when bumping, the engine tends to turn over faster than by boot leather, which, due to the higher signal strength means it will generally start with an air leak.(boot, main seals, cases etc). as the signal strength is lower when kicked, the air leak will make sufficient difference that she won't go by kicking.had this prob myself before i got into strokers on an addicted level.the cracked boot if admitting unmetered air would be enough to cause 'no ride today' frustration. however, I would advise, after sorting the boot issue, to do a pressure and vacuum test to make sure its not leaking anywhere else.as I mentioned 86 air boots are rare in good nick, and due to the mk1 rear suspenders, the 86 boot is a straight shot, and the 87 on arent, due to differing shock location as opposed to the mk2(87 on) uni trak system.if the liquid rubber suggestion is no good, I would consider asking jfab or larry to do you a new one in ally.hth, K.