The Butler Mod

Rear Brake Proportioning Valve

Many of us who ride the Yamaha Venture and the Yamaha Royal Star Tour Deluxe have always felt that the rear brakes on these bikes is way to sensitive.  It takes very little pressure on the brake pedal before you find yourself with the rear tire locked up.  This is pretty easy to control in normal day to day driving and controlled stops but in a panic situation with adrenalin coursing through your veins, it can be an entirely different scenario.  This is a problem that Rick Butler has been working on for a few years and after looking into linking the front and rear brakes as Yamaha did on the first gen Venture and various other options, he finally came up with simple and very cost effective solution to the issue.  An adjustable proportioning valve in the rear brake circuit works very well.

What does a proportioning valve do?  Simply put, it controls the amount of pressure that gets to your brake caliper.  An adjustable proportioning valve allows you to set that pressure to your personal preference.  Then when that adrenalin is flowing and you STOMP that rear brake pedal, the proportioning valve ensures that the massive pressure you just sent to the brake gets tamed down a bit before the tire locks up and sends you into an uncontrollable skid.  

This is not new technology.  Custom car builders, especially hot rodders, have  been doing this for years.  One of the first things the custom builders often do is convert the old rear drum brake systems to disc brakes.  While drastically improving breaking, they also end up with this same problem of the rear brakes locking up much to quickly.  They correct this problem in the exact same manner that Rick is applying to our bikes.  If you do a search on the Internet for "Proportioning Valves", you will find a number of write-ups on this exact topic.  We are lucky that Rick has already done the research for us, found a compact valve with a straight through design that works great on our bikes and spent about a year with it on his bike doing the testing for us.  Due to his work, it is now very easy for the rest of us.

The installation of this system is very simple.  If I were rating it on a 1-5 ranking system, I would give it a 1 if you get the parts from Rick and maybe a 2 if you order things and do it all yourself.  The reason for that is only because the outlet side of the valve has to be re-threaded to our metric needs and that will add just a bit of difficulty if you decide to order your components and do it all yourself.  I recommend that you go through Rick as he is making very little, less than he should be and does a great job.

So, here is the very simple install procedure.  I am a bit embarrassed posting pictures of my bike as it is FILTHY.  This was done right after my close to 5,000 mile journey to Fort Collins, CO and the bike still has dirt and grime attached from several states.  Oh well.  Maybe I'll wash it one of these days.

You do not need a lift or centerstand to do this job.  Simply remove the left saddlebag so that you can get to the rear brake caliper and you are ready to go.

The first thing you need to do is to remove the rear brake line.  Just remove the bolt at the rear caliper, a couple of retaining clips on the line, and unscrew the line at the master cylinder.  I had previously installed a stainless steel line so yours will look a little different but the procedure is the same.

Removing line from rear caliper

Removing line from master cylinder

Once the old line is removed and out of the way, it is time to screw the new proportioning valve onto the master cylinder.  In order to get the clearance needed to screw it on, you need to remove the mounting bolts for the master cylinder and rear brake pedal assembly.  This consists of three bolts that go through the bottom of the floor board mounts and into the brake assembly.  Simply remove the three bolts and then you can tilt the master cylinder down and screw in the proportioning valve.

Look carefully at this picture and you can see the holes where I removed the bolts.  Three bolts through bottom of the floorboard mounts.

Remove the old fitting that screws into the master cylinder. 

Screw the proportioning valve into the master cylinder.

Route your new SS line and connect on both ends.

Replace metal cover over line at master cylinder end.  Now Rick told me that I might have to trim the cover for it to fit but I did not have to do that.  I bolted right on.

Now that is all there is to the installation.  Now it's just a matter of bleeding your brakes and then setting the proportioning valve to your liking.  In order to more easily bleed your brake, you will want to open the proportioning valve at least a couple of turns or even all the way, but just make sure that it's not closed down.  Once your brakes are bled, you can then take it for a test ride and get it setup the way you want it.  This valve is easily adjustable and has colored rings to show what number you are at.  Rick is running is at two turns out and that is where I started also.  As I ride it more, I will adjust it if necessary to my own preferences. 

One further note.  The adjustment knob on this thing is pretty easy to turn.  Rick drills a hole through the cap and body so that once you get the valve set to your preference, you can put a piece of wire through it to ensure that it stays where you want it.  I highly recommend that you do that also.