I am new to your group but I have a GS500 I want to rejet for more power as I am racing it in California.  Do you get more performance if you rejet per the rejetting article on your site?  I don't know how to contact the author.  Anybody tried it?  What else can I do for a performance increase.  I want to give the ex500's a run for their money.

Any help would be appreciated.   thanks in advance.

Dennis

There is a matrix somewhere... and pablo has the How to on his site.. both should actually be the same thing... Unless you have a 01+... then search for articles pertaining to that.
Cool.
Srinath.

Where are in California are you?  Are you road-racing the GS?  

I have 150 mains, K&N pod filters and V&H exhaust and the bike seems to run okay.  However, most racers that I've talked to have told me that they got more power with smaller mains, especially after doing head work.  I haven't noticed any hestitation or bogging though. Wiith two washers on the needles, I don't have any flat spots either.

Adam

With a jet kit smaller mains work fine cos the kit needles are a radically thinner profile especially the bottom 1/2 inch. With stock needles 150's work best. Head work etc change the flow characterstics... so no idea what jetting will work best. That is for the pre 01 bike though. And 40 pilots.
Cool.
Srinath.

I am racing the bike at Willow Springs in California.  This is a very fast track so I need top end and also some power to get out of the turns.  I have only had it out one time (last month) and couldn't get the top end.  I was only able to get 105 tops on the straight with standard gearing @ 9000 rpm so I just put one tooth smaller sprocket on the front so I can get drive out of the corners and also wind it up higher for more top end on the straight.  any suggestions will be appreciated.  thanks     Dennis

Was there any talk last month about the proposed WSMC GS-spec series?  If I can swing the cost, I may participate next season.

Even with substantial modifications though, I don't think the GS will have the horsepower to compete with the EX500s and FZR400s at Willow.  Although in the one race I watched at Willow last spring,  did see an expert on a GS beat novices on FZR400s.


Adam

welcome.
look up JeffD's rejetting and I have some info on my site as well. Look in for sale forum for KevinC's racing bike he's parting out-lots of great parts there.

that smaller front sprocket wont get you more top speed. You should be able to get higher than 9k rpm on your stocker. I've seen 125mph @10,500rpm and another rider here has been consistently at 130. Both stock bikes, mine an 01, his an earlier model.

I also want to rejett my carbs on my 2002 model but the articles all pertain to older models and I know that 2001+ plus models require a different jet kit. Why is this? Are the pilot and main jets different sizes than previous years. It's a US bike. I only really want to rejett for warm up reasons not really power. I assume all I really need to do is change the pilot jetts to 40 to accomplish this right? thanks in advance.
lou

Yes, there has been talk about a special GS500 class but nothing yet from the guys at WSMC.   the reason I want to re-gear with the smaller front sprocket is that I can get 11,000 rpm in 1 thru 4 gear but the bike doesn't have enough poop to maintain that rpm in the higher gears.  :dunno:  Maybe it is wind resistance.  That is why I am regearing it.  suggestions?     thanks

I am running 140 mains now. Tried 145 but they where too big, no top end. Current gearing is 14/40. Should of had 14/39 at Jennings GP, needed more top speed but had plenty of drive. Easily maintain 10k. Stock engine (for now) except for: full yoshi, k&n, ignition adv.

Quote from: gs2svI also want to rejett my carbs on my 2002 model but the articles all pertain to older models and I know that 2001+ plus models require a different jet kit. Why is this? Are the pilot and main jets different sizes than previous years. It's a US bike. I only really want to rejett for warm up reasons not really power. I assume all I really need to do is change the pilot jetts to 40 to accomplish this right? thanks in advance.
lou

2001 and up carbs are much different - there is a jetting matrix on the board that talks about how to re-jet.  The pilot jet is a bleed type and stock is 17.5.  Going to a 20 is about the same effect on the 2001 and up as going to a 40 non-bleed type on the 2000 and earlier.  This should be done no matter what else you do, or do not do, to the bike.

There is a third jet (for midrange) that some have indicated could go up in size.  I do not remember the stock size off hand - but your dealer can take a look at the parts manual and tell you.  If everything is stock, going up one size should have a similar effect to raising the needle by moving the clip (non-US models only) down one notch or putting a washer under the clip (US models) and should help the lean spot bog that exists on the standard jetting.  It may need more than a one size increase if you have modified the intake by adding a pod filter or the exhaust has been replaced.  My experience was that changing to pod filters had a much bigger effect on jetting than the addition of a slip-on muffler.

The main jet is 127.5 (I think) stock.  I went up two sizes when I had the stock air filter and it was better than stock.  Then I went to K&N individual filters and it ran well with 142.5 mains and with 145 mains.  I went to a slip-on and went up to 150 mains.  Ran fine on 152.5 in cold weather (50 and below on the F scale) and got a bit rich in very hot weather (90 plus) - 150 seems to be alright in warm and cold.

Darryl, are your carbs jetted with OEM jets/needles or do you have a Dyno jet kit installed?

I'm just curious because I have 150 mains and have opened the bike to about 100mph (indicated) with no problems and a good bit of power to spare.

Adam

One thing I have noticed about jetting is that there are different jet requirements for each type of riding even with having the same modifications. Most street riders seem to choose a larger main while most racers seem to select a smaller main. On the track I stay in the 8-11k range and rarely drop below 7k unless I miss a down shift into a turn. On the street, riders use more of the mid to lower part of the rpm range while only hitting 10k only occasionally. Choose your jetting for your bike and riding requirement. Also, don't forget that elevation, temperature, air density & humidity all play a role in carb tuning, more so in a 2-stroke than in a 4-stroke (I used to tune a 2-stroke race bike which is one of the reasons I have a 4-stroke).  What others post is a good starting point but may not be ideal for you.

Quote from: Adam RDarryl, are your carbs jetted with OEM jets/needles or do you have a Dyno jet kit installed?

I'm just curious because I have 150 mains and have opened the bike to about 100mph (indicated) with no problems and a good bit of power to spare.

Adam

When you were at 100mph, were you at WOT?

It has oem jets & needles. I stay with Mikuni jets, just more experience with them. I don't have any idea of my speed (tach only). The flatness was noticed at WOT in the upper gears. One thing I forgot to mention was that I did find one of the carb tops was cracked when I was changing to smaller mains. Not really sure how that would affect the flatness I was experiencing. But is was fixed when I put the 140's in. Next time on the track, I am going to try to keep stepping up a size until I hit the flat spot again to see if the cracked cap was causing a problem.