Suzuki Shop says NO to rejet

[Size_Twelve]

Hey guys, I went into my Suzuki dealership's parts department today looking for a new set of jets for my carb. Based on the feedback from this forum I came up with some numbers (132.5, 62.5, 27.5) for the different sizes I needed. When I went into the parts shop though, the guys told me rejetting was a bad idea.

One guy in particular said that his partner "lives" the industry and has seen hundreds of dynonometer runs on all types of Suzuki's, including my '05. He said, that in all of his runs he's never seen a single one come lean from the factory. He said in fact, that if anything, they all come a little rich to protect themselves from different elevations.

Their advice was to simply let it be. They both said that rejetting would add very little, or nothing noticible performance wise, and could very well cause the spark plug to foul out.. As a matter of fact, the one guy said that if I increased the size of the mains anymore, he'd almost guarantee it. I asked about possibly adding in a new K&N air filter, and again they said it might make some little difference, but unlikely not much at all for the $50 it cost to get it.

Now the clincher is this. They said that if I wanted the stuff, they'd go ahead and get it as they had it in stock, but it was their advice not to do the rejet and just save the money. A parts dealership telling me to save my money??  Because of this, I tended to believe them, and wondered if anyone here had any opinions on this.

[blue05twin]

Added the K & N luchbox filter, and a wileyco exhaust did rejet and I noticed a difference for the good.  btw you can get the jets from www.sudco.com they would be cheaper and I think it's USdisel.com that thas the K & N luchbox for real cheap.  Then again maybe it was my imagination that it seemed better 

[badkarma506]

k&N jets and a exaust you can get up to 12 hp or so abot a 25% increase in power over stock.   if they came rich from the factory, "to protect themselves" and you rode to a higher elevation whare the air was thinner, then they whould be way rich due to the decreased O2 available in the atsmophere, and whould foul plugs.  your dealer is full of asshats, and they just didn''t want to deal with you, because you have a  gs and not a gixxer, is what it comes down to.  either go find a new dealer or order online and do it yourself. it's not hard, it's all bolt ons with simple hand tools that you can do in a afternoon in a parking lot. so don';t worry about it.  and find a new dealer.

[pantablo]

i agree with davipu, er karma. its well known and an established peice of knowledge that the bikes are set up to run lean at certain rpms-specifically at certain rpms-the rpms that the bikes are tested for emissions at. magazines talk about this all the time. and there are boatloads of people on this forum alone that know first hand how much rejetting helps.

[Wrecent_Wryder]

h6

[Gisser]

+1

Rejetting mine made a huge difference, night and day, not something you could just imagine away. It's just flat-out a much better ride now. The original jetting is apparently what happens when engineering decisions are being made by politicians. In retrospect, I consider the uneven, constantly wavering throttle that the factory jetting caused to be borderline unsafe.

IMHO, the only real question is whether they're trying to decieve themselves and you, or just you.

The dealership was essentially correct.  They were telling the OP that no power gains would show up on the dyno after rejetting.  It's true that one can improve throttle response and rideability with minor carb tweaks although the '05 model may have already addressed these issues to some extent with the addition of the mid-main jet.   

[Gisser]

The most optimistic gains one can hope for can be found on the GSTwin.com dyno run:  http://www.gstwin.com/dyno_run.htm

This is not simply rejetting.

With a drop-in filter, a V&H pipe, and Dynojet kit, this set-up yielded 43.2 HP on the dyno.  Most sources have the stock GS500 at about 39.5 RWHP, so if we presume that the 43.2 HP figure for the piped & jetted GS500 is relative and accurate, there is a gain of < 4 HP--or about 9% which may be worthwhile if you can get away with riding around town with a racing pipe (louder than you might think). 

However, I did say optimistic because there was no stock run on this dyno with which to make a comparison--results can vary from dyno to dyno--and I've definitely seen lesser numbers posted from similarly modified GS500's.  And the recorded gain is peak power; the powerband may well show losses at lower RPM's.

[Wrecent_Wryder]

[g

[domas]

All UK 2001+ models come with 115 mains because of strong european emmision control. My dealer also says dont mess with the carbs, because he just lacks knowlegde about it. If it wasn't for gstwins.com i would still be afraid of changing anything on the bike, and thanks to all gurus here i am doing everything myself, even messing with the carbs. The first time i opened them i felt like i was doing it 10th time.

So trust the guys here more than your dealer or some car mechanic.

[TheGoodGuy]

im going to be playing with my jets tomorrow.

I am running 20, 62.5 and 145's i believe.. but its still lean on the top end... with teh K&N.. i can feel it bog down a bit at 80mph.. so i am going to shim the needles tomorrow and see how it does.

