When the first generation of K-40s and K-400s was made,  the O-rings  seemed to work well...  As time went on it was discovered that if the pumps were inactive or used infrequently, the lubrication migrated into the O-ring material causing it to shrink. The shrinkage translated into a lack of seal and pumps that leaked air.  As soon as this was discovered we embarked on a mission to find O-rings that were not adversely affected by the lube...  After numerous tests it was discovered that there simply wasn’t anything available at any cost.  So, we had our own made.  The new O-rings are constructed of a proprietary material and made to different  size and softness specs.  The new O-rings have solved the problem completely. 

For anyone who has a K-40 or K-400 that suspects that they may have a problem with the large O-ring, we will send you replacement rings at no charge for the balance of 2007.  All we need is “proof of purchase”. A word of advice... if you’re on a trip and your pump starts to act up in the manner described above:   disassemble the large pump body... (the set screws are located where the blue webbing material is attached to the pump) and remove the O-ring that is on the plunger.  Clean it off and then grasp the ring with your thumbs gently exert pressure until the ring is in an sharp “oval” shape.  Then STRETCH the O-ring an additional one or two inches.  The O-ring will be slightly oversize and “floppy” but it will work very well if you  if you carefully re-insert the plunger assembly taking care to make sure that the ring stays in it’s appropriate groove...  It’ll work great!   When you get your new rings, replace the ring on the plunger and the spare that is located in the bottom of the pump body.