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Donald, Small Engine Technician
Category: Small Engine
Satisfied Customers: 1767
Experience:  I have 25+ years of experience repairing 2 & 4 cycle engines
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Deere L120 riding mower with 20HP Intek Twin engine all of a

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John Deere L120 riding mower with 20HP Intek Twin engine all of a sudden is knocking very loudly and has lost much power and keeps shutting down.

Hello. Thank you for choosing Just Answer. My name is***** will be happy to assist you.

Ray, did our problem occur suddenly?

If you fully depress your brake / clutch pedal, does the knocking noise still exist?

Customer: replied 10 days ago.

To confirm, you are hearing the noise regardless of the position of your brake / clutch pedal?

Is your engine a Briggs and Stratton engine?

Customer: replied 10 days ago.
It worked perfectly yesterday.....started today and the loud knocking really surprised me.
Customer: replied 10 days ago.
20 HP Intek Twin

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.

Customer: replied 10 days ago.
Come on, I am not a mechanic.. The noise is very loud metal to metal. It dies after a short while, smokes a little, has very little power . It is 13 years old and has been used to mow about 3 to 4 acres.
Come on, you are the mechanic

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.

Customer: replied 10 days ago.
In other is dead or dying or whatever a mechanic says.
Something is broken, for sure, as the sound is rapid metal to metal.

I agree. Something is either loose or broken.

Customer: replied 10 days ago.
OK, do you think it could be anything, say less than $500.00 to fix, counting pick-up and delivery. Or do think it could be much more, like a new engine at what $$$$$.
Just need your input and your experience...not holding you to your answer, just need your opinion.
Customer: replied 10 days ago.
The tractor is 13 years and has more than a 1000 hours on it.

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?

Customer: replied 10 days ago.
Oil was changed a month ago....I have checked it regularly.

Ok ...

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.

Customer: replied 10 days ago.
No, I do not hear the clanging noise.

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.

Customer: replied 10 days ago.
I hear the clacking. It is not constant but very loud at times.

This leads me to believe that our problem has to be on the outside of your engine, like a pulley or pto clutch, etc.

Customer: replied 10 days ago.
Is that good news? Is there anything else we can do over the internet?

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.

Customer: replied 10 days ago.
OK.....what is next?

Does you mower have a lever to engage your blades, or do you pull out a button?

Customer: replied 9 days ago.
pull 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?

Customer: replied 9 days ago.
I will try ....frankly, I don't know what the clutch looks like and where it is located.

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.

Customer: replied 9 days ago.
OK, I am learning. I see it now but have a hard time loosening the nut as the whole thing turns. I will get it off with someone to help.
As I have researched this problem now, I am 98% sure it is the clutch.
The new clutch assembly prices range from $120.00 to almost $300.00 for John Deere part #GY20878.
To have our local JD dealer do this, I can easily see a $600.00 price with the labor.
I will get back to you as soon as I get the clutch removed.

If you have an impact wrench, or if you can borrow one, you can loosen, and remove the bolt, without your engine turning.

Customer: replied 8 days ago.
Hi Donald, I am back.
Finally got the clutch off, engine is still clanking.....very loud click every ten to 20 seconds. Now what?
It is not a constant clacking.....every ten or so seconds, a loud clank.

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.

Customer: replied 8 days ago.
No, it seems fine.
Customer: replied 8 days ago.
someone suggested that it might be the muffler that a possibility?

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.

Customer: replied 7 days ago.
left off.......engine starts
right off......engine does not start

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.

Customer: replied 7 days ago.
Did we not eliminate internal engine problems a while ago?

Valves are considered external.

Your engine have definitely failed on your left cylinder.

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