Hello,

My 1980 Yamaha XS400 has a vacuum activated petcock. The vacuum line connects the petcock to the intake manifold. The vacuum line keeps undoing itself when I run the engine. I keep the bike stationary and idle the engine and over time (about 15 seconds) the vacuum line on the petcock end completely removes itself from the petcock nipple. Does anyone have any idea what can be causing this? If it helps, my intake boots are cracked and there is probably not a god seal (I have new ones coming in the mail).

Thanks,

Adam

renew the line and put a wire clamp in there to hold it over the nipple