Need help with 1992 GS500

[92gsinND]

I just bought a 92 GS500 locally.  It runs quite well and I am very pleased with the bike.  My only problem is with a stumble it has.  When coming off idle or holding a constant RPM (usually between 4k-5.5k) the bike will sometimes stumble quite badly.  I have replaced the O-rings between the head and the carb boots which helped somewhat.  I have also gone through all the vacuum lines, replacing any worn ones and even checked the diaphrams for holes or cracks.  I did not find any problems with the diaphrams but cannot rule out a pin hole or hole to small to see.  I have replaced the plugs, wires, and fuel filter to no avail.  I am a mechanic by trade, but bikes are somewhat new to me.  Does any one have any ideas or should I take it to a dealer who will charge me more than I paid for the bike .  Also, if anyone has a web link to the proper way to tune the carbs for this bike, I would appreciate it.  If it helps, they are Mikuni BSR34 carbs.  Thanks in advance

[hmmmnz]

hmmm. that is generly where the gs has its flat spot, im gathering its a us model.
a rejet is usually the answer as for some reason they made all the us models severly lean. (emmision laws mabee)
your could try adjusting the pilot air mixture screws on the bottom of the carbs as well as i beleive your will be set to 1 3/4 turns out. wind it back in and see if its correct, then wind it back out to 2 turns out.
if the carbs havn't been messed with in the past. there will be a brass cap that you will have to remeve before you can change the air/fuel mixture.
just drill a small hole in it and get a wood screw partly screw it in and pull the suckers out.
i dare say that'll make a big difference.
let us know how you get on from there

[92gsinND]

A little more info for you guys.  I have heard that exhaust changes can effect the carbs and they may need to be rejetted.  I am running a Vance and Hines SSR slip-on exhaust.  Not sure if that changes anything or not, but thought it might help to know.  Also it is a US model bike.

[Kasumi]

With a new exhaust and been a US (severly lean) i would suggest a rejet.

[hmmmnz]

when i did my exhaust i didnt need one but it wouldnt hurt just cause you'll be so lean, did you adjust the mixture screw on the bottom of the carb??

[gs400e]

A '92 model get the bs33 not the bsr34 . If you are sure for the bsr34 it's mean the carbs have been change by the previous owner .

[commuterdude]

Are you running the original fuel petcock on the frame?  There is a diaphragm inside that can leak and cause fueling issues. 

[Paulcet]

Check the date on the OP Commuterdude

[gregvhen]

try putin a size 4 washer on the needles to raise them up 1 mm i think it was. buddha knows what washer im talkin about, PM him. he a moderator so his name should be at the top. hes very good with carbs and many people on here have him do their rejets, and ask him about carbs.

[sledge]

After almost  3.5 years I would guess the OP has bottomed it by now 

[commuterdude]

Far out!