I have a John Deere model LX172 riding mower. It runs well but I can't get the mower to engage. The main pulley under the motor will not turn. The engine will kill if I turn on the PTO switch while not in the seat so I'm assuming the switch and the safety part of it works. Any suggestions on what to check first? In laymans terms.

Thanks,

See my article on the 155C. Did you take the seat off and visually check the safety switch.

The switch looks fine. I have it taped down now so it thinks I'm on the seat at all times. I only see one set of wires coming from the clutch which has a junction to the wires that run up to the PTO switch. Everything looks fine. I can't find a fuse anywhere if there is one.

It still could be your pto switch it runs the electric clutch and the safety system runs there also
'it has different wires going through it for each.just because it kills the engine means the safety is working doesn't mean its getting power to the clutch,turn the switch on and check for power at the clutch ,

I have examined the ssfety swith, pto switch, and all wires leading from each and everything appears to be fine. Is there a way to actually know if the safety swith or the PTO switch is working?

Hi,
Check the blue wire(s) for voltage at the PTO switch. Also, try sitting on it with the ignition switch on and turning on the PTO switch (engine not running) and the clutch should clunk.
Peace,
Clarke

The only wire in the PTO switch I seem to have any voltage from is the black/yellow wire. I have tried a brand new PTO switch but that did not work either. When I turn on the PTO switch with the engine off, I hear a click near the ignition but that is it.

If you hear a click that sounds like your pto is working,sounds like you have a belt problem ,check and make sure the belts are both tight,

Even if the belt was loose, shouldn't the main PTO pulley at the bottom of the engine be spinning? It doesn't move.

Try tightening the bolt for the pully under the engine then start it sounds like the bolt is lose

Probably need to check the air gap on the pto clutch

How do I check the air gap? I have tighted the bolt until it turns the engine but that didn't work either. The bolt itself is spinning when the tractor is running but I just can't get the PTO pulley to engage with it.

The spring loaded bolts on the clutch is how you set the air gap,
There should be a little window by each bolt,use a feeler gauge and set at about.015 go inbtween the two plates.

I have removed the PTO clutch and had it tested. It works fine. I have replaced the PTO switch but that didn't help. I have looked over all the wires and fuses but I don't find any problems. I now have an electrical schematic of my tractor but I really can't follow those. I'm trying to figure out where in the system I'm losing power. I test fine at the battery but nothing at the clutch. Any advice on what to check or in what order to find my problem. I know it's electrical somewhere.

Hi !

I have those same troubles with my LX172. Did you find the problem ?

Thanks

Hi,
One unusual thing that the LX172 was prone to was having the four engine mount bolts back out and breaking the engine to frame ground. The engine could be seen to shake distinctly to and fro as it came to a halt if this was present.
Peace,
Clarke