[Firegod42]

Greetings all,
               New 05 500f owner here. Had the bike about a month and really like it. Alot better than the Rebel 250's we rode in the safety class.
Anywho; As I was saying, It's an 05 with about 200 miles on it and I must say that it runs really rich all the time. It loads up bad while idleing and stutters on take off. On deceleration (engine breaking) it will sputter and backfire a bit. My dealer suggested to try the K&N to lean it out before messing with the carbs. Any thoughts out there on this?
If rejetting and K&N will cure the throttle jerks and the rich running issues which seems to be what all are saying then this is what I need to do. Right?

[FearedGS500]

i like my bike just the way it is . i'm just waiting to get the money so i can get my jarden exaust ,k&N and rejet ( i go to the local mom and pop cycle shop   i like to sport them better then the stealers ) i know the owns son pretty well . we go riding all the time ( he has a 94 CBR 900RR  ) he was telling me the same thing rejet . with the power to weight ratio  just about any hp gain is noticable and will make the bike feel like a new beast

[un1261]

I rejetted my 05 F a couple of months ago, and well I'm very pleased with the outcome.
I also added a K&N lunchbox filter. It went from a tame little motorbike to one that has a slightly larger stones. 
It has better top end and is quicker to throttle up then ever before.
I do not who told not to waste your money but it's your bike, do what you want to make it better then factory stock.
By the way the new K&N lets you hear the motor, sounds like an engine not a sewing machine.

[corndog67]

Greetings all,
               New 05 500f owner here. Had the bike about a month and really like it. Alot better than the Rebel 250's we rode in the safety class.
Anywho; As I was saying, It's an 05 with about 200 miles on it and I must say that it runs really rich all the time. It loads up bad while idleing and stutters on take off. On deceleration (engine breaking) it will sputter and backfire a bit. My dealer suggested to try the K&N to lean it out before messing with the carbs. Any thoughts out there on this?
If rejetting and K&N will cure the throttle jerks and the rich running issues which seems to be what all are saying then this is what I need to do. Right?

A brand new bike (200 miles), should not be loading up. The jerky throttle is most likely a lean condition.   If it is loading up after it warms up and with the choke off, I would take it back to where you bought it.  Something is not right.  New bikes are never, ever, rich, right from the factory.  Emissions laws won't allow. it.

[KYGS500E]

ok... size 12... where di you get those numbers for a rejet? thats not quite what I would recommend.

BYpass the stealers... they DO come lean from the factory and that is all there is to it...

You can find the K&N's online for 30 bucks... if you order from a mom and pops shop or just go to the service dept. at yoru local stealer adn ask for 127.5-132 main jets for a mikuni carb and 40 pilots (no bigger... if at alll just one step up)  It should cost all of 10-15 bucks.  If you order online you'll pay shipping.  Go to lowes and buy some #4 washers and install it on your own.  Its really easy and If you want I'll talk you through it via phone.... i'm sure there are some gs'ers here that live near you... where are you at? 

Plus... those sized are way off if you're wanting a stock bike... (ie no filter or pipe.)  PM me if you want specific ?'s answereed

[Size_Twelve]

I got those numbers from this reply by Roadstergal about rejetting the '04+ models. I made a mistake on the OP. It was 22.5 pilots (one step up) not 27.5. I basically took all three jets and went one step up on them, as I will be adding a new air box at the same tme.

Anyways, I've already had the carbs apart, and removed the stock jets, as I brought them into the dealership with me. I do appreciate the offer for a walkthrough though    that was cool of you. From what I'm reading here though, it sounds like people ARE noticing a smoother powerband with the new jets. So regardless of what the dyno guy says, I think I'm going to go ahead and rejet.

I don't know of any Mom & Pop places around here that do any bike business, so I guess that leaves an online wholesaler. I'm from Michigan btw, Lansing area. Home of the broken asphalt, tar snakes, and 100 mile straightaways. 

[hmmmnz]

good on ya, stuff those gits, glamourised parts changers 

[werase643]

k&N jets and a exaust you can get up to 12 hp or so abot a 25% increase in power over stock

I want to see that improvement, drunk karma....3-5 HP max about 10 % in real world


hi dave

[badkarma506]

add a comma and a period in there.

a exaust you can get up to 1,2 hp or so abot a 2.5% increase

[aplitz]

k&N jets and a exaust you can get up to 12 hp or so abot a 25% increase in power over stock.   

I've got dyno sheets that say otherwise, 50 horses at the wheel is a huge improvement.  My '01 with individual pods, Jardine full exhaust, V&H advancer, and two hours on the dyno netted 45 at the wheel (albeit at 4500ft elevation).  The next 5 horsepower are going to be tougher and moer expensive to get.