How To Bleed Ultra Bee Brakes
A Surron Ultra Bee master cylinder has a tiny bore, so one stroke moves only a few drops of fluid. If the piston does not fully return and pull fresh fluid from the reservoir, you push the same pocket of air down the line and suck it right back up. Pump it a thousand times and nothing changes. Here is the cycle that actually clears it.
00 Know Your Setup
A stock Ultra Bee runs two hand levers: front on the right, rear on the left. Anything else is a conversion. Each master cylinder and the line it feeds is a separate circuit, and you bleed one circuit at a time.
Stock
Two hand levers, one caliper each. Bleed the front and rear independently.
Foot Brake Swap
Pedal master replaces the rear hand lever. One circuit, bench bleed the master first.
Hand And Foot
Two masters. On a dual caliper bracket, bleed each side on its own. On a shared caliper, bleed each master through the same bleeder, one at a time.
01 Before You Start
Fluid
- Match the DOT rating printed on your reservoir cap. Ultra Bee and most aftermarket masters run DOT 4 or DOT 5.1.
- Use a fresh sealed bottle. Open fluid pulls moisture out of the air and boils sooner.
- Never add DOT 5 silicone fluid. It does not mix with DOT 3, 4 or 5.1 and will ruin the system.
Tools And Prep
- Box wrench that fits the bleeder. Skip the crescent, it rounds the flats.
- Clear hose and a catch bottle with fluid in the bottom.
- Syringe for reverse bleeding, new crush washers, rags, water.
- Bike on a stand with the wheel off the ground.
- Brake fluid strips paint and attacks plastic. Cover the shrouds and flush spills with water.
02 Set The Master Up First
Most failed bleeds are lost here, before a drop of fluid moves.
Level It
Rotate the hand master on the bar until the reservoir sits flat. A tilted reservoir traps air in the high corner and can uncover the port.
Bench Bleed It
A new foot brake master goes in dry. Fill it and work the pushrod by hand until fluid moves cleanly, before the line goes on.
Set Free Play
The lever or pedal must rest with slack. Any preload holds the return port covered and the bore never refills.
03 The Cycle That Actually Works
| Step | Do This | Why It Matters |
|---|---|---|
| 01 Open | Crack the bleeder 3/4 turn | Gives trapped air a one way exit |
| 02 Push | Press the pedal down slow, or pull the lever in slowTake three full seconds. Fast strokes churn the fluid into foam. | Foam will not bleed out, it just recirculates |
| 03 Close | Shut the bleeder while the pedal or lever is still held down | Nothing gets pulled back in |
| 04 Release | Let the pedal or lever return slow, then restAbout three seconds back to the stop. | Bore refills with fresh fluid from the reservoir |
| 05 Pause | Wait two seconds, then repeat | Air floats up to the bleeder instead of staying suspended |
Run the cycle until the hose comes out clear with no bubbles, then close the bleeder for good and torque it. Top the reservoir every four or five cycles. If it runs dry you start over.
04 If It Still Will Not Bleed
Reverse Bleed
Push fluid up from the caliper with a syringe. Air wants to rise, so let it. This clears most stubborn lines in one pass.
Free Play
Check the slack again. Cable adjusters, pedal height and lever reach all creep and quietly preload the master.
Nipple Up
Unbolt the caliper and tilt it so the bleeder is the highest point. Tap the body. Support it, never hang it by the line.
Torque Banjos
Loose crush washers suck air on the return stroke and give you phantom bubbles forever. Fit new washers and torque them.
Still spongy with a clear hose? Air is sitting somewhere above the caliper. Crack the banjo at the master, at the tee on a shared caliper setup, or at any high point in the routing, and let it weep while a helper holds pressure.
05 Check Before You Ride
- Lever or pedal comes up firm and stays firm when you hold it.
- Bleeder closed and dry. Banjo bolts torqued with no weeping.
- Reservoir filled to the line, diaphragm and cap seated.
- Pump the brake until the pads contact the rotor before you move the bike.
- Test at walking pace first, then build speed.
Do Not Ride It
If the lever pulls to the bar or the pedal sinks under steady pressure, the system still has air or a leak. Bleed it again. Brakes are the one part of the bike with no margin for a maybe.