Manual PTO Clutch Rebuild and Set Screw Removal Tips
Posted: Sat Jan 22, 2022 2:19 pm
Hi Folks,
The release fingers on my 123's PTO clutch were worn out, so I decided to rebuild it. I had a parts clutch assembly and with a few new parts, I made one good one from the two. I like the overall design. I think it's cool that it's an actual clutch. But there is one big drawback as they get older: removing the set screws. They seize from rusting, which is bad enough, but worse is when some ham fist uses the wrong size Allen key or fails to dig out the dirt so the key fits, and they end up damaging the screw.
To remove mine, I started by digging dirt out of the screws with a pick, so that I could get an Allen key in. I then added some penetrating oil and returned to it the following day. One set of screws was completely missing, and there was only one locking set screw. (For those unaware, there are three special screws with pointed tips that are installed into the pulley first. These lock the assembly to the idler bearing. Each of these has a short flat nosed locking screw that is tightened in place over top, thus securing the bottom screw into place.) I manged to back one screw out far enough past the outer bearing race, but the other was stripped out and completely seized. Fortunately, it was seized partway up the hole, not in it's normal resting position, so it didn't impede me from gently tapping the assembly off of the crank.
So how to get that stripped, seized screw out?
Well, I thought about heating it with a torch but I was concerned about cracking or warping the pulley. I've also had poor luck drilling out these types of screws (maybe I don't have the right bits?), so then I turned to this: It used to be called Evapo Rust but now Rust Check is calling it Enviro Rust Wash. Long story short, it's hands down the best thing I've found to dissolve rust from iron and steel. So over the course of a week, I went out to the garage once a day and filled the set screw hole with this using an eye dropper.
At the end, none of my screw extractors would get a hold of the damaged screw, but I found a drill bit, that just barely did.
So very carefully, using a set of vice grips and the drill bit, I turned out the damaged screw. It actually came out easily! Yay! After that, it was relatively smooth sailing: parts were replaced, cleaned, painted, adjusted and assembled. I also replaced installed a new clutch basket/starter pulley as the old one had been damaged by someone. The story ends well. Almost. Once assembled, the clutch would release, but there was just enough drag that an implement (e.g. my QA-36) would not stop. I tried readjusting the clutch to no avail. Then I removed the three anti rattle springs, and presto! the clutch works fine. I believe the new friction disk and the new clutch basket/starter pulley are just a wee bit tight on clearance, so with the springs installed, they cause it to bind ever so slightly. When spring rolls around and It's had some run in time, I'll reinstall the springs and see if it's better. In the mean time, the clutch works like new, and I hope my story helps someone. Cheers!
The release fingers on my 123's PTO clutch were worn out, so I decided to rebuild it. I had a parts clutch assembly and with a few new parts, I made one good one from the two. I like the overall design. I think it's cool that it's an actual clutch. But there is one big drawback as they get older: removing the set screws. They seize from rusting, which is bad enough, but worse is when some ham fist uses the wrong size Allen key or fails to dig out the dirt so the key fits, and they end up damaging the screw.
To remove mine, I started by digging dirt out of the screws with a pick, so that I could get an Allen key in. I then added some penetrating oil and returned to it the following day. One set of screws was completely missing, and there was only one locking set screw. (For those unaware, there are three special screws with pointed tips that are installed into the pulley first. These lock the assembly to the idler bearing. Each of these has a short flat nosed locking screw that is tightened in place over top, thus securing the bottom screw into place.) I manged to back one screw out far enough past the outer bearing race, but the other was stripped out and completely seized. Fortunately, it was seized partway up the hole, not in it's normal resting position, so it didn't impede me from gently tapping the assembly off of the crank.
So how to get that stripped, seized screw out?
Well, I thought about heating it with a torch but I was concerned about cracking or warping the pulley. I've also had poor luck drilling out these types of screws (maybe I don't have the right bits?), so then I turned to this: It used to be called Evapo Rust but now Rust Check is calling it Enviro Rust Wash. Long story short, it's hands down the best thing I've found to dissolve rust from iron and steel. So over the course of a week, I went out to the garage once a day and filled the set screw hole with this using an eye dropper.
At the end, none of my screw extractors would get a hold of the damaged screw, but I found a drill bit, that just barely did.
So very carefully, using a set of vice grips and the drill bit, I turned out the damaged screw. It actually came out easily! Yay! After that, it was relatively smooth sailing: parts were replaced, cleaned, painted, adjusted and assembled. I also replaced installed a new clutch basket/starter pulley as the old one had been damaged by someone. The story ends well. Almost. Once assembled, the clutch would release, but there was just enough drag that an implement (e.g. my QA-36) would not stop. I tried readjusting the clutch to no avail. Then I removed the three anti rattle springs, and presto! the clutch works fine. I believe the new friction disk and the new clutch basket/starter pulley are just a wee bit tight on clearance, so with the springs installed, they cause it to bind ever so slightly. When spring rolls around and It's had some run in time, I'll reinstall the springs and see if it's better. In the mean time, the clutch works like new, and I hope my story helps someone. Cheers!