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Discussion Starter · #1 ·
I recently put a new field coil on my recently purchased 316. The pulley spins free when the motor is off. When I start the engine, the pulley spins. There is no belt or deck on the tractor. Should it spin free when its off, and should it spin while the engine is on with no belt on it?
 

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JD317, JD318, JD430GT
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I think you're ok. It should spin free anytime that the PTO is not engaged. I'm guessing that its just getting a minor nudge or airflow to cause it to spin. If you had a belt on, I don't think it would be spinning while running (until you engaged the PTO).

If you want to prove that, (with the engine off) put a piece of duct tape on to hold it. Then start and see. I'm guessing it won't take much to hold it still.
 

Kish JD 318/420/430
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Most of the PTOs since the 1970's do no spin freely when not engaged (braking is applied when no power is applied, to stop the attached equipment in a short amount of time). Required by the government due to many injuries.

https://ogura-clutch.com/pto-reasons-to-use.php

https://ogura-clutch.com/flange-mounted-assembly.php

I have a 1987 318 with Onan P218G, I can barely turn the pulley over because the internal brake is applied with no power on it.

Adjusting the 3 nuts on the plate to set the air gap, is also setting the brake pressure.
 

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From the 316 - 318 - 420 manual

Put a 0.46 mm (0.018 in.) flat feeler gauge through
slots in brake plate between rotor and armature. Turn
lock nuts until space between rotor and armature is 0.46
mm (0.018 in.). Be sure all three nuts are adjusted so
space between armature and rotor is adjusted to
specification at each of three slots in brake plate.
 

Intermediate MTF Member
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Discussion Starter · #11 ·
At .018 its spins like a breeze. When I set it at .012, it started to rub a little, but I could still spin it with 2 fingers. Do you think the brake surface is just really worn out?
 

Kish JD 318/420/430
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CantKeepUp, TM (Technical Manual) for the 317 is TM1208 and the PC (Parts Catalog) is PC1698, I was at my local dealer today picking up my parts order and they were clearancing a ton of old manual @ 1/2 off the marked price which was 1/2 off the original price. Saw some 1XX, 2XX, snow mobile, seeders, planters SCUT, CUT, and some very large tractors (2 part - 4" thick) manuals. You might want to breeze down and check it out quickly at your local dealer.
 

Kish JD 318/420/430
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JD316Fan, yours may been worn down, a visual inspection (look at the rivets in the armature, is that part worn down onto the heads of the rivets) and some measuring (rotor) might be needed.
 

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Some early PTOs are not the clutch/brake design that is now common and will spin unloaded. I was just working on neighbors 317 and noticed the PTO would actually rotate the belt that was tied to the #4 JD logsplitter with engine running and PTO switched OFF. I thought there was a wiring problem but then tried to split a log which of course put some load on it and it stopped. I guess the leaf springs that pull the armature against the brake plate could also be fatigued.

I would adjust to the factory recommendations for gap, any tighter and you risk excessive wear.
 

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Some early PTOs are not the clutch/brake design that is now common and will spin unloaded. I was just working on neighbors 317 and noticed the PTO would actually rotate the belt that was tied to the #4 JD logsplitter with engine running and PTO switched OFF. I thought there was a wiring problem but then tried to split a log which of course put some load on it and it stopped. I guess the leaf springs that pull the armature against the brake plate could also be fatigued.

I would adjust to the factory recommendations for gap, any tighter and you risk excessive wear.
Same deal on a 79 314 I had
 
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