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    Sur-Ron mechanical troubleshooting, repairs, adjustments, tips & tricks

    Modifications, adjustments, tips & tricks

    Here is the list of the available modifications, tips & trick:
    Last edited by paxtana; 02-16-2024, 01:22 PM.

    Sur-Ron headset

    Luna now offers a high end replacement headset kit from Cane Creek, it comes with a PVC pipe to make the installation a breeze.

    Click here to see the listing

    Click image for larger version  Name:	surron_cane_creek_headset__01916.1537046626  .jpg Views:	1 Size:	64.0 KB ID:	74778

    See below for what makes up the Surron headset. With this info you can service headset, replace components and potentially switch to a different fork if you wanted to.

    The part numbers are for a HOPE headset and will work fine with the Sur-Ron.

    Click image for larger versionName:	head set.pngViews:	1Size:	222.2 KBID:	71588

    For the removal & installation, please watch this video
    Cane Creek

    Sur-ron HD headset,

    Sur-ron headset DIY installation by John Holmes, while he got into some issues, it's good to watch as he explains well the step and what to do if you are in trouble!

    Last edited by Sebz; 03-11-2022, 10:32 AM.


      Tire and tube replacement.

      How to fix a flat?

      This is not a standard mountain bike so you will not be able to use your little plastic levers, you will need real MX style metal tires levers (also called tires spoon).

      Something like this is probably sufficient for the stock tires

      You will also need a MX tube to replace it, The stock one is on the thin side and if weight is not an issue for you you can opt for a heavy-duty thicker tube. The size you will need is a TR-4 70/100-19 good for 2.5" to 2.75". Example: Michelin 32403 Heavy-Duty Inner Tube - 70/100-19 - TR-4

      Change your tire?

      The size is the same as the front and they are 70/100-19 tires. You may try to use a larger tire but you may have to shave some block or dish the wheel a little. There is simply not much space to work with.

      So far we've seen a few members or the Sur-ron Owners group on Facebook that changed the tires to something better and wider, here is the list:

      All of the following tire will fit bigger than the stock ones, even if it'S the same size!!! The stock CST tires are smaller than the usual 70/100-19 down that list.

      MX tires:
      Bridgestone M-403 70/100-19
      Dunlop MX 33 (likely the biggest of the 70/100-19 tires)

      Kenda 760 trackmaster II (great all around rear tire) 70/100-19
      Pirelli Scorpion mx mid soft 32 70/100-19
      Maxxis M7304 Front 70/100-19 Maxxcross
      Michelin Starcross MS3 Soft/Mixed 70/100-19

      Dual purpose tires /Trial tires
      These use a different size standard, instead of using metric (70/100, which means 70mm width and 100 means that height of the tire is 100% of 70mm) The use imperial width, So stock is 2.75" so anything bigger could possibly rub on the chain, some 3.0" and 3.25" do fit
      Shinko SR241 Series Trials Tire 2.75x19 fit very well.
      *Shinko SR241 Series Trials Tire 3.50x19 (will rub so be prepared to align your wheel, remove the kickstand or shave the knobs on the right side)

      Here are a couple comparison pics from BeenRydin on the Sur-Ron owners facebook group which may be useful to reference sizing
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      Last edited by Sebz; 05-11-2021, 09:31 AM.


        RST fork replacement axle and axle nut?

        If your local bike shop can't order you a new axle from the RST distributor you can order them online, they seem to be harder to get in the USA. we found you this place that has them in stock if you are in need.

        Complete axle with the locking nut

        Aftermarket alternative to the first link

        Just the locking nut

        Another option
        Last edited by paxtana; 12-15-2020, 09:42 PM.


          Upgrading/replacing Sur-Ron brake pads and disks

          The Sur-Ron uses 4 piston downhill type hydraulics brakes and 203mm disks.

          The caliper uses Shimano replacement pads, look for a pad for :Saint M810, Saint M820 or ZEE M640.. You can even use aftermarket pads like Kool Stop, you can also change the compound to metallic and such. This is an example of a compatible replacement.

