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Ranwell1, Small Engine Technician
Category: Small Engine
Satisfied Customers: 10304
Experience:  I Own a Lawn Mower Sales and service business (37years). Have 2-cycle and 4-cycle certification.
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I have a 316 John deere, When I turn the pto switch on it instantly

Customer Question

I have a 316 John deere, When I turn the pto switch on it instantly kills the engine. I have bypassed all safety switches, using jumper cables to attach power directly to the pto clutch, and it still kills the engine. I have went through all adjustments that I know of. I have adjusted the coil to make sure it isn't touching the rotor, adjusted the air gap to 0.18. I even bought a new coil and it does the same.
Submitted: 2 years ago.
Category: Small Engine
Expert:  Rex L. replied 2 years ago.
Let me ask this. Have you tried it with the belt off pto? If there is something froze up or blade stuck on deck it will kill the engine.
Customer: replied 2 years ago.
Yes, it does the same with or without the belt. I stopped putting the belt back on after the first few times because it is one less step between adjustments. I am a mechanic, and I am lost on this thing.
Expert:  Rex L. replied 2 years ago.
Make sure you have the seat switch bypassed like you say you do. It acts like there is a short somewhere in the system in the pto or in the wiring. But you bypassed the wiring with a jumper to the pto from battery. Acts like pto is shorted.
Customer: replied 2 years ago.
Yes, I ran a jumper from a seperate battery also, it still kills the engine. If I hook the hot direct to the pto lead and just tap the ground on the frame I can get the deck to run full speed, but as soon as it goes full contact it kills it. I agree it does sound like the coil is shorted. I ohmed it and it is 4 ohms. I think I read 3-4 ohms is good. I also checked my old coil and it is 4 ohms also. With just the coil on the engine I can power it up just fine. As soon as I put the rotor and pressure plate on is when it dies. I am not sure how much air gap there should be between the coil face and the rotor, I can't see where it has touched anywhere, and I have tried different shims. This is a mower that I did a engine swap on. The old kohler had something inside it that wanted out. It kept knocking but I didn't let it out. I put a 22 horse Honda clone engine on it. This clutch worked fine on the Kohler. The only thing different is the shoulder on the crank is futher out on this engine. I shimmed the coil out and didn't use the spacer that was on the end on the crank on the kohler.
Expert:  Rex L. replied 2 years ago.
Didn't know we were working on and engine swap. I will opt out and see it another expert has any ideas. 4 ohms should be correct.
Customer: replied 2 years ago.
Ok. Thank you
Expert:  Rex L. replied 2 years ago.
Have a good day
Expert:  Ranwell1 replied 2 years ago.
This problem is pretty simple to diagnose but next to impossible to fix.
The problem is that since the crankshaft on the replacement engine is different than the old one, it is locking up when you are assembling it. Spacing it out may not be the fix, you may need to get a different PTO, but which one is going to be very difficult to figure out. This is why we usually tell customers to only replace an engine with an exact duplicate of the one taken off.
You sill don't have the spacing correct.
I wish I had a better answer for you but this is all I have for you at this time.
Please let me know what you find.
Customer: replied 2 years ago.
It is not locking up. I have found measurements and everything is close enough to work. The problem is that the clutch is magnatizing the crankshaft, and that is messing up the magnetic trigger on the ignition. I am going to try to find a different clutch, and try to demagnify the crank.
Customer: replied 2 years ago.
Do you happen to know how I can remove this post?
Expert:  Ranwell1 replied 2 years ago.
No. it just stays up until it goes off buy itself, I think it goes off once you have given a good rating..
I have never heard of the crank getting magnetized.