1. Requirements
  2. Pay attention
  3. Mechanical installation
  4. Configuration and live test


This guide assumes that you have already reviewed Stokemonkey’s compatibility notes ( to assure that things will fit, and are prepared to address any side issues like shifter/throttle ergonomics that your bike may present.

You will need the following items:

  • Crank puller and crank bolt wrench
  • Pedal wrench
  • Metric hex wrenches in the common bicycle sizes (L type recommended)
  • 8- and 10-mm wrenches (or adjustable crescent)
  • Needle-nose pliers or fourth-hand tool
  • Cable cutter

In some cases you will also need the following items, or find them useful:

  • Bottom bracket installation and adjustment tools
  • Chain tool
  • Rubber mallet, dead-blow, or similar like a hammer and block of wood to deaden strikes
  • Torque wrench
  • Utility knife
  • Hacksaw for kickstand length adjustment due to balance of battery
  • Grease

Pay attention

  • Never, ever work on Stokemonkey while the battery is connected! Don’t let the silence give you a false sense of security: we still have all our fingers, but more than once have found ourselves wrestling large animated bicycles as parts fly because we forgot it was live! Charge your battery while you perform the mechanical installation, and forget about hooking it up until you are finished.

  • The wires between motor and controller are delicate. Never pull or bend them sharply. Take care to keep them clear of any moving parts during and after the install. Zip ties are your friend.

Mechanical installation

  1. stay clearanceRemove the existing cranks and install the replacements. Confirm that the left-side chainring is far enough out for the lower run of the motor drive chain to clear the chainstays, as indicated in the diagram at right (shows right-side clearance, but the same test applies to the left).

    If there isn’t sufficient clearance, you must create it by any or all of the following means:

    • Removal of any right-side bottom bracket spacers
    • Addition of left-side chainring spacers
    • Substitution of a longer bottom bracket spindle
    • Substitution of an alternative left-side spider with higher chainline
    • Substitution of a bicycle frame with narrower chainstays.

    Stokemonkey requires a left-mounted spider and chainring of approximately 44 teeth. Clever Cycles provides quality replacement cranks for square-taper bottom brackets. You may substitute a tandem-specific left spider or even a spare right-side spider on the left side if desired. If you use a right-side spider, you will need a second right pedal, and must apply a thread-locking compound to the pedal threads to prevent it from unscrewing in use.

  2. The mounts are pre-assembled for clarity and packing ease. Disassemble the aluminum clamp by removing the bolts, and study how the tension cable is assembled before loosening the rear cable retainer nut on the steel bracket arm to open the loop. Leave the front cable retainer bolt tight.

    These instructions first discuss mounting for the Xtracycle FreeRadical. If you are installing on a Surly Big Dummy, Yuba Mundo, or Xtracycle Edgerunner skip ahead.

    Mount for Xtracycle FreeRadical

    Assemble the mount around the Xtracycle’s top stay as shown, square with the bike. Do not tighten the bolts — just take up the slack in them. You should be able to adjust the position of the clamp on the tube easily.

    Mount for Surly Big Dummy

    This section is for Big Dummy mount installations only. Skip ahead to the next numbered step if you are installing on an Xtracycle FreeRadical.

    Remove the cap-head bolts from the Big Dummy’s rear bottle cage mounts, top and bottom.

    Place the shims as shown to clear the bottle cage bosses. You may have to adjust the position of the shims on the stay in later steps; the initial position is not critical.

    Replace the cap-head bolts with pan-head ones (provided) to prevent water ingress.

    Assemble the mount as shown, square with the bike. Do not tighten the bolts — just take up the slack in them. You should be able to adjust the position of the clamp on the shims easily.

  3. Put the chain loop on the motor freewheel, and fit the motor axle into the steel bracket as shown. Many people are surprised to discover that the external case of the motor rotates in use. This is normal. The motor has no internal moving parts: the motor rotor is the case.

    Note function of the sprocket pinch guard (piece that looks like a bottle opener) as an axle retainer washer.