          If you want to upgrade the complete braking system you can too, Shimano Zee or Saints, Magura MT5/MT7 or even Hopes. Just remember that the front brake is the right lever as most MTB brakes are the opposite,

          For the disks, the front uses MTB standard 6 bolt rotors so you can use any disk you like, you can go with a Shimano Icetech rotor or go with a floating rotor too. IF you plan on going over 203mm you will need a new caliper mount. But the rear has a different bolt pattern and standard mountain bike disk will not fit. You will need to use rear Sur-Ron disks.



            Sur-Ron replacement connectors:

            Charger connector

            You would like to use your charger (at your own risks), the charger connector is a CNLINKO LP-20 series

            Male charger Plug: LP-20-C03PE-01-001
            Female battery Socket: LP-20-J03SX-01-001

            You can purchase them at NLINKO through Amazon.

            Discharge connector

            They are RCproplus dc-6.

            Last edited by Sebz; 09-28-2022, 02:34 PM.


              Ebrakes: More Detail

              The ebrakes are a sensor that is installed by the brake lever via a screwset.

              When installing it is VERY easy to rip out the ebrakes, which is the cause of most 'DOA' issues or intermittent working issues. Try fully unplugging to troubleshoot.

              Here is a video showing how they work and how to adjust them

              Below shows the sensor itself where it plugs into the lever, and the other side of it where it plugs into the white connector on the bike (these are from a Sur-Ron).
              The hex bolt that the sensor enters sets the depth, and the set screw keeps it fixed in position.

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              Here we can see a closeup of how the sensor actually goes through the bolt.

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              Side angle and a view of one of the sensors fully removed.

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              How to unplug the brake cut off sensor connector

              Open battery lid slide the breaker across to OFF and remove the battery.

              Remove the 2 screws that hold in the ignition and usb.

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              Gently remove ignition to access the wiring harness for the brake cut offs.
              Trace the wires from the front and rear brakes. These are the 2 wires marked with red arrows. Unplug them.

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              Gently remove the required brake cut off wiring and you are done.
              (Black arrow is pointing to the head light plug)
              Last edited by Sebz; 08-16-2023, 06:12 PM.


              • deserthi
                deserthi commented
                Editing a comment
                I unbolted the ignition but could not get it off. It simply would not come out. I feel like such a klutz!

              • paxtana
                paxtana commented
                Editing a comment
                Typically on these types of connectors there is a tab that latches it into position, you may need to move the tab to unplug it.

              • ElectricMud
                ElectricMud commented
                Editing a comment
                Can I just disconnect the two terminals and leave the cables attached to the brake levers? Is it necessary to take the wires completely off? Does it matter if the wire is removed from the brake lever since it would already be disconnected to the power source?


              Upgrading to riser bars

              Default stem clamp will hold 31.8mm bars
              If you need a riser handlebar we got you covered:
              To use a different diameter bar you would need to change the stem or use shims.

              What ever you do don't use adjustable stems to raise the bars, it's a serious safety risk for such an heavy bike... If this riser bar is not enough, use a downhill rated fixed riser stem or find a direct mounted stem with a all metal riser block under it.

              Click image for larger version

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              Last edited by Sebz; 03-11-2022, 10:18 AM.


                Adjusting the rear wheel and chain tension

                You will need proper tools to get the job done properly:

                1) 17mm socket and wrench
                2) 2x 10mm open end wrench.
                3) Measuring tape, ruler, micrometer or else.

                Click image for larger version  Name:	IMG_2677.JPG Views:	1 Size:	1.80 MB ID:	74784

                First step is to put the bike on a stool or a work bench, loosen up the rear axle, it's pretty tight so have someone holding the bike!

                Next step is to loosen up the 2 axle adjusters (on on each sides)
                To do so you just have to turn the locknut counterclockwise (lefty loosy) that should free up the bolt and the locknut

                locknut is the one with the chrome 10mm wrench
                The tensioner bolt is the one with the black wrench

                Click image for larger version  Name:	IMG_2683.JPG Views:	2 Size:	1.34 MB ID:	74785

                Now the important part is that you need to adjust the axle to get proper tension on the chain while keeping it straight.

