Empulse Powertrain Lash

Riders who are new to the Empulse will notice a jerk when starting the bike from a stop. This is sometimes referred to as "the clunk", but the correct name is "powertrain lash". This page will discuss the causes, and techniques to minimize the lash. It should be stated that the lash is part of the normal operation of a motorcycle transmission and not an indication of a problem with the bike.

Causes

In a post by Brian Wismann on the Brammo Owners Forum, he indicated that the powertrain lash is "typical motorcycle transmission backlash that is being felt. It is amplified to some extent because:

1. The electric motor does not idle like a gasoline engine.

2. We instruct riders not to slip the clutch during launches for the best performance.

3. There is no engine vibration damping the feel of the lash being taken up."

He posted the following three videos in an effort to explain the issue visually:

• Triumph Street Triple Gearlash:

http://www.youtube.com/watch?feature=player_embedded&v=yKlsInsP7r0

• Empulse gearlash:

http://www.youtube.com/watch?feature=player_embedded&v=9SZkPI4HUnU

• Gearlash internals:

http://www.youtube.com/watch?feature=player_embedded&v=mn2p_hYX0io

Remedies

Rollback

When the bike is stopped, push the bike back until you feel the transmission engage. Note that this will be about 6 inches (15 cm), and the feeling of the transmission will be very subtle. Engage the brake and you will be ready to start without any lash.

Dragging the brake

Similar to regular ICE bikes, dragging the rear brake when going at low speeds will mitigate powertrain lash.