Thunderbike Engineering

Fitting Instructions
Thunderbird 1600/1700 Fork Cap Kit

IMPORTANT Your forks and their clamping yokes are safety critical components. If you are at all uncertain of your ability to fit this product yourself please seek assistance from a trained professional.
  1. Loosen the fork clamping bolts on the top yoke and loosen the fork cap. Don't remove at this stage. Use a piece of plastic/rubber over the hex of the fork cap to save it from damage by your socket/spanner.
  2. Lift the front end of the bike so no weight is on the front wheel and the forks are at full extension.
  3. Remove the fork caps taking care to hold them firm as there will still be pressure under them from the springs.
  4. Remove the o-ring from the fork cap and re-fit onto the Thunderbike fork cap.
  5. Re-fit the Thunderbike fork caps. This is the trickiest part of the process with quite a bit of force required to hold the cap down while screwing it in. The thread is a fine pitch and you are screwing Aluminium into Steel so take care to line it up. If the thread starts to bind stop, unscrew it, check for burs, clean up if necessary and start again. Don’t force it in.
  6. Loosen off the fork clamping bolts on the bottom yoke and the clamping bolts on the indicators.
  7. Carefully slide the forks down through the yokes until the fork cap is flush with the top face of the top yoke on both legs.
  8. Tighten up the fork clamping bolts on both yokes and the indicators.
  9. Remove the two bolts holding the brake line bracket to the underside of the bottom yoke.
  10. Pull the brake line out from the cable clip at the top yoke to allow a little extra slack.
  11. Refit the brake line bracket with the supplied spacers between the brake line bracket and bottom yoke and use the supplied bolts to tighten it back up.
  12. Double check your work before going for a ride! The ride and handling characteristics of your bike will have changed so take it easy and familiarise yourself with the new feel.

Torque Figures

Upper Yoke Pinch Bolt 20Nm
Lower Yoke Pinch Bolt 27Nm
Fork Cap 22.5Nm
Brake Line Bracket Bolt 6Nm
Indicator Bracket Bolt 18Nm
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