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So I had been searching online like crazy lately on how to mod the left cover on a build I’m doing to run a foot clutch. There was two options I kept finding: one was through the cover that basically ended up with you having to use a wrench as the lever. The other was an expensive way in which you sent your cover to someone and they machine the parts you need and fit it to the cover. There were other various options too with drilling another hole in the cover for a lever or completely going around the cover with various linkage set ups but none of those appealed to me.
As far as the expensive way, it looks great and I have no doubt that it’s probably the most “bulletproof” way to go. My hang up was paying someone $200 for something I felt I could do without a machine shop. As for the “wrench” way, I’m sure it works fine but I just didn’t like the idea of a wrench just hanging off of a bike that I put a lot of time and effort into to make look nice.
So my way was made to be the middle ground i guess. I made it to be functional, look nicer than the “wrench” way, but still way cheaper than the “expensive” way. I took a little from the cheap way and made it my own to look better. Note: I did all of this with hand tools and a lot of patience. Just thought I’d put this out there for everyone as another idea on how to do this.
So.... here we go....
WHAT YOU NEED:
-Your clutch worm gear out of the cover
-M8x1.25 x 100mm threaded rod (was in stock at my local Menards)
-M8x1.25 threaded coupling nut (also at Menards)
-Old rear brake drum splined shaft and lever (you can buy them for like $20 each online)
-M8 washer
-M8x1.25 lock nut
-M8x1.25 acorn nut
-Metal drill bits in various sizes from 1/16” to 5/8”
-Needle files
-The acceptance that you might fuck this up and have to buy a new worm gear.
(Buy extra hardware in the sizes I mention just in case you mess something up.)
The reason your using M8 hardware is because the threads inside the worm gear for the adjustment screw is M8x1.25. This allows you to not have to drill out the threads in the worm gear like the “wrench” method if you don't want to. But in all honesty, it is easier to drill out the threads because when you weld the coupling to the worm gear it’s difficult to keep the threaded rod (your new adjustment screw) from binding because the weld shrinkage tends to misalign the coupling threads from the inner worm gear threads. But not drilling the worm gear out gives you options if you can make it work. It's up to you.
So the first thing you want to do is get your splined shaft from the rear brake drum assembly. Should look like this out of the drum:
What you’re going to do is drill into the spine end of this right in the center. Use a punch to mark the center and start drilling with small drill bits and gradually you’ll run a 5/16” bit into the end and then you’re done. Drill into the end carefully to a depth that goes past the splines about 1/4” (about an inch or so total depth). Make sure you are drilling in the center because when you drill with the 5/16” bit it’s gets pretty close to the outside and you don’t want to drill a hole through the side of the splines. I did this with a cordless drill by hand so it can be done.
Now cut off the splined end that you drilled about 1/4” or so past the splines. Make sure you cut it off square or, if you didn't, clean it up with a grinder when your done. The 1/4” leaves enough material to weld so you don’t end up welding over the splines. Bevel the cut edge a little too to give your weld a place to sit when you start welding.
Now lay all your pieces and hardware out. It should look something like this:
So first, screw in your M8 threaded rod into the worm gear and turn it until you feel resistance from the ball bearing on the other side. This will help stabilize the rod and help to keep the threads aligned when you weld the M8 coupling nut to the worm gear. If you would rather drill out the worm gear so you don’t have thread alignment issues, use a 5/16” drill bit and carefully drill into the worm gear to remove the threads. Make sure you don't drill into the ball bearing and make sure to clean the shavings out. Be careful not to lose the ball bearing because it can fall out now that the threads aren’t there.
Once you’ve sorted out which method you want to use, insert the ball bearing and threaded rod and then thread on your M8 coupling nut onto the rod until it’s against the worm gear. I beveled the ends of the coupling nut on both sides but you might not need to depending on your welding skills. Once you have it centered and where you want it, weld it in placed taking care not to ruin the threads on the outside of the worm gear. If you do distort the threads, you can make them right again with the needle files and a little time.
As far as the expensive way, it looks great and I have no doubt that it’s probably the most “bulletproof” way to go. My hang up was paying someone $200 for something I felt I could do without a machine shop. As for the “wrench” way, I’m sure it works fine but I just didn’t like the idea of a wrench just hanging off of a bike that I put a lot of time and effort into to make look nice.
So my way was made to be the middle ground i guess. I made it to be functional, look nicer than the “wrench” way, but still way cheaper than the “expensive” way. I took a little from the cheap way and made it my own to look better. Note: I did all of this with hand tools and a lot of patience. Just thought I’d put this out there for everyone as another idea on how to do this.
So.... here we go....
WHAT YOU NEED:
-Your clutch worm gear out of the cover
-M8x1.25 x 100mm threaded rod (was in stock at my local Menards)
-M8x1.25 threaded coupling nut (also at Menards)
-Old rear brake drum splined shaft and lever (you can buy them for like $20 each online)
-M8 washer
-M8x1.25 lock nut
-M8x1.25 acorn nut
-Metal drill bits in various sizes from 1/16” to 5/8”
-Needle files
-The acceptance that you might fuck this up and have to buy a new worm gear.
(Buy extra hardware in the sizes I mention just in case you mess something up.)
The reason your using M8 hardware is because the threads inside the worm gear for the adjustment screw is M8x1.25. This allows you to not have to drill out the threads in the worm gear like the “wrench” method if you don't want to. But in all honesty, it is easier to drill out the threads because when you weld the coupling to the worm gear it’s difficult to keep the threaded rod (your new adjustment screw) from binding because the weld shrinkage tends to misalign the coupling threads from the inner worm gear threads. But not drilling the worm gear out gives you options if you can make it work. It's up to you.
So the first thing you want to do is get your splined shaft from the rear brake drum assembly. Should look like this out of the drum:
What you’re going to do is drill into the spine end of this right in the center. Use a punch to mark the center and start drilling with small drill bits and gradually you’ll run a 5/16” bit into the end and then you’re done. Drill into the end carefully to a depth that goes past the splines about 1/4” (about an inch or so total depth). Make sure you are drilling in the center because when you drill with the 5/16” bit it’s gets pretty close to the outside and you don’t want to drill a hole through the side of the splines. I did this with a cordless drill by hand so it can be done.
Now cut off the splined end that you drilled about 1/4” or so past the splines. Make sure you cut it off square or, if you didn't, clean it up with a grinder when your done. The 1/4” leaves enough material to weld so you don’t end up welding over the splines. Bevel the cut edge a little too to give your weld a place to sit when you start welding.
Now lay all your pieces and hardware out. It should look something like this:
So first, screw in your M8 threaded rod into the worm gear and turn it until you feel resistance from the ball bearing on the other side. This will help stabilize the rod and help to keep the threads aligned when you weld the M8 coupling nut to the worm gear. If you would rather drill out the worm gear so you don’t have thread alignment issues, use a 5/16” drill bit and carefully drill into the worm gear to remove the threads. Make sure you don't drill into the ball bearing and make sure to clean the shavings out. Be careful not to lose the ball bearing because it can fall out now that the threads aren’t there.
Once you’ve sorted out which method you want to use, insert the ball bearing and threaded rod and then thread on your M8 coupling nut onto the rod until it’s against the worm gear. I beveled the ends of the coupling nut on both sides but you might not need to depending on your welding skills. Once you have it centered and where you want it, weld it in placed taking care not to ruin the threads on the outside of the worm gear. If you do distort the threads, you can make them right again with the needle files and a little time.
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