Has anyone tried a 40 tooth rear sprocket?

[gahmp]

Hello all,
I've had a GZ250 for almost a year now. I love it. It does everything I need it to do. I would however like to take it down the highway at 65-70 MPH without feeling like I'm killing my sweet machine. I have read many posts in which the front sprocket was changed from the stock 15 tooth to a 16 tooth. This would take the gear ratio from 2.733 to 2.5625. I have read a lot of complaints that after the switch the top end speed goes south. If I were to change the rear sprocket from the stock 41 tooth to a 40 tooth it would give me a gear ratio of 2.666. That would fall pretty much in the middle of the differential between a 15 and 16 tooth front sprocket. I'm thinking that the one tooth off the rear sprocket will be enough to keep the bike in it's power band therefore allowing maybe a little extra power at highway speeds while simultaneously reducing the rpm's its kicking out and all the while improving the MPG's. (I know I'm a dreamer) If anyone has tried this mod please share your results.

[Easy Rider]

Originally Posted by gahmp

in it's power band therefore allowing maybe a little extra power at highway speeds while simultaneously reducing the rpm's its kicking out and all the while improving the MPG's. (I know I'm a dreamer) If anyone has tried this mod please share your results.

Welcome!

You didn't tell us where you are......and the riding geography has a good bit to do with it .......and this doesn't answer your question.....BUT:

65-70 is still doable on the flat without a significant headwind with a 16T sprocket, but it takes a while to achieve 70 and you can't maintain that over anything but the slightest hill. It does, however, allow you to maintain 60-65 under adverse conditions (headwind or uphill) in 4th for short stretches. This is my experience with a 180 lb. rider and a large windshield.

I suspect the answer to your question is: NO. Changing the front is so quick and easy I doubt anybody has gone the other route. Is there a reason that you don't want to try that first ??

[Dupo]

A rear sprocket change wouldn't kill anyone. I'd say if you can get one and put it in .... more power to you. No pun intended.

[dan_]

So knowing that i'm completely ignorant to the subject what would happen if you had a 16 tooth front and 40 tooth rear.

[Water Warrior 2]

Originally Posted by dan_

So knowing that i'm completely ignorant to the subject what would happen if you had a 16 tooth front and 40 tooth rear.

You would want to be going downhill a lot and rarely use 5th gear except under ideal conditions. A 40 tooth rear sprocket might be just the thing. Pulling off the rear wheel is easy. Try it and let us know how it works.

[OC Hoosier]

A 40 tooth rear sprocket might be just the thing. Pulling off the rear wheel is easy. Try it and let us know how it works.

+1!

[Easy Rider]

Originally Posted by Water Warrior

Pulling off the rear wheel is easy.

Yeah, and Bob tells us that changing your own tires is easy too !!! :biggrin:

One man's food is another's poison. :skull:

[gahmp]

Thanks for the responses. Looks like I may get to be the first to try this one. I found the 40 tooth rear sprocket at http://www.sprocketspecialists.com/ for $53. The item # is 461-40. Their website lists it as being for a 1999 - 2004. I called them today and they said that it will work on current GZ's. My father has been a mechanic for better than 45 years which in my case means that I realize what it means to be a mechanic and that I am not one. It always ends up with excessive cussing and broken stuff. I am fortunate enough to have friends that are good at turning wrenches on bikes. I'm in Northern Indiana so it will be a little while before the weather will allow any significant riding. When I have this mod done I'll let you guys know the results. Does anyone know how to calculate the rpm's it'll be kicking out with the 40 tooth rear sprocket at 70 mph? I don't want to run on here but, I have felt the joy of the seat on long rides like many others on this post. The aftermarket seat choices are slim and expensive. Has anyone taken their seat to a furniture upholstery place to have stiffer foam put in it and re-upholstered?

[Easy Rider]

Originally Posted by gahmp

I'm in Northern Indiana so it will be a little while before the weather will allow any significant riding.

Boy have I got a deal for you!!

If you can wait until (late) spring, I'll give let you ride a 16T to gauge the difference.....before (or after) you go to all the trouble of changing the rear. I'm in Central Illinois and, unless you are in FAR NE Indiana, we could make a good day trip out of it.
....AND.....
I have a spare seat for sale, cheap. I tried the re-upholster route and did exactly the WRONG thing to it; basically am selling it for the pan but the new cover is really nice......although totally the wrong shape for me.

What leads you to believe you need stiffer padding?
I REALLY don't think that is the problem.

P.S. Being in Indiana, I don't suppose you have many hills, so if you don't plan on doing much Interstate riding, then I can't see the point is spending twice the money and at least twice the time changing out the rear for just one tooth. I rode mine to Atlanta and back last year......and did just fine, through the mountains, but NONE on an Interstate.

[mr. softie]

Hey gahmp, about the seat "enjoyment" issue, check out my seat mod, it works for me.

http://www.gz250bike.com/forum/viewtopic.php?f=9&t=1599