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BBSHD on a Sun EZ-3 USX-HD

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    BBSHD on a Sun EZ-3 USX-HD

    Where to start… As a first-time builder, I spent a great deal of reading from the forum. Thanks to the admins and the seemingly endless knowledge shared by e-bike community.

    My build is not “totally custom” but it had a few challenges that are not likely encountered by most. I am adding motive power to a Sun EZ-3 USX HD trike.

    I began with the battery. I purchased the 24Ah 52V pack. I was looking for a battery with high output and huge capacity. This met the need. The battery pack is well built with good quality connectors and very flexible cables. The included triangle bag is nicely constructed. It is a little large… For a frame mount, the extra space may improve their utility. (easier mounting, extra storage?) Because I am not mounting within the confines of a frame, I had to devise a means of filling the space with something that will protect the battery. I recovered some EPE foam from a packaged I had received. The EPE is a dense closed cell foam that provides good shock absorption and memory retention (springs back to the original shape)

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    I cut the EPE to fill the extra space. Because of the mounting location, I needed more protection on one side. The mounting location will be under the back of the seat, above the frame. The pack is suspended from the seat frame. The bottom of the pack (with the thick pad) rests on the top of the frame tube.
    Click image for larger version  Name:	battery mounted.jpg Views:	1 Size:	190.1 KB ID:	40493

    With the battery located, I turned to dis-mounting the bottom bracket to mount the BBSHD. The first challenge I had to overcome was the steering linkage. As an under seat steering trike, the steering linkage runs under the bottom bracket, from the middle of the bike to the front fork. The current configuration interferes with the mid-drive. I tried to relocate the linkage but there was no way around the BBSHD. I had to fabricate a new steering linkage.

    I began the new linkage with a length of 3/4 “ EMT conduit as it was a piece of surplus material from another project. I machined a pair of plugs to weld into the ends of the tube and tapped them to accept the heim joints from the previous linkage. After a few bends and tweaks I came to a shape that cleared the mid-drive and tucked in behind the crank arm. It wasn’t pretty but it was functional. As I progressed further into the build, I became less and less happy with the results of my handiwork. I picked up a length of ½” EMT and machined a new set of plugs to weld in. The new linkage (shown below) was much more elegant and fitting of this build. I guess the first one was an opportunity to practice my tube bending.
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    The initial mounting of the mid-drive was straight forward, with no interference. The location of the motor is similar to most 2-wheeled bikes, under the down tube. I was fortunate to learn the BBSHD fits through the bottom bracket without modification to the frame or BBSHD.

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    Now I can begin to lay out the cable routing and management. I quickly learned the main cable assembly, once connected to the BBSHD, was long enough to reach my handle bars, but not much more. The brake sensor wires in combination with the magnetic switches were long enough to mount without modification. They were the only ones… I chose to lengthen the cable rather than add extensions for reliability. (fewer connectors, fewer connections, fewer opportunities for corrosion, easier to troubleshoot – In my opinion…)

    My background in cable assembly provided a useful set of skills. The wiring diagrams I found on the Forums was a huge help. (Thank you to Sebs for the detailed diagrams) It provided the correct color coding and connector pin-out for confirming the work I was about to do. I began with the speed sensor, as it was an easy choice. I mounted the sensor and measured the amount of additional cable needed. I created a short cable to add to the middle of the cable coming off the sensor. I used a cordless drill to twist the wires together to achieve about 3 turns per inch (easier to manage a small group than 3 strays)
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    With a little planning and a LOT of shrink tubing, I was ready to install the main harness.

    The handlebars for the under seat steering do not provide any reasonable mounting locations for the dash panel or user switches. Time to fabricate a mounting location. I mocked up a sample with some plastic tubing to get an idea where to bend the tubing and a starting point for the length. I worked with 1/2" EMT conduit for the tubing. (inexpensive, plentiful, easy to form, inexpensive) To attach the mount arm to the handlebar, I purchased an 8” handlebar extension that came with 2 mounting clamps. (donor parts) The conduit tubing was a little smaller than the original tube the clamps were intended for so I made an additional rubber shim to ensure a secure mount. I gave the conduit a few bends, did a few test fittings, a few more bends, more test fitting and finally arrived at the form in the pictures. They position the dash panel forward and above the right hand controls. I was able to position the throttle and selector switch within easy reach as well.

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    The gear sensor was also added to make shifting a little easier. The only reasonable location to mount the sensor was on the rear of the frame, near the derailleur. Because of the proximity of an adjacent cable, I had to mount the gear sensor on its edge to make it fit. Click image for larger version  Name:	gear sensor 2.jpg Views:	1 Size:	149.5 KB ID:	40500

    So… Battery mounted, Mid drive mounted, controls mounted, time for the chain ring. I started with the Lekkie 42T Bling Ring on the front because it was the same size as the middle ring of my former triple set. It also looks really cool. I added the provided cranks my Shimano PD-530M pedals.

