need some help diagnosing a fuel problem
my bike has had a recurring problem which i'd like to solve. about 50% of the time, the bike won't idle and will lose power and sputter at low rpm's. the other 50% of the time, it's absolutely fine and idles perfectly around 1500 rpm. when the problem is occurring, the bike displays all the symptoms of the 'phantom out of gas' syndrome, but i've tried opening the gas cap while the symptoms are occurring with no positive effect. if i slow down, the bike will die unless i keep the engine revved at about 3000 rpm. if it does die, it absolutely will not start until i use my magic trick.
the magic trick is removing the vacuum line which connects the petcock to the carbs. once i remove this tube (by disconnecting at the carb), i hit the start button and after about four turns, the engine starts and will continue to run. while it's running, i'll put the vacuum line back on the carb and the idle will instantly pick up (as now fuel is being actively sucked into the carbs). ok... good... and the bike will be fine for an indeterminate amount of time... maybe only a minute, maybe for half an hour depending on how fast i'm going... and then it happens again. the bike dies at low rpm's and won't start until i disconnect the vacuum line.
i use seafoam religiously and the carbs have been cleaned. the vent line going to the right side ear is cut at 45 degrees. the bike is a california model with two vent lines coming out of the gas tank. this past weekend i made sure that the left vent line which terminates at the gas cap was unobstructed... and now the bike won't start at all, even with the trick. doesn't seem like any gas is getting to the carbs. my plan was to eventually cap the right vent line and then just run a line from the left vent to the ground (bypassing the whole ca emissions thing), but yeah... the bike won't start now.
i don't know what is going on. seems like something simple, but i need some help.
any ideas? sorry for the long post.
Last edited by global_recon; 07-01-2009 at 02:11 AM.