I've got an 04 GS500F and am less than impressed with the performance.  It'll do just find for the purpose I bought it for (commuting-gas saver). I'm not interested in racing it, just a little more umph would be nice if I could do it simply without spending an arm and a leg.
 I've been reading about re-jetting on here and was currious on if it made much of a difference.  When I bought the bike it was only running on one cylinder so the dealer had to drill out the mixture screws and turn them out a few turns, if that makes any sense to you guys.  That definately helped alot.

Yow!  You bought this bike new?  The bike should _not_ come new with incorrect mixture.  It's possible that the dealer had it sitting for months, and got some rust into the pilots, and the adjustment simply compensated for a partially-blocked pilot jet.  By messing with the mixture screws, the dealer technically made it illegal to ride, unless the bike went through a full emissions certification afterwards, then resealed the screws.

I'll admit that many of us have tuned the mixtures, but this is not right to have done on a new '04.  

On the other hand, this means that you can play with the mixture, and the dealer can't pull a "hey, you modified it so I don't have to honor the warranty".

Yeah, the mechaninc said it was a hush hush operation.  They told me that stock the carbs run too lean (epa stuff) and also small particles may have been preventing the fuel from entering one of the cylinders.  I don't know if it does anything performance wise, all I know is it's day and night difference between using only one cyclinder to actually running on both.  

Would I still benefit from jetting or is this close enough to the same or better?   :dunno:

Quote from: BKYeah, the mechaninc said it was a hush hush operation.  They told me that stock the carbs run too lean (epa stuff) and also small particles may have been preventing the fuel from entering one of the cylinders.  I don't know if it does anything performance wise, all I know is it's day and night difference between using only one cyclinder to actually running on both.  

Would I still benefit from jetting or is this close enough to the same or better?   :dunno:

Yes you will benefit greatly from re-jetting - the advice is in the archives - do a search or:

just go one size up on the pilot to # 20, three turns out on the screws that the dealer already adjusted (that is three from lightly bottomed - and I bet that is where they are right now) one size up on the mid-speed jet, one size up on the main .  If you change to a K&N in the air box, one more up on the main (about 132.5 or 135).  If its pod filters you will probably end up with around a 140 main.  If its pods and exhaust then you will end up around 150.  These recommendations are borderline rich - get it too rich and it might run poorly - too lean and you start recognizing the pieces of metal coming out of the exhaust as belonging to the piston crowns.