    Assure that the motor wires are pointing down as they exit the axle. (This is so water won’t drip along the wires into the motor.) Tighten the allen bolts in the ends of the axles to fix the motor in the bracket, assuring that the axles are completely seated in the bracket slots.

  4. Turn the bike upside down. Put the chain onto the left-side chainring, and nudge the motor bracket in the clamps to make the chainline roughly straight. The motor will be offset to the left side. Tip: remove your Xtracycle’s seatpost and it will stand squarely upside down on the ground on the handlebars (on a towel or similar pad) and v-racks, with more stability than in many bike stands.

    Nudge the whole assembly as required so the motor clears all adjacent members, with the motor body approximately 1cm (3/8”) from the rear of the seat tube, and correct drive chainline (in a single plane with the gears). With some bikes, you may need to remove or add links from the drive chain to position the motor correctly. A rubber mallet or block of wood and hammer may be helpful in tapping the mount into position without having to loosen the bolts too much. Rotate the pedals backwards to turn the motor and check for quiet, straight engagement of the chain with the driven and driving gears. Check also to assure that the whole assembly is square, with the motor sides parallel to the seat tube.

    Lightly tighten the clamp bolts and check again. This is an iterative process of loosening and lightly tightening the clamp bolts enough to allow adjustment while assuring that the chainline and clearances are correct when the clamp bolts are tighter.

    As you lightly tighten the clamp bolts, aim for uniformly square gaps between the clamp plates. High precision is not required — just eliminate readily visible departures from the square and the straight.

    When the assembly is in final position, tighten all clamp bolts gradually and evenly to keep the clamp plates parallel, finally tightening until they begin to chirp or 6.2 Nm torque, whichever comes first.

    Check the drive chain tension with your fingers. There should be no slack in the chain, but it shouldn’t bind at any point of the rotation, either. This is the ideal chain tension that we will strive to achieve at the end of installation, and again at service intervals to address wear and relaxation of the tension cable assembly.

  5. Turn the bike upright, and check the drive chain tension again. The weight of the motor alone may have led to enough flex for the drive chain to have sagged a small amount; this is normal. The goal of the next steps are to remove any chain sag, and help maintain correct chain tension as the bike flexes in use.

    Loop the tension cable assembly around the seat-stay bridge as indicated.
    Several loop variations are acceptable as long as the cables clear the motor body, and the loop is not subject to slipping down the seat stay under tension. The tension cable should ideally be anchored around a point perpendicular to the line between the motor axle and the steel bracket’s clamped tube.

    Pinch the cable housing ends together and hook the front cable span with the cable yoke fastened to the rear cable span. The cable yoke should be cinched up to touch both ends of the cable housing.

    Push the rear cable end through the retaining bolt on the mount arm. Pull it taut with pliers or a fourth-hand tool, using the bottom edge of the bracket arm for leverage if necessary. Take care not to mangle the cable for at least an inch below the retainer bolt. Tighten the retainer bolt when all visible slack is gone from the cables, the housing loop conforms tightly to the chainstay, and the chain tension feels too tight. Be careful not to over-tighten the cable retainer bolt; you can easily damage the cable. If you need to replace or lengthen, it’s ordinary brake cable.

  6. Firmly grasp both sides of the motor drive chain with your hands, and squeeze tightly together repeatedly, watching for any settling of clamps or tension cable. Your goal is to test the tightness of all fasteners and stress the assembly enough to leave the tension cable and the chain feeling slack. This process is somewhat analogous to stress-relieving a spoked wheel as a means of achieving stable spoke tension.

    If required, retension the cable by loosening the rear retainer bolt and pulling the cable taut again.

    Repeat the chain squeezing and cable tensioning steps until the squeezes no longer leave the chain feeling slack.

    Cut the cable a couple inches below the retainer bolt. Cap the cable end to prevent fraying.

    Check the cable tension again after the first few dozens of miles of use; retension the cable further by sliding the yoke down the cable spans as shown, and gently tightening the yoke nut to hold it in place.

