I have this in a build thread but I thought I would make a separate post so people can find it easier. This is not a bolt on modification but it works great and only the bearing housing has to be modified so everything else is an easily sourced replaceable part.
Parts needed:
83-84 ATC250r rear brake hub
83-84 ATC250r Rear brake disc
07-09 crf 150r front brake caliper with caliper mounting bracket
07-09 crf 150r front brake pads
Piece of pipe (same I.D. as 185s axle will update size later)
Sheet of 1/8" plate steel (dust shield and lower caliper mounting)
2 Bolts that fit 150r caliper bracket
Brake line long enough to either reach foot brake pedal or handle bar depending on which position you prefer
Optional Parts:
KX 65 or 85 rear brake master cylinder for foot brake
3/16 or 1/4 Plate steel for master cylinder mount
Left Hand Brake Master Cylinder if not using foot master cylinder
Spacers or washers to correctly space the foot master cylinder over the brake pedal
First thing I did was remove the stock 185s brake drum, drum cover, and shoes. Next you will need to remove the brake shoe camshaft, it just slides out of the bearing housing. You will also have to cut the stud that holds the other end of the brake shoes of flush with the bearing housing.
Next a section of the flange that encloses the oem drum and shoes will need to be cut out for the caliper to have room to sit. I don't really have any other way to say what needs to be cut out other than just showing photos. I also cut off the mount that held the oem brake cable. You will need to start the upper end of the section just below the the hole that is already there to mount the oem dust cover to. It will become the upper caliper mounting location. Stop the other end of the section just above the next hole in the flange as it will become the hole the sheet of plate steel mounts to.
Once that cut has been made the sheet of steel will need to be cut out in the shape of a half circle. You can use the bearing housing flange as a guide to cut it as it will mount directly to the lower portion of it like the picture below.
Drill out the upper hole in the bearing flange to accept the bolt that will used to mount the caliper bracket to the flange.
The 250r disc hub has the same spline count as the 185s axle so it slides on the axle just like the stock drum did. Put the disc on the axle and mount the caliper to the bearing flange using the upper mounting position. once this is done you will be able to determine the correct positioning for the lower mounting hole. I rotated the caliper until I had the correct caliper to disc clearance and I had the max amount of pad to disc engagement. I did have to gring the caliper mount a little in order to clear the disc hub when spinning like the picture below shows.
Once the caliper is positioned correctly you can mark the hole for the lower caliper mounting position and drill it out. The more flange you cut out in the above mentioned step the more access you will have to install this lower mounting bolt because its a tight fit to get the bolt started.
After the caliper is mounted with the disc installed take the pipe and cut it to length needed. this piece of pipe allows the axle nuts to have something to push against since the 250r disc hub is not as long as the 185s drum hub. It will look like the picture below.
If you are going to run a handlebar mounted brake master you can just run the brake line from the caliper to the master cylinder and you are done. If you want to run a foot master more fabrication and welding is involved and you can continue reading below.
First thing I did was cut the cable attachment arm off the oem brake pedal. It will be welded back on in a different position so save as much of it as you can. I used a 1/4 inch piece of plate steel and drilled and tapped it to accept the foot master. I used the washers to space the master far enough off the mount so it did not interfere with the frame tube but still sat over the center of the brake pedal. Once its mounted to the steel you can locate the correct positioning to weld the bracket to the frame and the correct position to weld the arm back on the foot pedal as well. It will look something like the picture below. once both of the are welded you can attach the brake line to the master. You will need to find a place to mount the external brake fluid reservoir I can say to use my location because its no longer a stock frame in that location due to the rear suspension conversion.
This isn't the best step by step tutorial but I figured it could help give somebody, with the skills, some ideas on how to make it work. And I totally know it can be done much nicer I just don't have the time or patience. I just wanted a bike that performed great and I could beat on without worrying about messing up the cosmetics and that is what I got. this brake setup will lock the back tires up on asphalt without question. It stops the bike great and I don't feel it needs anymore performance out of the setup at all
Here are some photos of after I had it all buttoned up and all the frame parts painted. Still need to finish making the rest of the bike pretty.
Happy to answer any questions or concerns
My original build thread is located here
http://www.3wheelerworld.com/showthr...n)-2021-Update
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