Ultra Bee YZ250 Master Cylinder Install Guide | FactoryZ
Tools Needed:
- FactoryZ YZ250 master cylinder hardware kit (adapter bracket, M8 bolt, 2x M8 washers, M8 nut, short M6 bolt, long M6 bolt)
- Drill
- 3/16 drill bit
- 9/64 drill bit
- 15/64 drill bit
- 5/16 drill bit
- Vise
- 12 mm wrench
- 6 mm Allen key
- Pliers (for bending the cotter pin)
Read This Before Starting Your Install:
This guide walks you through bolting a YZ250 master cylinder onto a Surron Ultra Bee foot brake using the FactoryZ hardware kit. It's for anyone who already has the Ultra Bee foot brake installed and wants to finish the build with a proper YZ250 master, or who's upgrading from another setup.
The install is mostly mechanical: bolt the master to the foot brake bracket using the included adapter, set your lever angle to taste, make sure the pushrod is perfectly aligned with the master cylinder bore, then drill the mounting hole for the M8 through-bolt. The alignment step is the one you can't afford to rush. If the pushrod goes into the piston at an angle, it will chew the master cylinder wall and start leaking fluid.
When you're done, you'll have a solid YZ250 foot brake master bolted to your Ultra Bee, with the lever sitting where you want it relative to the peg. After this install you still need to bleed the brakes before riding.
The hardware kit includes the adapter bracket, an M8 bolt, two M8 washers, one M8 nut, a short M6 bolt, and a longer M6 bolt. You supply the drill, bits, and basic hand tools.
Install Steps:
-
01
Lay out the hardware kit
Start with a clean Ultra Bee foot brake. You should see the two stock holes on the bottom and one on the top. Open the FactoryZ hardware kit and confirm you have the adapter bracket, an M8 bolt, two M8 washers, one M8 nut, a short M6 bolt, and a longer M6 bolt.
-
02
Attach the adapter to the master cylinder
Take the short M6 bolt and run it through the adapter bracket into the master cylinder. Leave it loose enough that the bracket can still dangle and pivot. You'll snug it down after alignment.
-
03
Mount the master to the top hole of the foot brake
Take the longer M6 bolt, run it through the adapter bracket, and thread it lightly into the top stock hole on the Ultra Bee foot brake. Keep it loose for now so you can adjust angle.
-
04
Set your lever angle
Thread the master cylinder pushrod as far down into the lever fitting as it will go without the threads hitting the lever itself. That's the starting point. Lever angle relative to the peg is user preference. The transcript's preference is almost flush with the peg, maybe slightly down, not up. Adjust to what you like.
-
05
Check pushrod alignment with the master cylinder bore
This is the most critical part of the install. The pushrod has to enter the master cylinder piston perfectly straight. If it enters at an angle, it will scrape the bore wall and blow the seal, and the master will start leaking. Sight down the pushrod and slowly pump the lever. It should track straight in and out with no side-to-side movement.
-
06
Check clearance on the back side of the foot brake
Flip to the back side and look at where the master cylinder body bulges. That bulge cannot contact the foot brake, or the master won't sit aligned. The two M8 washers take up that gap on the back side during final assembly. Confirm you have air gap between the master body and the foot brake before drilling.
-
07
Tighten the two M6 bolts once alignment is good
With the pushrod tracking perfectly straight into the bore, tighten the short M6 (master to adapter) and the longer M6 (adapter to foot brake) down all the way. You want the assembly locked in its aligned position before you mark the drill hole.
-
08
Mark the M8 hole location
With the foot brake sitting flat (most of it hanging off the edge of the table so the bracket sits flat on the surface), take a 3/16 drill bit and spin it by hand a couple of turns through the master cylinder's M8 mounting hole into the foot brake. You're just scoring a mark, not drilling through. This keeps the bit from wandering when you move to the vise. Important: leave at least 2 mm of material between the hole and the edge of the foot brake. Bias your mark slightly inboard if it looks tight.
