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Anyone with a rivera pro clutch ever go outside to pull the clutch, only to realize one or more of the four pressure plate stud nuts just spin when you try to remove it? When that happens, the pressure plate can't be removed and clutch removal as a whole is impossible.
Rivera uses four 5/16-18 button head screws for the pressure plate studs that run in from the back side of the steel inner hub, torqued in place using standoff nuts. Frequent removal of the clutch can loosen these studs over time, which is why rivera specifically states to:
"Dab some high quality anti seize on the stud threads of the pro clutch hub! This will prevent the nuts from sticking and cause the studs to come loose when the pro clutch is disassembled"
Sometimes they'll stick anyway. Primo has documentation on how to separate the bearing from the carrier HERE if you're up for making some tools and have a spare early belt drive basket. Below I outline how to do it using a steering wheel puller.
You'll need a steering wheel/harmonic balancer puller (like THIS) a rivera clutch hub puller, an impact, and a shop press to do this job.
First off, an exploded view of the rivera pro clutch for 36-84 big twins, model PC-1000-A:
And the assembled clutch on my own bike:
You'll need to first try and remove the spinning pressure plate nut with an impact. It really is the only way without using destructive techniques, aka a cutoff disc. I was able to zap mine off after a few minutes.
Now, for those of you just looking to just get on the road, you can try to lock down the spinning stud using a 1/2" socket on an impact, but no guarantees that the stud won't spin again when you try to take the clutch apart again down the line.
Once you manage to get the pressure plate off and the pack pulled from the clutch, use the primo hub puller to pop the clutch off the mainshaft.
Remove the lockplate from the rear of the basket, then take the clutch to the press and separate the hub and the basket. It doesn't take much to free the two and often times the hub will fall out once it's started, so be careful.
Once you have the hub free, you're looking at this:
Start by pulling the smaller circlip around the inner hub.
In order to access the button heads on the backside of the pressure plate studs, we need to separate the bearing carrier and bearing from the steel inner hub. This task is a major pain in the ass and took me a full day to sort the best way to do this without ruining the bearing carrier.
The best method for separating the bearing and hub is to use a harmonic balancer/steering wheel puller. To set the tool up, you'll need four 10-32 x 2" screws, and an assortment of washers to keep the small screwheads from falling through the slots of the tool. Using a 10-32 washer, then a 1/4, then a 3/8 stacked on top of each other works well. You'll need to find a piece of scrap to put between the puller screw and the clutch hub surface - I used a small piece of 1/4" scrap steel.
Here's a reference pic for setting up the tool:
In this image I am using the long puller screw that came with the harmonic balancer kit - however, I have found the screw that comes with the primo puller in the background works much better since it it has a blunt end, and they're both threaded the same.
Once the tool is tight over the clutch hub, start cranking on it, and be fucking careful not to pull any of the 10-32 threads, for christ's sake. Work it slowly, frequent removal and resetting of the tool will be required. Also, a big ass pair of channel locks clamped around the ears of the puller will keep the whole shebang from turning as you crank the puller screw. Using a little heat around the steel inner hub will help the bearing pop free easier. Once you've pressed the inner hub level with the bearing, use some wheel spacer stock or small sockets to finish it the rest of the way through.
If you did this right, you'll have the inner steel hub and bearing retainer separated with all your 10-32 holes intact and your retainer free of gouges.
In these pics we can see the hub and bearing separated, and the four 5/16-18 screws used for the pressure plate studs:
Now we remove the alloy splined outer hub from the steel inner hub by removing the two 1/4-28 x 1/2" screws (already removed in the picture), and the four 5/16-18 x 1-3/4" standoff nuts.
Taking a look at the inner clutch hub we can see why this problem persists and how it can be easily fixed. Primo, in their infinite wisdom, thought that simply running a bolt w a nut on it as a stud for the pressure plate would be a robust, long lasting design. In this image we can see that there are four 1/4-28 threaded holes (of which primo uses only two) to bolt the inner and outer hubs together from the front side, and four 5/16" through holes, of which the button head screws slide in from the back (why primo didn't just drill 17/64" and tap 5/16-18 to lock in the studs is beyond me):
To fix this problem, we're going to reassemble everything using spring steel ribbed lock washers under the button heads of the studs:
Since I've got everything apart, I'll be replacing everything with stainless hardware. Primo uses 1-3/4" long screws for the pressure plate studs - I found that even though the addition of lock washers adds minimal extra stack height, the clutch studs are already bordering on too short when using 1-3/4" length screws. I recommend going to 2" long. I also added two additional 1/4-28 screws to fill the holes primo didn't use, and the six 10-32 screws for the lockplate. When running the standoff nuts on the 5/16 screws, use a shitload of red locktite and an impact.
Here's a pic of the inner and outer hubs reassembled:
Here's an image showing adequate clearance after the lock washers are added:
Now that the inner and outer hubs are assembled, you can move forward pressing the bearing back on. Be careful, don't fuck this up:
Take it out the press, make sure it all spins smoothly and is fully seated:
Now install the hub back into the basket - if you marred or gouged the bearing carrier, make sure to knock down any high spots w emery paper or a fine file. Now is also a good time to sand the clutch pack steels if they're shiny.