                There are notches on the frame near the axle so use them to get the wheel straight.
                Work slowly by adjusting each side little by little till you get proper tension, what is proper tension.. about 1/2 ich to 3/4 inch slack
                When you have proper chain tension check the alignment of the wheel,You can use a ruler to measure the distance between the rim to the frame or use your hawkeye like I do :)

                Here you can see I pull on the chain to get to the zero mark and then pull the chain up to see if I'm between the safe slack range.
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                How I center the wheel to the bike
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                Once you have proper alignment and chain slack you must lock the tensioner in place, if you don't it will likely be all loose after your next ride.

                Hold the bolt in place with the black wrench then turn the lock-nut clockwise with the chrome wrench till the nut to set to the frame and tight.

                Recheck the chain tension again, pull hard on the chain to be sure if the axle is sitting on the tensioner. If you got more slack you will have to redo it again.

                Click image for larger version  Name:	IMG_2683.JPG Views:	2 Size:	1.34 MB ID:	74788

                Once it's locked on place it,s time to get that 17mm socket an wrench and firmly secure the axle, it's a large diameter axle so you can put a lot of force on it.


                  Replacing the throttle

                  2017 to early 2020 models:

                  The stock throttle is a cable throttle like any little dirt bike or pit bike, it is compatible with Honda CF50 throttle and etc...

                  If you do not wish to use the stock Sur-Ron throttle, you can get one for cheap from Ebay or else (See link for an example)

                  To remove it
                  1. You will need to pull out the grip or cut it off from the tube.
                  2. Turn the cable adjuster clockwise all the way in.
                  3. Unscrew the 3 bolts holding the throttle, remove the tube and cable guide
                  4. fully remove the cable adjuster from the the throttle body.
                  5. Install the new throttle
                  6. adjust the throttle properly.
                  7. Install a new grip or the old one
                  8. If the new grip is loose you can use rubber glue and safety wire to lock it in place (see pic below)

                  Once done it should look like this:

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                  Video of the throw with this throttle

                  For the newer 2020 models you can convert back to the old mechanical type which is likely superior, more robust and better throttle feel (with the metal throttle handle upgrade which reduced the throw to about 1/5 turn )

                  You will need a aftermarket pit bike throttle like the blue one up there, you can use the cable that is included with the throttle it's long enough. If you are getting you're throttle handle elsewhere make sure it's a 900-950mm cable.

                  You will need also a cable anchor because the throttle cable does not come with one, the barrel diameter is 6mm (1/4") so I bought a kit similar to this : Click here

                  And you will need the throttle box : You can get one from Luna but we are often out of stock on them

                  Click image for larger version

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                  Or maybe try Aliexpress here , or other Sur-Ron dealers across the globe

                  Last edited by Sebz; 01-11-2021, 07:02 PM.


                    Replacing/locking the grips

                    Stock grips are 7/8 inch grips (or 22.2mm) from the factory. Mine were already slipping after a wet ride so I had to do something.

                    Our friend Mark K told me about using safety wire to make sure they don't come out so I can say now that I tried it, Iwill never ride without them.

                    Here is a great video on how to replace your grips and how to lock them in place.

                    Oh and while you are at it get some grip donuts and say bye bye to thumb blister

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                      Adjusting the front fork

                      The Sur-Ron uses a basic downhill mountain biking type of fork

                      One of the fork leg has the spring (can be a real metal coil or can be an air spring) Depending on the model: FastAce, RST Killah, DNM USD-8S.

                      If your fork is a an Air type you will have to buy a fork pump to add some air to it for you weight and to get proper sag, search on Youtube for setup sag on a air fork. If it's a spring type you will either have to deal with the stock spring rate or try to find a springs from another fork manufacturer (like Fox, Manitou and etc). Spring or Air both have their own pro and cons but both are effective!

                      The other fork leg is the damper, on any basic fork you will find a compression adjuster and a rebound adjuster.

                      Compression (Low speed): regulates the force that moves a fork or shock through its travel. Compression damping is achieved with fluid, usually oil. This oil circulates through a compression circuit, and by restricting its flow, the suspension can be made firmer and can even be almost locked out.