-
09
Pop the master off and move to the vise
Remove the master cylinder so you can clamp the foot brake in a vise for proper drilling. Don't drill it freehand.
-
10
Drill a pilot hole
Start with a 9/64 drill bit and drill a pilot hole straight through at your mark.
-
11
Step up the hole size
Step up with a 15/64 bit, then finish with a 5/16 bit for the final size. The 5/16 hole fits the M8 bolt from the kit.
-
12
Bolt the master on with the M8 hardware
Keep the two M6 bolts just slightly loose for this step. From the back side, set both M8 washers over the hole. Slide the master cylinder on from the front and push the M8 bolt through the master, the foot brake, and both washers.
-
13
Tighten the M8 nut
On the back side, thread the M8 nut onto the bolt. Use a 12 mm wrench on the nut and a 6 mm Allen key on the bolt head. Snug it up.
-
14
Install the clevis pin and cotter pin
On the front, push the pin through the lever and the master cylinder clevis. Slide the cotter pin through the hole in the pin and bend the legs around so it can't back out.
-
15
Final alignment and torque down
Before fully tightening everything, get the pushrod perfectly aligned one more time. With the two M6 bolts snug but not tight, pump the lever gently. The pushrod will self-center as it travels. Once it's tracking straight, tighten the two M6 bolts first, then tighten the M8 bolt last.
-
16
Tighten the pushrod jam nut
Don't forget to tighten the jam nut on the pushrod so your lever angle setting doesn't back off over time.
-
17
Bleed the brakes
The install isn't done until the system is bled. Bleed the Ultra Bee brakes before riding.
Common Mistakes:
-
Tightening everything down before confirming pushrod alignment.
Keep the two M6 bolts snug but not tight until you've pumped the lever and confirmed the pushrod enters the master bore perfectly straight. Tighten the M6s first, then the M8 last.
-
Drilling the M8 hole too close to the edge of the foot brake.
Leave at least 2 mm of material between the hole and the edge. Mark the hole position with the 3/16 bit by hand first, check it, then move to the vise and step up through 9/64, 15/64, and 5/16.
-
Ignoring the bulge on the back of the master cylinder.
Before drilling, check the back side. The master's bulge cannot touch the foot brake. The two M8 washers on the bolt space it correctly during final assembly. If the bulge is contacting, the master can't align.
-
Drilling freehand or while holding the foot brake.
Clamp the foot brake in a vise for the pilot and step-up drilling. Only the initial surface mark with the 3/16 bit is done by hand, and only to score the location so the bit doesn't wander.
-
Forgetting the jam nut on the pushrod.
After final alignment and torque, tighten the jam nut on the pushrod so your lever angle setting doesn't back off under use.
FAQs
What's the most important part of this install?
Pushrod alignment. The threaded rod from the lever has to enter the master cylinder piston perfectly straight. If it goes in at an angle, it scrapes the bore wall and the master will blow and leak fluid. Sight down the rod and pump the lever slowly to confirm it tracks straight before you tighten anything down.
How do I set the lever angle?
Thread the pushrod as far down into the lever fitting as it will go without the threads contacting the lever. From there, lever angle is user preference. Most riders set the lever almost flush with the peg, or slightly below. Some prefer it higher. Run what feels right to you.
What size is the final drill hole?
5/16. Step up to it with a 9/64 pilot, then 15/64, then 5/16. That gives a clean hole for the M8 bolt from the hardware kit.
How much edge material should I leave when drilling?
At least 2 mm between the hole and the edge of the foot brake. Paper-thin will still work, but it's not ideal. Bias your mark slightly inboard if it looks tight.
Why two washers on the M8 bolt?
The back of the master cylinder bulges where it meets the foot brake. The two M8 washers space the master off the foot brake so the bulge doesn't contact it. If it contacts, the master won't sit aligned.
Do I need to bleed the brakes after this install?
Yes. Bleed the Ultra Bee brakes before riding. FactoryZ has a separate video covering the bleed procedure.