Install the clutch per primo instructions and spew a shitload of anti sieze of the pressure plate studs. Tighten the stud nuts so that they bottom and then just a little more, the lockplates will prevent the nuts from backing out so don't go crazy here!
Rivera uses four 5/16-18 button head screws for the pressure plate studs that run in from the back side of the steel inner hub, torqued in place using standoff nuts. Frequent removal of the clutch can loosen these studs over time, which is why rivera specifically states to:
"Dab some high quality anti seize on the stud threads of the pro clutch hub! This will prevent the nuts from sticking and cause the studs to come loose when the pro clutch is disassembled"
Sometimes they'll stick anyway. Primo has documentation on how to separate the bearing from the carrier HERE if you're up for making some tools and have a spare early belt drive basket. Below I outline how to do it using a steering wheel puller.
You'll need a steering wheel/harmonic balancer puller (like THIS) a rivera clutch hub puller, an impact, and a shop press to do this job.
First off, an exploded view of the rivera pro clutch for 36-84 big twins, model PC-1000-A:
And the assembled clutch on my own bike:
You'll need to first try and remove the spinning pressure plate nut with an impact. It really is the only way without using destructive techniques, aka a cutoff disc. I was able to zap mine off after a few minutes.
Now, for those of you just looking to just get on the road, you can try to lock down the spinning stud using a 1/2" socket on an impact, but no guarantees that the stud won't spin again when you try to take the clutch apart again down the line.
Once you manage to get the pressure plate off and the pack pulled from the clutch, use the primo hub puller to pop the clutch off the mainshaft.
Remove the lockplate from the rear of the basket, then take the clutch to the press and separate the hub and the basket. It doesn't take much to free the two and often times the hub will fall out once it's started, so be careful.
Once you have the hub free, you're looking at this:
Start by pulling the smaller circlip around the inner hub.
In order to access the button heads on the backside of the pressure plate studs, we need to separate the bearing carrier and bearing from the steel inner hub. This task is a major pain in the ass and took me a full day to sort the best way to do this without ruining the bearing carrier.
The best method for separating the bearing and hub is to use a harmonic balancer/steering wheel puller. To set the tool up, you'll need four 10-32 x 2" screws, and an assortment of washers to keep the small screwheads from falling through the slots of the tool. Using a 10-32 washer, then a 1/4, then a 3/8 stacked on top of each other works well. You'll need to find a piece of scrap to put between the puller screw and the clutch hub surface - I used a small piece of 1/4" scrap steel.
Here's a reference pic for setting up the tool:
In this image I am using the long puller screw that came with the harmonic balancer kit - however, I have found the screw that comes with the primo puller in the background works much better since it it has a blunt end, and they're both threaded the same.
Once the tool is tight over the clutch hub, start cranking on it, and be fucking careful not to pull any of the 10-32 threads, for christ's sake. Work it slowly, frequent removal and resetting of the tool will be required. Also, a big ass pair of channel locks clamped around the ears of the puller will keep the whole shebang from turning as you crank the puller screw. Using a little heat around the steel inner hub will help the bearing pop free easier. Once you've pressed the inner hub level with the bearing, use some wheel spacer stock or small sockets to finish it the rest of the way through.
If you did this right, you'll have the inner steel hub and bearing retainer separated with all your 10-32 holes intact and your retainer free of gouges.
In these pics we can see the hub and bearing separated, and the four 5/16-18 screws used for the pressure plate studs:
Now we remove the alloy splined outer hub from the steel inner hub by removing the two 1/4-28 x 1/2" screws (already removed in the picture), and the four 5/16-18 x 1-3/4" standoff nuts.
Taking a look at the inner clutch hub we can see why this problem persists and how it can be easily fixed. Primo, in their infinite wisdom, thought that simply running a bolt w a nut on it as a stud for the pressure plate would be a robust, long lasting design. In this image we can see that there are four 1/4-28 threaded holes (of which primo uses only two) to bolt the inner and outer hubs together from the front side, and four 5/16" through holes, of which the button head screws slide in from the back (why primo didn't just drill 17/64" and tap 5/16-18 to lock in the studs is beyond me):
To fix this problem, we're going to reassemble everything using spring steel ribbed lock washers under the button heads of the studs:
Since I've got everything apart, I'll be replacing everything with stainless hardware. Primo uses 1-3/4" long screws for the pressure plate studs - I found that even though the addition of lock washers adds minimal extra stack height, the clutch studs are already bordering on too short when using 1-3/4" length screws. I recommend going to 2" long. I also added two additional 1/4-28 screws to fill the holes primo didn't use, and the six 10-32 screws for the lockplate. When running the standoff nuts on the 5/16 screws, use a shitload of red locktite and an impact.
Here's a pic of the inner and outer hubs reassembled:
Here's an image showing adequate clearance after the lock washers are added:
Now that the inner and outer hubs are assembled, you can move forward pressing the bearing back on. Be careful, don't fuck this up:
Take it out the press, make sure it all spins smoothly and is fully seated:
Now install the hub back into the basket - if you marred or gouged the bearing carrier, make sure to knock down any high spots w emery paper or a fine file. Now is also a good time to sand the clutch pack steels if they're shiny.
Install the clutch per primo instructions and spew a shitload of anti sieze of the pressure plate studs. Tighten the stud nuts so that they bottom and then just a little more, the lockplates will prevent the nuts from backing out so don't go crazy here!
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