    Click image for larger version  Name:	BB after 2.jpg Views:	1 Size:	170.9 KB ID:	40501(This is an image of the first version of the steering linkage also - It was ugly!)

    Time to test the result… I powered up the unit and watched the display come to life. Slowly I began to rotate the cranks and the BBSHD kicked in. I ran it up and down through the gears, watching and listening. Everything was running pretty smooth and quiet.

    I took the trike down from the stands and powered up the display again. The system made no noise or attempt to move. I wasn’t quiet sure what to expect… I mounted the pedals and began to rotate them when the BBSHD engaged. It was set on PAS 1 so it pulled gently, applying less than 200 watts, but providing a noticeable amount of effort. As the grin on my face began to grow, I tapped the “+” button to go to PAS 2 and headed down the driveway. This thing was amazing! I pedaled the length of my driveway for a few laps to listen to the bike and listen for new sounds. It all seemed good so off to the street. I rode the length of my street, shifting gears and listening for anything out of the ordinary. All was good.

    By now I was really excited, I turned around and grabbed a handful of throttle. The bike quickly accelerated and down the street. 15… 20… 25… still pulling hard and I’m running out of space. I made a few more passes and called it a day, satisfied with the results.

    Over the next few weeks I put about 200 miles on the trike. The BBSHD performed flawlessly. After about 100 miles, I pulled the Lekkie Bling Ring and installed the 46T steel ring that came with the kit, to decrease my cadence. I will purchase the 130mm ring adapter to reinstall my former 42T and 52T rings.

    I have made several rides of more than 50 miles, without a concern. (used about 60% of the battery) Hills are no longer intimidating. Now I can ride at any speed I choose, and easily stay with the pack on group rides.

    I am definitely one more satisfied Luna customer.

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    I have now ridden more than 500 miles with the BBSHD in place and no issues with the mid-drive, battery or associated Luna parts. I have broken the chain twice (separated links - May be my fault??) I can cover more than 80 miles on a single charge using the PAS. Spend a lot of time picking bugs out of my teeth because I can't stop grinning!!!!

    Cost Breakdown
    Item Description Cost (USD)
    Trike Sun EZ-3 USX HD (purchased in 2011) $ 1,599
    Motor Bafang BBSHD 1000 Watt Mid-drive kit $ 679
    Battery TRIANGLE 52v Panasonic GA 18650 24ah $ 799
    Display Luna 750c Full Color Display $ 45
    Gear sensor GearSensor for Derailers $ 45
    Programming cable Bafang Programming Cable $ 20
    Brake Sensors Magnetic sensors to use your own brake levers $ 15
    Chain ring Lekkie Bling Ring black, 42T $ 90
    Charger 52V Advanced 300W Ebike Charger $ 80
    Wrench Luna Wrench $ 19
    Chain Shimano HG40 6/7/8-Speed Chain (2X) $ 36
    Cassette Shimano 11-34 Freewheel $ 18
    Tubing 1/2" EMT (local hardware store) $ 4
    Misc. Hardware Nuts, Bolts, zip ties $ 10
    Mounting hardware Handle bar Extension $ 16
    Total $ 3,475
    Description Link
    Sun EZ-3 USX HD (purchased in 2011)
    Bafang BBSHD 1000 Watt Mid-drive kit
    TRIANGLE 52v Panasonic GA 18650 24ah
    Luna 750c Full Color Display
    GearSensor for Derailers
    Bafang Programming Cable
    Magnetic sensors to use your own brake levers
    Lekkie Bling Ring black, 42T
    52V Advanced 300W Ebike Charger
    Luna Wrench
    Shimano HG40 6/7/8-Speed Chain (2X) Local Bike Shop
    Shimano 11-34 Freewheel Local Bike Shop
    1/2" EMT (local hardware store)
    Nuts, Bolts, zip ties
    Handle bar Extension
    Attached Files
    Last edited by 3wheeler; 08-20-2017, 03:45 PM.

    Originally posted by 3wheeler View Post
    I used a cordless drill to twist the wires together to achieve about 3 turns per inch (easier to manage a small group than 3 strays)
    Excellent build and write up. I have never used a cordless drill for twisting wires together. Can you share how exactly you do it?


      Hi Fred,

      Its a pretty handy way to get your wire bundles to a manageable form.

      You will need to add a little extra length to the wires, when measauring for your need. Some length will be consumed in the twisting. Also the more wires in the bundle, the more that will be consumed. For bundles up to about 5 wires (assuming 22 gauge wire) I add about an inch per foot of wire harness. Larger gauge wire will require additional length.

