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Upgrades /
RejettingIntroThis page contains sections on "how", "why", and also "to what settings". You should probably read ALL of the sections before even picking up a tool. HowThis is a good pictorial how to: Poor Man's Rejetting Pictorial There is also, of course, the canonical site: http://www.gstwin.com/rejet.htm VERY detailed video of the process is at http://www.youtube.com/watch?v=AJh1hxNf7BA It is for "jet cleaning", not replacement, but it's basically identical, right down to removal of the jets. Just skip the cleaning part! While taking the carbs apart in all this, if you have the original soft, brass, JIS type screws, you may want to replace them with easier ones, as mentioned at Maintenance.FreeSeizedCarbScrews A good place to order jets online seems to be http://www.sudco.com/mikunijets.html. For Pre-2001 models your mains will be N100.604 and your pilots will be N151.067. For 2001+ models, your mains will be N102.221 and your pilots will be N224.103 or VM28/486. Although they have a website you must still call them to order. The phone number is (323)728-5407. However they only cater to a minimum quantity of 4 per jet. Some of the sub measurements may be hard to find: for example, 62.5 rather than 60 or 65. Currently, one place that still sells the full range is Jets R US WhyThe GS500, GS500E and GS500F are known to be jetted on the 'lean' side to improve fuel consumption and exhaust emissions. This is not optimal for best performance (ie. acceleration, power, torque, faster warm-ups, engine cooling and engine efficiency). A lean engine is one whose combustion has more air than the perfect air/fuel ratio. In 2001 the GS500 carburetors changed to a new design that features three jets. The stock jets for the GS500 are: There are four things to adjust your air fuel mixture. The pilot jet and idle screw affect the mixture at idle. Adding washers to the needle jet affects the mixture at partial throttle. The main jet affects the mixture at or near full throttle. Larger jets, or more washers on the needle jet, will make your bike run richer within the corresponding throttle range. 2001 - 2007 CarburetorsThe advantage of these newer carbs are the inclusion of a Mid Main Jet that allows finer tuning of the fuel to air ratio of different throttle openings. YEAR + Jet Size These bikes use Mikuni Carburetors / Jets with the following part numbers for their jets: To what degreeA conservative Starting Point for upgraded Jetting (Pilots/Mid Main/Main) for a: Unfortunately Re-Jetting is a black art (so many variables including humidity, altitude, engine condition etc etc) so often much tweaking of jet sizes is needed to find the perfect combination. See the Matrix for what other users have found to work. You can also see the matrix with easy data entry at http://beergarage.com/GSMatrix.aspx A thread here also lists members Jetting and Upgrade information http://gstwins.com/gsboard/index.php?topic=35237
Same info in original table format. 89-00
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Air Filter: (s) - Stock Air Box, (p) - Pod replacement for Stock Air Box (lb) lunchbox Note: r- rich, sr - slightly rich, p - perfect, l - lean, sl - slightly lean -Courtesy of Mike |
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