fill opening, the crankcase vent air inlet, or the dipstick tube are the usual places where it is noticed. It generally indicates relatively major engine problems.

Nope, this is most likely a problem with the valves needing adjusting. On your engine, there is a compression release that works off an arm on the camshaft. This mechanism is active at low RPM's and cancels out when the engine begins running. Many,many users have encountered this problem. The compression release AIDS in the starting phase. It uses the intake valve (which opens slightly) just below TDC on the power stroke in the 4 stroke cycle. The Briggs site has all the valve clearances and the instructions on how to do this. You will have to remove each valve cover (4 little screws) to access the upper valve train on your engine. You will need a box wrench, an allan or Torx (star) driver and a feeler gauge. It is not hard to do. You won't have to buy any new parts either. Here are the Briggs instructions for adjusting the overhead valves on your engine.

http://www.briggsandstratton.com/engines/support/frequently-asked-questions/Servicing%20the%20valves/

If your model has say a Kohler engine, then the adjustment procedures are probably similar.
This WILL fix your "hard-to-start" problem.

The breather tube is there to eliminate a buildup of pressure in the gearbox. The pressure is blow-by, (compression getting past the piston rings). Normally only a bit of blow-by occurs. As the bike ages, the rings don't seal up as well due to wear and cylinder expansion deformities. Now the blow-by is becoming a problem. The air/fuel mixture getting past the rings is diluting the oil and actually raising the "oil" level in the gearbox. This puts the oil closer to the vent hose and the increased blow-by pressure carries some of the oil into the air box. What should be done is a fresh bore of the cylinder and new first oversize piston and rings installed. Then do an oil change. Also, have the shop re-seat the valves while the head is off. Now you have a new top end. The bike will perform better now. A less expensive "work-around" is to just change the oil more frequently to maintain proper oil level.

I have owned several including a 2000 that i drive everyday.They have all used more oil than i thought was normal ( about 3 quarts between changes).A new pcv valve will help, i dont belive there is a fix other than rebuilding engine.

First make sure your air cleaner is good and clean. Black smoke indicates lack of air and uncomplete burning of the fuel mixture. I don't like to recommend oil but you should be able to see what the manufature recomends in your manual.
any 15w/40 diesel oil is as good as another in todays world,toyota oil is one of the major oil companies anyway,if you stick to caltex esso shell ,bp any of the major oil producers you cant go wrong ,,even pensoil valvolene no worries Diesel engines require more frequent oil changes due to the carbon that escapes around the piston and rings while operating.

Sounds like to me that the motor is running way too hot which could cause detonation. This is cause by carbon build up on the piston crown still hot as a stove top, therefore, igniting any left over gas still on the piston. Also, it may be due to a bad kill switch connection.

Most likely slap in the cam will cause the piston to not move smoothly. You say frequently so I am assuming this is not the first time. With that year motor if it is the original it maybe cheaper just to find yourself a good used motor and swap it out rather than do a complete rebuild

change engine oil and filter every 3000 miles.if car is under severe conditions.like. long idling.dusty condition.short running conditions.not letting engine get operating temp.hot climate or temperature.the maintenance intervals said you can change engine oil at 7500 miles.if its not under harsh conditions.

the (example refuelling) the engine starts just don’t turn the engine (like a stall engine). It is becoming a frequent problem I discovered than if I put the moto in a high gear and push the moto by hand the pistons move a little bit and then the electrical start engine starts OK. What is wrong with the engine......... I know that some bikes do that (engine adjusts ??....) ,Nomally the starter has some trouble turning the crankshaft if one of the pistons is in TDP. You better check the state of your battery, because it could be weak.... another thing to watch out is the starter relay - could be a signal that this part it's going for a looong vacation ,,,