  7. Press the bottom end of the pinch guard to bend it inward, to prevent wayward trousers and the like from getting sucked into the juncture of sprocket and chain.

  8. Mount the throttle on the handlebar (left side is default version). Operate the throttle to assure smooth action and a quick return to the off position. Do not overtighten the throttle set screw, lest it interfere with quick return to off. Re-install adjacent controls and grips such that they will not interfere with throttle operation. This may entail replacing or modifying parts, in some cases.

  9. Mount CycleAnalyst for Stokemonkey as you would any other cyclocomputer, installing the spoke magnet and sensor on a fork blade, and zip-tieing any excess wire cleanly out of the way.

    Route the throttle and CycleAnalyst cables cleanly toward the rear of the bike, perhaps parallel to the rear brake cable housing, assuring that they are not pulled as the bars are turned.

  10. Remove the Snapdeck and install the controller bag, securing it either to the V-racks or to the bike’s chainstays. Connect the motor, battery, CycleAnalyst, and throttle wires through the open bottom corners of the bag to their color-matched or pin-exclusive mates emerging from the controller. Gather and bundle any excess wire length and wrap it snugly in the velcroed flaps of the bag. Orient the controller such that the power switch can be operated through the soft top flap of the bag.

    Assure that all wires are secured with zip-ties to stay clear of any moving parts.

    This completes the mechanical installation.

Configuration and live test

Remove the bike from the workstand. Place the battery in the inner pouch of the Xtracycle FreeRadical or similar snug and secure location. Don’t simply lay it in the FreeRadical sling; it will be thrown around too much!

Connect the battery. Switch the controller on. CycleAnalyst should power up. If it doesn’t, check connections and try again.

Switch the controller off. Hold the button on the right side of CycleAnalyst while turning the controller on again. This enters Setup mode. Release the button.

Press the button to advance through the various configuration options. To change a value, hold the button until “OK” appears at the lower right of the display. Press the button to change the value(s), and hold the button to save and advance to the next value or configuration option. To fix mistakes, you must turn the controller off and re-enter setup mode to return to the screen.

The configuration options are:

  • Set units; values are miles or kilometers. Miles are the default.
  • Set wheel; circumference in millimeters. 2075 is the default, which matches a 2-point-something-inch tire on an ISO 559 (26″) rim. Enter the measured circumference or refer to an online chart ( for accurate speed and distance readings.
  • Amps limit; limits maximum power. Useful for extending range and conditioning new battery packs gently. Note that the controller itself (separate from CycleAnalyst) limits power to around 20A, so higher values are not meaningful.
  • Low volts limit; protects batteries from over-discharge by cutting power as voltage drops below a set figure. 31V is the default. The controller itself will cut power at 30V.
  • Main display; values are watts or amperes, for display purposes. Watts are the default, together with watt hours. Amps or amp hours are the alternative.
  • Lockout time; number of seconds of zero speed after which the throttle becomes inactive. This is a safety feature intended to prevent accidental throttle activation, and an efficiency feature intended to discourage using the motor as a substitute for downshifting at stops and pedalling normally to start. Note that in normal use while stopped, the throttle lockout can be overridden for the specificed interval by tapping the CycleAnalyst button. The default is 10 seconds.
  • Set #poles; the number of wheel magnets used. Adding magnets (and increasing this figure accordingly) can shorten the time speed is sensed from a stop and the throttle lockout lifted. The default is 1.
  • Clamp throttle; sets the maximum throttle value, useful in limiting power to extend range or to accommodate slower pedaling styles. Default is 100%.

If in doubt, we suggest you leave the default values as they are for now, with the exception of the Set wheel size.

Finally, ride the powered bike to test the installation. Pedal normally and assure that the braking and shifting is normal, and that there are no unusual noises before using the throttle. If there is no response, it is likely that CycleAnalyst’s speed sensor pickup is too far away from the spoke magnet, so no speed is detected. Adjust as required.