This is my first year riding and I just finished fixing up my gsf. So I decided Im going to do some small upgrades to my 04F and my first mod I wanna do is change the front sprocket to a 15t. So my question is can I just slap on any 15t sprocket on or do I have to buy a specific one? Do I also need to but a different chain?

PS,
Still a noob at this!!!

You can go to any website and enter in your Model and make and theyll show you the sprocket that will fit.  You don't need a new chain for a 15t front sprocket, only if you get a rear sprocket with enough teeth.

http://www.denniskirk.com/jsp/product_catalog/Product.jsp?skuId=8008015&store=Main&catId=415&productId=p80080&leafCatId=41508

this is the front sprocket you want.

True, he doesn't NEED a new chain, but it's likely a better "upgrade" than a sprocket. 

Put a smaller sprocket on an older chain, even 1 tooth smaller, and you're getting pretty close to the maximum adjustment. 
The inch or two of tolerance in the adjustment screws - the stock chain uses ALL of that. 
And, I'm betting, being new, he bought a used bike with an older chain.  No offense, I did the same thing. 

Thats what I did when I got the bike but replaced it immediately before I started riding it this season. I was also wondering if swapping out the rear shock from stock to a katana 600 would be a better mod??

Yes.

Just don't shift into 6th gear, or maybe even 5th for a month. If you like it, change your sprocket. If it drives you nuts, don't bother.

I ordered the 15T from Dennis Kirk as my first mod/upgrade.

Still one of the best things I have done.

Quote from: O.C.D. on May 28, 2010, 10:07:39 AM
I ordered the 15T from Dennis Kirk as my first mod/upgrade.

Still one of the best things I have done.

agreed, best bang for your buck.

Quote from: drduimstra on May 27, 2010, 09:52:49 PM
So my question is can I just slap on any 15t sprocket on or do I have to buy a specific one? !

Depends what you term as specific.....Not every sprocket is the same, it may sound obvious but you need one that is designed to fit the GS500F

We changed out the stock 16tooth front sprocket for an 18tooth AFAM. A little hard to find, but makes the bike a lot nicer to ride - you can hold the bike in any gear longer, revs at freeway/highway speeds are now at a level where the bike gets better gas mileage and less vibration through the bars.

Thought it might make the bike's acceleration a little lethargic but it's barely noticeable - you just hold it in gear and let it wind up. Top speed still right around 180-190 km/hr indicated; fast enough for a court appearance 

Quote from: SAFE-T on May 28, 2010, 09:57:41 AMJust don't shift into 6th gear, or maybe even 5th for a month. If you like it, change your sprocket. If it drives you nuts, don't bother.

Why would anyone ever do that?  If you're trying to say that the GS will only go 60mph with a 15t, you're wrong.  It'll still do the same 115-120mph (indicated) it does with a 16t, you just have to shift a bit more under 40.


I have a 15T front as well.  If you're not a 20 mile+ commuter, do it. 

I also have a Kat600 rear shock.  If you weigh more than 120 lbs or ride with a passenger, do it.  There are some other models that fit too.

Do the front springs too.   I went with progressives, 'cause I ride in the rain on rather rough streets.  You can go with straight-rate springs if you want.  When you pull the worthless front springs and giant spacer out of your forks, you will understand...

Mine will redline in 6th with the 15t at 129mph, I did it Sunday for the 10th+ time.  I am thinking of getting a 140-70-17 tire which will increase the gearing by ~2.3% to get it over 130.

With a 15t on a stock bike it will probably go 118ish at ~10000rpm

I'm pretty sure it's just over 9k at 120 (indicated) with a 15T.  My GS won't do it any more...  Only just under 110mph these days.

at 10100rpm my bike with stock rear sprocket, 15t front sprocket, and stock size tires is exactly 120mph. I know this because thats as fast as she will go with me sitting up-right with my book-bag on. That dang bag is like a parachute.

my bike is all stock and it barely goes over 95mph on 5th gear

Once I fix my tach, I'll have to collect some data.   

Quote from: A Non eMouse on July 29, 2010, 10:36:38 PM

Quote from: SAFE-T on May 28, 2010, 09:57:41 AMJust don't shift into 6th gear, or maybe even 5th for a month. If you like it, change your sprocket. If it drives you nuts, don't bother.

Why would anyone ever do that?  If you're trying to say that the GS will only go 60mph with a 15t, you're wrong.  It'll still do the same 115-120mph (indicated) it does with a 16t, you just have to shift a bit more under 40.

The point is to find out if your riding style works with the different gearing.

I had a different rear sprocket on my VFR800 for two years which was a similar change to going to a 15tooth front sprocket on the GS500. Roll-on performance was better, but riding at 7000 rpm on the open road got a little tiring and you can get the same "roll-on" performance by simply staying in a lower gear to begin with. I did a number of 5th/6th gear roll-on comparisons between my VFR and others of the same year and it was exactly like being one gear down > their 2nd was my 3rd, their 3rd my 4th, and so on.

And yup, the '07 GS500 we have still goes 115-120mph (indicated) with the 18tooth sprocket but now gets better gas mileage and only turns 4500 rpm at 65 mph and 5000 rpm at 75mph. 

So whats the biggest difference from getting a smaller sprocket and a bigger sprocket? I would just like to improve my speed and maybe even get better gas mileage

Stock is 16T. Less teeth will give you quicker acceleration and worse MPG, more teeth will do the opposite.

The smaller front sprocket increases your rpm in each gear for any given speed, such that you get into an rpm range that makes more hp and torque faster.

So the smaller sprocket will help your GS accelerate quicker, but in my mind it makes an already pretty useless 1st gear even more useless, and 2nd gear more like the useless 1st gear used to be.

With the 18tooth front sprocket the GS500 now has the same gearing as an SV650. Which is what I would buy if I was serious about 'improving my speed' ~ the GS is remarkably good considering its genetics, but it's still fairly agricultural in feel and about 20hp shy of being really interesting.   

In my experience with my VFR, the gearing change didn't really affect the gas mileage enough to worry about - maybe only 2 mpg.

On the GS500, the 18tooth sprocket gave us around 68 mpg in twisty mountain riding. Another GSTwins forum member reported getting 75 mpg on their daily commute with the same sprocket, so we're in the ballpark.