The piston will not go down - Hoisting

Check band # 175520 (black rubber band around the outside of the cylinder) is what causes the piston to retract. If the check band is in place, then problem could be caused by cracked lower bumper, worn piston oring or cylinder seal on the headvalve. IF the cylinder seal is bad, air will leak between seal and the top of the cylinder and could push piston down cylinder. If piston oring is too loose, the piston will not stay at the top of the cylinder. If you point the nose of the gun up then down again and the driver moves within the cylinder, replace the oring. Good luck

Set the piston to TDC (top dead center) this is the higest point the piston will rise before moving on to the down stroke, either by lining up the marks on the crank rotor or a long screw driver (large handle so it wont fall in) down the plug hole and watch for the highest point lock or hold at this point. The cams should be fitted next on the 'compression' stroke meaing the all valves should be closed when the cams are seated (no valves being pressed by cams) generally at this point the cam lobs face away from the valves, next stroke down (ignition of fuel) valves should be closed with the exhaust cam moving round ready to rock on to the exhaust valve as the piston rises to the top again (4th stroke exhaust) as the exhaust valve lobe rocks off the intake cam lobe should be starting to rock on opening the intake valve on the down stroke of the pistion.
Trun the engine over by hand to make sure no valves are knocking the piston.
Should be as follows
1. all valve clearance free/rocking at ' TDC 1st 'down' stroke (ignition of fuel) valves closed exhaust moving round but not pressing valve ,
2. 2nd stroke 'up' exhaust valve rocking open and closing as piston tops with the intake ready to rock on as the exhaust closes and piston tops (exhaust),
3.3rd stroke 'down' (intake of fuel) as the piston moves down the intake valve should be opening.
4. 4th stroke 'up' compression of fuel all valves rocking closed as the piston rises for the compression stroke back to TDC all valves closed/rocking free.

Intake, compression , ignition and exhaust. (**** squeeze bang blow)

Hi,
The compression stroke is when the piston is traveling UP and the intake and exhaust valves are both closed.

Intake: Piston going down, intake valve open, exhaust valve closed
Compression: Piston going up, intake and exhaust valves closed
Power: Piston going down, intake and exhaust valves closed
Exhaust: Piston going up., intake valve closed, exhaust valve open

squeeze the rings tight against the piston and slide the cylinder down over the top off the piston. you can use WD40 to help slide it down smoother. once the cylinder is in place, hold it in place with one hand and push the kick lever down to make sure the piston slides up and down the cylinder smoothly.

two stroke mowers will have a picture of a oil can on the fuel cap,if it doesn't it is most likely a four stroke.
four stroke mowers will have a fuel cap and a oil cap as well.

two strokes fire every time the piston gets to the top ( every two strokes of the piston, down, up)and the fuel in and exhaust out is controlled by holes in the barrel called ports, they need oil mixed with the petrol to lubricate the piston and engine bearings.

Four stokes fire every second time the piston gets to the top( or every fouth stroke of the piston, down, up down ,up) the fuel and exhaust are controlled by valves that are pushed open by the cam, oil is pumped from the sump to the top of the motor and to the bearings for lubrication

1.****/air in,piston going down
3.squeeze/compresion,piston going up
4.bang/plugs fire,pistons going down
2.blow/exhaust.pistons going up
is that understandable??

piston should be flush with the barrel not going past the barrel. if piston hits the head it wont go back down so check if thats not your prob

If the timing was off, from my experiance, it would cause the valve to go down threw the piston. The rod more than likely was on its last leg before the repair. Because the timing actually keeps the crank shaft (that turns the rods/pistons up and down) and the cam shaft (makes the valves go up and down) in sequence. So if the timing were off then the valves would be down when the piston were up. This could cause the rod to break but usually it either cause the valve to punch a whole threw the piston or the piston to bend the valve. Either case is very bad but so is a broken rod.

Hope this helps

Hi,
Use (2). And you could back it off by 1/4 turn, rather than 1/2 turn I think. You want the piston to almost touch the screen at the bottom of its travel. You don't want the piston to push the screen out.

Fergus.