                      So basically the more you turn the knob the harder it will be to compress the fork. Ultimately you can use the compression knob to firm up the spring (ie: to prevent bottom out) You can dial it down when you need a super plush ride for comfort.

                      Rebound: Rebound damping regulates the speed at which your fork or shock recovers, or bounces back, from an impact and returns to its full travel.

                      So rebound is the opposite of the compression, Too slow and the fork wont have time to recover for the next hit and will start to pack up and eventually you will have no more travel :) Too fast and the fork will bounce you back and you will loose traction.

                      What is my ideal setting? well you will have to find out yourself, rider weight, speed, riding style and the terrain will all play a role. It’s important to remember that suspension is intended to maximize traction; it does this by keeping your rubber in contact with the ground.

                      Some say start in the middle or the adjustments while others will tell you to start from 0, either ways are good just need to take the time to setup your fork properly.


                        Need to make a key copy?

                        Click on the pic to enlarge.

                        Ilco X121 DC3 for the Sur-Ron that came before mid 2019, after you would need a locksmith to make a copy or replace the whole ignition.

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                          Setting up the rear shock

                          The shock (either the DNM or the Fastace) like the front fork has a rebound adjustment and a compression adjustment. these work the same way as the front fork and need proper setup, please read the fork setup guide.

                          FYI: DNM takes a Fox sized coil 36mm inner diameter, the FastAce takes a RockShox sized coil 38mm inner diameter.

                          What differs from the fork is the spring pre-load adjustment and this is what we will cover here:

                          Your Sur-Ron light bee is probably set at the loosest setting possible so it's important to check the rear spring.

                          By this I don't mean to say to tighten down the spring a lot, too much pre-load will make the ride harsh and will require too much force to move the shock. If you are too heavy for the spring (just by sitting on it you get over 35% sag) or that you jumps cliffs for a living and bottom out on the stock spring then best would be to change the spring rate to get the proper sag and proper pre-load.

                          Lift the rear wheel up and sit the bike on a stool or a box. Grab the spring if you can move it or if you can turn the lock nut over the spring with your bare hand then it's too loose, But If you can rotate the spring and not the lock ring with your hand it's likely OK.

                          If you only need to tighten the lock-ring 1/2 turn or a full turn you can do the caveman technique and use a big flat-head screwdriver and hammer, be gentle you don't want to dent the lock ring. I personally used this technique as I only needed about 3/4 of a turn. Proper sag should be around 20% of the full travel, I weight about 170lbs with gear and I get good enough sag without much pre-load.

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                          If you need to apply more than just a turn then maybe it's best to remove the rear shock and use a locking ring spanner wrench.

                          Click on the pic to enlarge.

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                          Thanks Jonathan B for detailed instructions.
                          Last edited by Sebz; 11-16-2020, 01:37 PM.


                            Picking the right front fender for your Sur-ron

                            The surRon comes with the RST fork or the DNM/fastace inverted forks.

                            For the RST you can use any mountain bike fender you like, under the cross brace or under the front crown

                            But if you go for a "under the front crown type" you will need to check if that the cross brace clears the fender when it's fully compressed or you will break it right away,

                            Picture below is a Topeak Defender FX fender kit, it clears the cross brace fine and installs in minutes.

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                            If you dont like that style you can go for the "under the cross brace type"

                            like this one from Mark K, he used a
                            Mudhugger Long Front Fender

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                            Here is an installation video on modding mx fender for rst

                            If you have the inverted type you cannot use a over the tire fender because you don't have a cross -brace, so you will need a fender that is fixed under the lower crown like the Topeak shown. Since you don't have to worry about the cross brace hitting the fender you can use any mini-motocross fender you like but you will likely have to fabricate a mounting plate.

                            Picture is a Topeak defender on the RST fork, but can be fitted on the inverted forks.

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                            Another option: topeak defender xc1

                            DNM Fork users ONLY:

                            We have stocked this fender which will work and is a more ideal solution than the topeak defender fork:

                            Distributors and builders of high power electric bikes and trail bikes plus parts

                            Last edited by paxtana; 07-05-2021, 05:35 PM.