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Main Area => General GS500 Discussion => Topic started by: octane on November 06, 2003, 11:48:46 PM

Title: Carb Vacuum Question
Post by: octane on November 06, 2003, 11:48:46 PM
Short synopsis...pulled carbs off, installed K&N pod and stage 3 jet kit with V&H exhaust. Bike runs ok at first, but quickly becomes temeramental. Bike stalls on highway. Starts again, rides a mile or two and dumps some fuel (left side of bike if that matters). Oil looks ok, but smells like gas - so I change it. Pull tank, get bike running (albeit a little rough), hear vacuum leak. On the bottom right of each carb is a small vacuum port. The right carb plugs into the vacuum hose on the petcock - left is wide open. I plug the left carb vacuum port and everything smooths out. Is this correct or did I forget to install something when I put the carbs back on? (They were off for a few months...I may have missed something) Thanks in advance.

P.S. - A local shop is having a dyno day on Saturday morning and I want to see what the little GS will pull. I'm gonna get spanked by all the gixxers and cbr's - but the $20 fee goes to the childrens hospital...
Title: Carb Vacuum Question
Post by: miket on November 07, 2003, 12:08:55 AM
On my '93 the vacuum hose goes from the top of the left carb to the petcock. I don't remember any vacuum port on the right carb. Unless you're talking about the synch ports, but those should have a rubber cap on top.
Title: Carb Vacuum Question
Post by: Blueknyt on November 07, 2003, 01:22:08 AM
sounds almost like either too rich or float lvl too high/sticking sure you didnt drop a jet, ive had mine vibrate off once.
Title: Carb Vacuum Question
Post by: Jared on November 07, 2003, 07:46:12 AM
That vacuum port is normally plugged or closed (on right side carb)- They just make the one carb body ....so they plug the one that is not used for the Petcock...You're probably just missing the little black rubber plug/cap....

Fix that and go from there....
Title: Carb Vacuum Question
Post by: Diderich on November 07, 2003, 07:51:07 AM
my '01 has the petcock connected to the right and the left has a little cap over it.  It is a little smaller than 1/4" i think...3/16" maybe?
Title: Carb Vacuum Question
Post by: octane on November 07, 2003, 09:25:54 AM
Hhhmmm...does it matter which carb the petcock plugs into? Should be fine as long as it's getting vacuum, right? The diagram I had looked like the petcock plugged into the right carb, so I just plugged the left one. Seems ok now, but I wanted to make sure it's right before I put it back together. I friggin' HATE taking the tank off. Dyno day tomorrow!! Thanks for the help guys.  :thumb:
Title: Carb Vacuum Question
Post by: bob on November 08, 2003, 07:20:10 PM
Hey, Octane,
It's now tomorrow evening...  :?
Didja get'er running OK?  Didja do the dyno run?  How'd the ol' gal do?  How many horsepuppies she make?
Title: Carb Vacuum Question
Post by: octane on November 09, 2003, 03:59:52 PM
Nah, one problem after another...I fiddled with it until 4:00 and then drove my truck to the shop to see some of the other guys run and ask the mechanic what his thoughts were. He's suspecting a float needle problem too, but I haven't had time to pull the carbs again.

There were some sick bikes there though - top HP of the day was put down by a HIGHLY modified 'Busa. 227 hp at the wheel!!!

When I get it all figured out and running right I'll put 'er up on the dyno though. Hopefully soon.
Title: Carb Vacuum Question
Post by: octane on November 10, 2003, 06:55:12 AM
One other question...I've obviously been messing with the carbs and making no progress, but now the bike is backfiring like mad. Is that a synch problem, mixture problem, or did I go ahead and mess up another adjustment while I was at it! Thanks again.
Title: Carb Vacuum Question
Post by: yamahonkawazuki on November 11, 2003, 02:24:03 AM
hmmmmm, starting to sound like a rashad novel :mrgreen: , btw did you mess with the mix screws any? :cheers:  :thumb:
Title: Carb Vacuum Question
Post by: octane on November 11, 2003, 07:54:50 AM
Turned them out exactly like the Dynojet instructions said - 2x if I remember correctly. It didn't start backfiring until I started messing with the idle and synch screw though...I think.