ABS Modulator Service
Tourer
Joined: Jan 2018
Posts: 319
Likes: 139
From: Seattle
As mentioned, metallurgy whether Chinese or German doesn't matter. And I familiar with Chinese metal or as I call it Chetal. The metal valves in the HCU are surrounded with o-rings. It's the o-rings and moisture ladened crystallized Dot4 that cause the issue. Those crystals (or some refer to as sludge) that develop behind the valves is disrupted and allowed to escape forward of the valve when the solenoid is energized thus moving the valve forward into the bypass position. Then the crystals/sludge become lodged between the o-ring and port thus prohibiting the valve from returning to it's normal position. Once the pump shuts down the end result is the master cylinder being cutoff from the caliper.
Last edited by FPV; Apr 12, 2018 at 06:29 PM.
Advanced
Joined: Mar 2016
Posts: 81
Likes: 22
From: Orange, CA
As mentioned, metallurgy whether Chinese or German doesn't matter. And I familiar with Chinese metal or as I call it Chetal. The metal valves in the HCU are surrounded with o-rings. It's the o-rings and moisture ladened crystallized Dot4 that cause the issue. Those crystals (or some refer to as sludge) that develop behind the valves is disrupted and allowed to escape forward of the valve when the solenoid is energized thus moving the valve forward into the bypass position. Then the crystals/sludge become lodged between the o-ring and port thus prohibiting the valve from returning to it's normal position. Once the pump shuts down the end result is the master cylinder being cutoff from the caliper.
Seasoned HDF Member
Joined: Jun 2012
Posts: 14,438
Likes: 2,421
From: Pittsburgh, Pa
As mentioned, metallurgy whether Chinese or German doesn't matter. And I familiar with Chinese metal or as I call it Chetal. The metal valves in the HCU are surrounded with o-rings. It's the o-rings and moisture ladened crystallized Dot4 that cause the issue. Those crystals (or some refer to as sludge) that develop behind the valves is disrupted and allowed to escape forward of the valve when the solenoid is energized thus moving the valve forward into the bypass position. Then the crystals/sludge become lodged between the o-ring and port thus prohibiting the valve from returning to it's normal position. Once the pump shuts down the end result is the master cylinder being cutoff from the caliper.
Tourer
Joined: Jan 2018
Posts: 319
Likes: 139
From: Seattle
I wouldn't go so far as to say that. The unit #48343-09 is assembled in a way as to render it non-serviceable. Even though the valves can be removed from the inside once the pump motor is removed those valves were originally installed from the outside of the housing then capped and the pump motor is a light press fit. Take a look at the second video by John Maxwell in post #10 of this thread. Start at around 6 minutes into the video. You'll get an idea of how taking the HCU apart essentially destroys it.
The key to avoiding failure is to never let the brake fluid reach an excess of 4% moisture. If that has occurred before the current owner purchased the bike then odds are not in favor of the unit lasting no matter what level of maintenance is performed.
The key to avoiding failure is to never let the brake fluid reach an excess of 4% moisture. If that has occurred before the current owner purchased the bike then odds are not in favor of the unit lasting no matter what level of maintenance is performed.
Advanced
Joined: Sep 2017
Posts: 71
Likes: 7
From: Wisconsin
It seems to me that the videos show that you can not disassemble the unit with standard hand tools and the tech says that the hcu is not serviceable.
HDF Community Team
Joined: Nov 2012
Posts: 6,186
Likes: 2,412
From: USA
Perhaps. But there is nothing to lose by trying on a failed unit. Personally, I've taken apart and repaired many non-serviceable items.
Seasoned HDF Member
Joined: Apr 2015
Posts: 10,001
Likes: 5,266
For most non-serviceable components, you can't repair them because the manufacturer doesn't sell parts. The best you can do is refurbish the failed parts, which I wouldn't chance doing on a critical component such as an HCU.
Tourer
Joined: Jan 2018
Posts: 319
Likes: 139
From: Seattle
Words of wisdom!
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
HDF Community Team
Joined: Nov 2012
Posts: 6,186
Likes: 2,412
From: USA
Harley says the shocks are sealed and non-serviceable and won't sell any parts for them. Showa sells parts to rebuild the shocks though, and even provides some tuning information. Just an example of going around the obstacles and getting it done.
if one opened up the HCU and found rusted/pitted metal, that likely would be the end, unless replacement parts were found or made. But, if it's merely sludge buildup, a simple cleaning would get them moving and working again.
If I had a failed HCU, I'd find it worthwhile to explore it and see if I could fix it. But that's just me.