Service Bulletin — Avinox M2 / M2S

Posted on By Derek Betcher

5DEV Service Bulletin — Avinox M2 / M2S

Fitting 5DEV ISIS Drive cranks to an Avinox M2 or M2S motor? Use this guide to work through fit problems at installation and keep track of the crank-to-motor connection in service.

The ISIS Drive interface is common to Avinox M1, M2 and M2S motors, but spindle dimensions on M2 / M2S motors can affect crank fitment. Reports from production assembly and aftermarket installations describe two possible obstacles. Identify yours before moving to the next section “workbench instructions”:

  • Cannot start the bolt? If pressing on the crank arm by hand leaves the threads out of reach, begin with “Establish bolt engagement.” Do not try to overcome this with torque.
  • Arm still short of its seated position? If the recommended 45 Nm does not bring it far enough onto the spindle, begin with “Verify seating clearance.”

To 5DEV’s knowledge, Avinox is aware of this dimensional issue. For now, the procedures below provide a way through most reported fit problems. They apply only to the crank and motor combinations identified under Products Covered.

 

Workbench Instructions

Establish bolt engagement

Thread engagement must come before tightening. When the crankarm’s hand-pressed position prevents the bolt from starting, reposition the arm as follows. Trying to draw it on with a bolt that has not fully engaged will damage the threads.

  • Begin by separating the crankarm from the motor spindle.
  • Take out the bolt and self-extractor cap assembly with either a cassette lockring tool or a pin spanner.
  • Lubricate both mating spline surfaces with grease: the motor spindle and the internal bore of the crankarm.
  • Return the arm to the spindle. Give it a few light taps from a rubber mallet.
  • Put the crank bolt back in, with the washer under its head.
  • Tighten the crank bolt to 45 Nm.
  • Finish the hardware assembly: fit the plastic washer over the bolt head and secure the extractor cap at its specified torque.
  • Bolt engagement is only the first check. Continue below to confirm the crankarm’s seating clearance.

 

Verify seating clearance

Confirm the crank seating by measuring the distance from the motor spindle clip to the crankarm face. If you measure 3.5 mm or more, proceed to the following grease-and-refit process:

  • Confirm both mating spline surfaces have adequate grease: the motor spindle and the internal bore of the crankarm.
  • With the arm fitted to the spindle, torque the crank bolt to 45 Nm.
  • Use the clip-to-arm measurement to decide the next action:
    • Less than 3.5 mm — no further reseating is needed; continue.
    • 3.5 mm or greater — take the arm off, re-check grease and refit to 45 Nm.
  • Take a fresh gap measurement every time the arm is refitted.
  • If you still see a gap above 3.5 mm after 3 installation attempts = STOP. Set the crankset aside and email info@5DEV.com for guidance before proceeding.

 

After installation: keep the fit under review

Think of the installed fit as something to revisit, not a one-time setting. With no hard stop on the M2 / M2S spindle, the crankarm relies entirely on bolt clamp load to stay in place. Time in use and repeated removal and refitting can move the arm farther onto the spindle.

Create a routine to check the following every ~200 miles or ~3 months, and again whenever a crankarm has been removed:

  • Verify the crank bolt’s torque is 45 Nm, re-torque if needed. If it is significantly less, re-start up at the “Workbench Instruction” section, and continue through verifying seating clearance and final torque.
  • Pay attention to the cranks while riding: creaking or play at the crank-to-motor interface are the signs to watch for.
  • If you hear creaking or find that the bolt will not retain its torque setting, reach back out to 5DEV for support at info@5DEV.com

 

Service Recap

Service handoff checklist

ü  Application — the listed 5DEV cranks paired with M2 / M2S motors. M1 and other ISIS Drive motor brands are outside this bulletin’s scope.

ü  Thread protection — correct the arm’s position when the bolt cannot reach the threads; do not force it to start.

ü  Seating targets — 45 Nm at the crank bolt and a gap below 3.5 mm. The limit is three attempts in total.

ü  Service routine — check torque and watch for creaking or play every 200 miles or 3 months and after each crankarm removal.

ü  Support — email info@5DEV.com before proceeding if the third attempt leaves a gap above 3.5 mm. Also contact 5DEV for creaking or a bolt that loses torque.

 

Products covered: The following cranks are included only when used on Avinox M2 or M2S motors:

·       R-SPEC ISIS Cranks

Products not covered: The following applications are outside the scope of this bulletin:

·       Cranks with ISIS splines, but used anywhere other than Avinox M2 / M2S motors

·       Cranks used on Avinox M1 motors

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