      Open the chuck of your cordless drill. (be sure the drill/driver is set to LOW speed, for your safety)
      Gather your wires together, get them as straight as possible and zip tie one end together. (This end will be put in the drill chuck)
      Place the zip tied bundle in the chuck and tighten the chuck on the bunch. You need to place the zip tie about 2 inches from the end of the wires, then fold them over at the zip tie and stick it in the chuck.
      Stretch the wires out straigh, as best you can, and hold the loose end in your hand.
      Start the drill slowly and hold the wires. They will begin to twist together very nicely.
      As your twist begins to approch the end, you can determine how tight to twist the bundle. Hold the bunch tighter and keep the drill turning if you want a tighter twist.
      Don't go too crazy. You can over twist the bundle and break your wires. (You would have to work pretty hard to do that!)

      I hope that helps.



        Thank you for the write up I have the same bike and hadn't thought of the steering linkage. Ugh I don't weld.

        Would you be willing to make another? If so what would that cost a broke bike enthusiast? The steering link bar I mean.
        Last edited by BigJon; 07-23-2017, 06:31 PM.


          Hi BigJon,

          I don't think I could easily make one that would work for your bike without having the bike in my garage. I had to do a lot of "Finessing" to the linkage as well as the connections on both ends. I had to "fit" the rod to my trike, around the BBSHD and through the space between the crank and frame. I added a 1.25" longer bolt and 1" standoff nut to the front, I had to twist (bend) the rear plate about 15° clockwise to reduce the strain on the heim joint at the rear. (the angle was to much for the joint.)

          In leiu of welding, you could drill and tap the inserts to accept small screws through the tube, into the insert. If you made the insert deep enough, you could drill straight through and use a rivet. Welding is A solution, not the only solution.

          Where there is a will, there is a way!!!


          • BigJon
            BigJon commented
            Editing a comment
            I ended up ordering overhand steering components and intend to remove under seat steering. how is this build working out for you. as i am still waiting on parts to arrive.

          Updated 9/15/17:

          I added a 130 BCD adapter to the BBSHD so I could mount 2 chain rings up front (42/52) In doing this, I found the derailleur was not reaching to the outside ring. I measured the distance it was short and machined a spacer to add in behind the derailleur cage. I cut the cage free and welded the spacer in. (TIG welding is a wonderful thing!!!) With the new spacer added, the derailleur could easily reach the outside ring. I mounted the derailleur back to the bike and made a few adjustments and it worked like a champ! (see the video).

          By adding the 52T ring, I was able to increase my top speed by about 4 mph, I can cruise along comfortably at 18 mph without pedaling wildly.

          I have seen that I consume battery at an increased rate of about 20%. (Wattage has increased about 20-25% at each PAS level.)

          Click image for larger version  Name:	dual rings.jpg Views:	3 Size:	1.71 MB ID:	45261Click image for larger version  Name:	deraileur mod.jpg Views:	6 Size:	221.1 KB ID:	45263
          Attached Files
          Last edited by 3wheeler; 09-15-2017, 07:44 PM.


            Hows the range on it? Given her a long ride yet?


              I have gone on a 67 mile ride (less than 500' of total elevation), with no issues. I probably had about 10 miles left in the battery. I have had to adjust my pedaling cadence to improve the battery usage. I spin the pedals a little faster (about 1 gear lower) to keep the power usage right around 300 watts. This seems to be the magic number for me. I get a pretty good range and do not have to worry about running out of battery. I am able to cruise along about 18 mph and enjoy the ride!


                Nice Write up. I purchased a USX that was hanging in guys barn and had hardly been ridden for $400.00 this year. It actually looks brand new. I bought it for a lady friend who is on a fixed income and wanted it for exercise. She is supposed to pay me for it but has not done it yet and its been a few months. 3 Wheeler you did a good job with this three wheel conversion. Did you ever consider using a front hub so you could still fold the Trike? I wonder if using a front hub would be as expensive to do as the Mid Drive?



                • BigJon
                  BigJon commented
                  Editing a comment
                  Front hub or mid drive wouldnt eliminate the folding along the shock you just need to pull a bolt from the shock and remove steering linkage. Honestly My build is better for folding (I put an adjustable neck on the handlebars for that purpose ( tuning that bar every time is annoying. I did it when I bought the bike a snapped one of the M10 threaded peices on mine)

                Jon I think that is how you are supposed to fold it. You have to pull a bolt and the USS linkage. Its easy to snap some of those M10's. You have to be careful because some of them only like to break loose from one side. If you google the Bicycleman , Peter has the manuals up on his site for the Sun USX if you need to look something up.

                Last edited by ComicDom1; 10-03-2017, 01:30 PM.


