hi folks, need a little help here. here's the story, feel free to skip down to paragraph 3 for the actual question.
ok, so this is my 2nd bike and first XS650. i'm a mechanical engineer, so naturally, i don't know crap about actually being a mechanic. i'll just put that out there right now. anyways, bought this '79 special from a local guy who builds street trackers out of these bikes. this was a project a friend/client brought to him that he had started working on but ended having to sell. by the time i got it, he had rewired it, put a different tank on it, put a pamco ignition system on it with new plugs and wires, welded an open exhaust on it and put a set of the 80-84 34mm carbs on it. it started on the 1st kick the first time i went to look and again on the 2nd time. the day i bought it, it wouldn't start for like 15 minutes. we figured, ok, it's out of fuel. put fuel in it and somehow got it to start. i ride it from his place to work, where i turned it off. it promptly decides to leak fuel through the carbs out the air box and onto the frame from both sides. long story short i eventually figured out (i'm a carb n00b) that the floats were stuck and the petcock was toast and gave the carbs a wack. that takes care of the fuel leak. but now it still wont start. i took the battery home and charged it overnight. took it back later that week, put the batter back in, put some new fuel in it and BAM! starts on the 2nd kick.
i'm not brave enough to take it on the on the freeway like this so i went around the top of the lake on the surface streets. it's running fine. then it starts backfiring. dies, won't start and run for more than 100 yards, etc. got it towed home, blah blah, consulted the internet and of course it's the charging system just went out. no problem. because i was too cheap to do the banshee mag swap right now and i wanted this thing for a commuter, i just got a rotor off of ebay and swapped that + the brushes. new battery and i'm good to go, right?
weeeeeellll, now i come to the problem at hand. i know this thing was running fine before i replaced the rotor and battery because i started it and let it run on a fresh charge in my driveway for 15 minutes while i let the last of the fuel burn off. it sat there and idled just fine. however, now i cannot get it to stay on. here's what i do:
i can sit there with the choke pulled all the way out and play with it for about 5 minutes without the engine dying, but after that, it will just cut off. it doesn't matter what position the choke is in. the cylinders are warm to the touch. if at any point, i try to twist the throttle (with or without choke), the revs drop and it dies. if i start it again, it will usually die within a few seconds of starting, no matter what position the choke is in. i tried increasing the idle, but even all the way down, the engine will still cut out.
i'm at a loss. i pulled the plugs. they're pretty dark, sooty, but otherwise fine. the only other thing that i have to offer is, the first time i tried to start it up today, there was some smoke coming out of the right carburetor. somebody told me i might have a burnt valve on that side now, but all of the backfiring when the charging system went was on the left (oddly enough).
at this point, i'm thinking it's a carburetor problem. i know i should pull them off, clean them, etc, but i'm pretty sure they were already reworked before i got the bike and honestly, i don't want to take another week to get the stupid thing running. any ideas?
ok, so this is my 2nd bike and first XS650. i'm a mechanical engineer, so naturally, i don't know crap about actually being a mechanic. i'll just put that out there right now. anyways, bought this '79 special from a local guy who builds street trackers out of these bikes. this was a project a friend/client brought to him that he had started working on but ended having to sell. by the time i got it, he had rewired it, put a different tank on it, put a pamco ignition system on it with new plugs and wires, welded an open exhaust on it and put a set of the 80-84 34mm carbs on it. it started on the 1st kick the first time i went to look and again on the 2nd time. the day i bought it, it wouldn't start for like 15 minutes. we figured, ok, it's out of fuel. put fuel in it and somehow got it to start. i ride it from his place to work, where i turned it off. it promptly decides to leak fuel through the carbs out the air box and onto the frame from both sides. long story short i eventually figured out (i'm a carb n00b) that the floats were stuck and the petcock was toast and gave the carbs a wack. that takes care of the fuel leak. but now it still wont start. i took the battery home and charged it overnight. took it back later that week, put the batter back in, put some new fuel in it and BAM! starts on the 2nd kick.
i'm not brave enough to take it on the on the freeway like this so i went around the top of the lake on the surface streets. it's running fine. then it starts backfiring. dies, won't start and run for more than 100 yards, etc. got it towed home, blah blah, consulted the internet and of course it's the charging system just went out. no problem. because i was too cheap to do the banshee mag swap right now and i wanted this thing for a commuter, i just got a rotor off of ebay and swapped that + the brushes. new battery and i'm good to go, right?
weeeeeellll, now i come to the problem at hand. i know this thing was running fine before i replaced the rotor and battery because i started it and let it run on a fresh charge in my driveway for 15 minutes while i let the last of the fuel burn off. it sat there and idled just fine. however, now i cannot get it to stay on. here's what i do:
- turn on choke
- kick start (usually 2-3 tries)
- sit while with the choke on for 1-2 minutes while the engine revs between 1-2.5k. i have to sit there and keep my hand on the choke or it retracts and the engine dies.
i can sit there with the choke pulled all the way out and play with it for about 5 minutes without the engine dying, but after that, it will just cut off. it doesn't matter what position the choke is in. the cylinders are warm to the touch. if at any point, i try to twist the throttle (with or without choke), the revs drop and it dies. if i start it again, it will usually die within a few seconds of starting, no matter what position the choke is in. i tried increasing the idle, but even all the way down, the engine will still cut out.
i'm at a loss. i pulled the plugs. they're pretty dark, sooty, but otherwise fine. the only other thing that i have to offer is, the first time i tried to start it up today, there was some smoke coming out of the right carburetor. somebody told me i might have a burnt valve on that side now, but all of the backfiring when the charging system went was on the left (oddly enough).
at this point, i'm thinking it's a carburetor problem. i know i should pull them off, clean them, etc, but i'm pretty sure they were already reworked before i got the bike and honestly, i don't want to take another week to get the stupid thing running. any ideas?
(hint: RG, whose post is just above mine)... do NOT ride this bike without a voltage gauge mounted to the bar. You want to know what your charging system is doing at all times. They are cheap and easy to mount. It does sound as if you have a fuel issue here, but remember too that as your bike sits idling, it's basically running off the battery until the rpms come up; engine speed on these bikes has everything to do with what the charging system is doing at any given time. I just don't want you to do what I have done... develop a low battery condition that masquerades as a fuel issue.
