Likely either the engine is flooded or low compression.
A simple go no go compression test is remove spark plug and press a thumb or finger firmly over the plug hole and crank engine. It should forcibly push your finger and make a loud PFFfft sound. No or little sound equals insufficient compression.
If the push rod was not bent, there was no reason to replace. If it was bent then I question how you set proper valve lash with new pushrod as the typical cause for a bent rod is a displaced valve guide.
If compression is OK then likely it's simply flooding and you have a carb float/inlet needle issue. Crank engine, remove plug and if it's saturated with fuel then it's flooded and a flooded engine will not fire, even with starter fluid.
Question edited for clarity and spelling.
Question moved from Motorcycles category.
Please proof read before pressing 'Post Question'. Your 'Bolson' doesn't exist!
https://www.google.com/search?q=Bolsen+1.5HP+158cc+briggs+%26+stratton
Surging is usually caused by an air leak in the inlet manifold.
Remove and sharpen the blade. If the blade is sharp, it will slice though the grass with no resistance. Over time, the cutting edge gets blunted by stones, grass and soil. If that doesn't fix it, remove the carburetor, strip and clean all the jets. Make sure you count the turns and write down any pilot jet settings.
Check the fuel lines. My brother had one that wouldn't start because when the fuel line was forced on to the fitting, some rubber shaved off the inside of the tubing and blocked the fitting. Also inspect the fuel filter and fuel cutoff or check valves if these are present.
I haven't looked up your particular model, but some riding mowers have fuel cutoff interlock devices. Check those for proper operation.
BRIGGS & STRATTON ENGINES:
For temperatures above 40? F use an SAE30W oil. Using multigrade oil may increase oil consumption. Using SAE 30W oil below 40? F will result in hard starting and possible engine
bore damage. For temperatures below 40 ? F use
an SAE10W-30 or SAE5W-30 oil. Oil capacity for the 6 H.P. engine is approximately 5/8 quart (20 ounces; 0.6 liter).
Refer to Briggs & Stratton engine owner's manual for additional
information.
Question edited for clarity.
Question moved from MISC.
Put the switch on the positive supply to the coil.
Or find out what was faulty in the original set up?
It's goose is cooked. or notsee long play below.I assumed that was done first,.or the blade engage lever is disengaged now and the engine pulley to blades is relaxed, the engine may have cracked the rod or crank shaft.
Rotate the engine in the direction it runs, since the stroke sequence is intake, compression, power, exhaust, the exhaust valve will open and close followed closely by the intake. After the intake opens and closes there will be a pause before the exhaust opens and closes again.