                  Wow. What a timely find. I happen to own a Sun EZ-3 Trike essentially identical to the one in this thread. With this coronavirus shelter at home stuff I have time on my hands to do something. I was actually thinking about acquiring an electric bike when I stumbled on this forum and this topic. Must be fate! I'm not as active as I used to be BUT I am highly motivated by the potential conversion of my EZ-3 Trike to electric power. My wife is going to wonder what I'm doing in the basement. I'll surprise her with a result (I hope)... Right now I am searching for a good source for the BBSHD motor kit. And think I've narrowed the options to the 46T sprocket and a 500C display panel. As it happens I have a rather large 48V Lithium-Poly battery pack from a former project I abandoned a couple of years ago. I think I can adapt that battery pack to this motor. Its about 20lbs of battery - not sure what its capacity rating was.

                  If the original poster is still here, maybe he could advise on one thought I had regarding the USS linkage. If I flip it over, - putting the bent portion upside and add roughly 2" stand-offs at each connection point - will that be reasonably close to a working solution? Worst case I'll fabricate something for this - just hoping for a simpler solution.

                  I REALLY, REALLY appreciate the clear thread detailing the build of your Trike. Owning an identical model trike this gives me inspiration that it is indeed possible. And if I can score a deal on a BBSHD soon I'll be on my way to a very similar solution.

                  Now off to my bank account to make sure I can finance this little indulgence! lol


                    Keep me posted on your progress and I will keep you posted on my progress. Good luck.


                      Ordered my BBSHD via Luna Cycles. Opted for the non-street legal version (whatever that means). My battery is a relic from a prior (7 years ago) abandoned project - hopeful it will still hold a charge. Its a huge LifiPO4 battery (12.5 x 9.5 x 6 inches) and weighs probably 25 lbs. Rated at 48V, 30A, 1500W - it should be sufficient. If not I'll be shopping for a battery soon.

                      I _think_ I can make the original under seat steering linkage work by mounting it on the bottom side of the front and back brackets, and probably adding a 1" stand-off on the bottom side of the front bracket. Measures close to 5" clearance to the frame - but I'll learn more as I get into it. The motor spec shows the clearance needed at just under 5 inches.

                      I'm not planning (at this point) to incorporate a front derailleur just to keep things simple. But who knows? Maybe phase 2 of the project? lol

                      Oh - today I even ordered a "USB programming cable" for the Bafang. As a programmer I figure it never hurts to be able to tinker with the innards of things. Oh and I ordered a nice set of wiring connectors for the battery.

                      Just sitting around now waiting for bits and pieces to show up so I can get on with it. If nothing else, I will try this weekend to get the battery mounted (behind the seat), and re-work what is necessary for the seat back support.

                      I'll do pics of things and post as I get underway.


                        Sorry Guys, I have been away for a while but found the messages today!

                        The USX-HD is a great trike! Tough as nails and easy to work on! I put over 6000 miles on mine!!

                        I agree with Hawk521, Luna Cycle has the BBSHD kits at good prices. Good quality Batteries too!! Your 48V batteries should work well enough. The 52V batteries have more PUNCH without damaging the motor or components.

                        I recommend using the Eggrider V2 display. It gives you complete control over the BBSHD programming through a BT connection to your smartphone. No computer needed, no programming cable, no FLAKY software... The app is easy to use and can be programmed on the fly!!

                        I tried to used the original USS linkage as a first option. Getting it to clear the motor AND pedals is the challenge. I found it easier to make a new one with 1/2" EMT and a couple 1" AllThread nuts for spacers. I had to "tweak" the mounting tabs at both ends to get the angle the let the heim joints operate smoothly.

                        There is plenty of clearance for the BBSHD to fit under the Bottom Bracket.

                        I was able to use a 130 BCD adapter and two of the original three chain rings (42/52) for the front, with a modified derailleur, to retain a high and low range. A front derailleur for a fat-tire bike (or derailleur mount) should get you close enough also.

                        I have since sold that trike without all the BBSHD mods. I have the steering linkage and 130 BCD mount (I think...) I may be persuaded to sell them if you are really interested... Contact me.

                        I found that I have the steering linkage, 130 BCD BBSHD adapter, modified front derailleur, accessory mount bar (see picture of display mount above) as well as the super-duty mounting clamps for the accessory bar. All the custom fabled parts to add the BBSHD.
                        Last edited by 3wheeler; 05-06-2020, 05:33 PM.


                          ComicDom1 I did not consider a hub drive as I wanted something with a lot more grunt. The mid- drive gives more toque at lower speeds and is far less prone to over heating issues in sustained use applications. The BBSHD is pretty bullet-proof for the average user. a few mods make if a KILLER mid-drive (change out nylon drive gear, add the Luna Cycle Ludicrous controller) for the super user.

                          The USX-HD CAN be folded with a few tools, but I don't recommend doing this. You will constantly be messing with the steering linkage and suspension mount. Not sure what the manufacturer recommends.

                          Thanks for reading the post!