Transmission Undercutting – ‘Road Race Cut’


We only undercut transmissions for the motorcycles listed on our website, we do not do one off or any other makes or models. Please refer to the description for the official list.

*Additional shipping charges apply for this item.

*Transmission undercutting is a service to modify your OEM transmission.  You must remove your transmission and ship it to us for undercutting service.  We will inspect all gears upon dis-assembly and let you know if any gears should be replaced before undercutting.  New OEM spring clips may be required for re-assembly.

*Allow 2-4 weeks for turn-around.


Ever shift up into 5th gear coming on to the straight-away only to have your bike drop back into 4th gear on it’s own??

Transmission undercutting is standard procedure for top race teams.  It is the only way to completely eliminate the problem of your motorcycle accidentally dropping out of gear under acceleration or deceleration.

We offer a “Road Race Cut”, where both sides of the drive dogs are cut to ensure the the transmission will not drop out of gear during acceleration or deceleration.

What is transmission undercutting?

Motorcycle transmissions operate by a series of gears with drive dogs and/or slots that are engaged or disengaged when the gears are shifted.  When a particular gear is engaged, it’s drive dogs are meshed with the gear next to it to transfer power.  With many less expensive motorcycles, these drive dogs and receiving slots are square in shape, and can slip free under acceleration or deceleration, causing the transmission to involuntarily shift gears or find a place between gears called a “false neutral” where no gear is engaged.  “Undercutting”, or “back-cutting” is a process where these square shaped drive dogs and slots are cut at a small angle, so that when they are meshed together, the power applied to them actually forces them together and it’s impossible for them to slip free while under load.

Motorcycle Transmission Undercutting Explained


Bikes we can undercut:

  • Kawasaki Ninja 400 / Z400 (All Years)
  • Yamaha R3 (2015+) / MT-03 (2019+)
  • Yamaha R7 / MT-07 / FZ-07 (All years)
  • *Coming Soon* Aprilia RS660 / Tuono 660

Additional information

Weight 6 lbs
Dimensions 9 × 6 × 6 in


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