Current thinking is that the booster has dual diaphrams and I burst one during bleeding by hyper-extending the pedal. This explains why there is boost for the first 50% of the pedal travel. I have been stumped by this for over a year, and the correct answer (Elijah Scott) came within hours. Gotta love this list! I had been ignoring the booster because it was replaced in 2001 - only a few miles ago. Should have asked earlier. -Kenyon Kenyon Wills ----------------- http://www.imperialclub.com ----------------- This message was sent to you by the Imperial Mailing List. Please reply to mailing-list@xxxxxxxxxxxxxxxx and your response will be shared with everyone. Private messages (and attachments) for the Administrators should be sent to webmaster@xxxxxxxxxxxxxxxx To UN-SUBSCRIBE, go to http://imperialclub.com/unsubscribe.htm