Small Engine Troubleshooting Problems? Ask a Mechanic Now.
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Ray, did our problem occur suddenly?
If you fully depress your brake / clutch pedal, does the knocking noise still exist?
To confirm, you are hearing the noise regardless of the position of your brake / clutch pedal?
Is your engine a Briggs and Stratton engine?
You and I need to do some troubleshooting. I would begin by removing both valve covers, to see if your valves are opening and closing.
Also, you can remove both spark plugs, and spin your flywheel by hand, to see if you hear the noise.
I understand. Due to the fact that I cannot see or here your engine, I have to ask troubleshooting questions, and make suggestions. You could have a broken piston rod, or your pto clutch could be at fault, but it takes troubleshooting steps to make the correct diagnosis.
With your help, I do believe we can figure it out.
I agree. Something is either loose or broken.
If the problem is internal, then it will be best to replace your engine. The cost of parts, labor, plus pick up and delivery would likely exceed $500.00
I do not like to spend money unless necessary. Our problem could very well be something that is very simple.
Have you checked your oil? Does your oil smell burnt?
I would like for you to try something that is simple.
Remove both of your spark plug wires, to prevent your engine from starting. Turn your key to start position, and let's see if you hear the noise as your engine spins.
Hopefully this tells us that our problem is external.
Put your spark plug wires back on, then lock your parking brakes. Start your engine and let's listen for the noise.
This leads me to believe that our problem has to be on the outside of your engine, like a pulley or pto clutch, etc.
I am back with you.
Yes, this will be good news, if we confirm that our problem is not your engine, but is something that is attached to your engine.
Does you mower have a lever to engage your blades, or do you pull out a button?
This tells me that you have an electric pto clutch. Only one bolt holds it in place. Can you remove it at some point, then start your engine, and listen to hear if the noise still exists?
Your pto clutch is on the very bottom of your engine. It has a pulley on it, that drives your deck belt. It has wires connected to it.
If you have an impact wrench, or if you can borrow one, you can loosen, and remove the bolt, without your engine turning.
Thank you for checking. Next, remove the plastic engine cover from your engine. Start your engine, and let's see if your starter gear is sticking in your flywheel.
You stated that your engine has lost power. Let's try something. Start your engine and allow it to run for up to 10 seconds, then shut it off. Next, remove the spark plug wire from your left cylinder, and try starting your engine, to see if it will start with one spark plug wire off. If your engine does start, shut if off and put your spark plug wire back on, then repeat this same procedure on your right cylinder.
Thank you for checking. This helps to narrow down our problem. If your engine will not start after you remove the spark plug wire on your right cylinder, this means that your left cylinder is at fault.
Remove the valve cover on your left cylinder. Let's see if both valves are opening and closing.
Check for broken push rod, or loose rocker arm, etc.
Valves are considered external.
Your engine have definitely failed on your left cylinder.