Sportbike Racing Forum banner

-1 on front sprocket vs. top end

2343 Views 18 Replies 14 Participants Last post by  ZX-Tex
I have been toying with the idea to dropping a tooth on my front sprocket for a little extra torque. My question is, will my top speed suffer considerably?

Thanks for the info! /images/icons/smile.gif

See less See more
1 - 19 of 19 Posts
In theory, the top speed of my 9R is 172mph. After going down 1T on the front, I can get to about 165mph (by GPS, the speedo reads about 185 at that speed). That was bouncing off the rev limiter in 6th..

Meddle not in the affairs of Dragons, for you are crunchy and good with ketchup
it would be very close to a percentage, calculated like this:

I think your stock front sprocket is 15T. Going to 14T represents a change of about 6.66% (100/15)

If your top speed was 155mph, then 6.66% off of that is 10.3mph. New top speed = about 145mph.

"<font color=blue>How about never, is never good for you??</font color=blue>"
Blue dragon is right. I dropped -1T last week and it made a big difference in acceleration. Your top end will not suffer that much. it will only take about 20min to do the job right as well. just remember to use a 1-1/4 6point socket. I tried metric and it fits too loose. you will also need an impact gun. manually sucks like H-E-L-L. loosen rear tire and slide it all the way forward so you can get the chain off rear sprocket then you can get chain off the front easier. good luck

Oh yeh if anyone is interested you can get a Hanes Kawasaki motorcycle manual Hardcover book for only $17.89 + $5 shipping from they have excellent service. I ordered mine last thursday and it got to me on sat. only took 1 day to get to me.
Theoretically yes...but real world you will not lose any speed on the top end
With the stock sprocket and you atop your bike ..The likeliness it'll even see the limiter @ 6th gear is sslim to none!
With the 14tooth(-1) it will make it to redline and compensate for wind resistance through tourque multiplication! As was the case with my 9R
Thanks for all the info guys.

I guess you guys would recommend doing it then?
What will be the biggest difference by doing this?


See less See more
where in Rhode Island you from?

I'm in Westerly

See less See more
Hey All,
I have a buddy who changed his front sprocket- he brings the front end up without even thinking about it-- lightning quick, but he says the tach is screaming in 6th gear, also about 10-15 mph slower ( from what he says)> he did it for quickness not top end though< he likes it.....

hope this helps


See less See more
I just replaced my sprocket over the weekend and the difference was huge for me. I have a much better idea of when my rear tire starts to heat up and stick now. At highway speed (about 70) my rpm gauge shows about 500 higher than normal(from 4000 to 4500) which is fine by me because I dont think I've ever met my rev limiter. I did opt to use a air ratchet on my bike and it was alot easier but a friend of mine put a bar through the spokes on his rear tire to keep it from moveing and it still took alot of muscle to break it loose.

See less See more
I've been considering this move for awhile myself, i previously replaced my chain and sprockets at 8000 miles, and the shop went up one tooth in the back then, so i think the next time i get my tires changed i'm gonna go up a full three from stock on the rear, since they're gonna have the tire off anyways... my chain is plenty long enough, so no worries there. We'll see what happens here in a couple of weeks...

See less See more
thanks for all the input fella's /images/icons/smile.gif

See less See more
As mentioned above, you can expect 1000 rpm off the top or 500 in the middle. 1 tooth up front equals 3 in the rear and it's a LOT cheaper so if you don't like the results you're not out so much. You'll like it though! First gear on Kawi's tends to be quite tall so -1 up front brings city riding into the normal range.

- Not everybody has what it takes to be a <font color=green>Kaw</font color=green><font color=purple>Boy</font color=purple> -
yeah i like it alot better now w/ the -1 vortex in the front. it only took like 20 min. to change, the sprocket was like $25 and WOW what a difference. i say just do it you wont be disappointed.

Oops...sorry officer I thought I was going 45. The bug on my shield must have covered the 1.
thanks again, I think I'm sold!

See less See more
The post was in reference to a 6R originally, but I saw a few 9R guys chime in as well, so hopefully I'm not completely out of line. I too had been thinking of dropping a tooth in front, though in retrospect I'm not sure why. It made sense that the top end would change little since the bike could rev more freely, and closer gearing on the bottom end would allow better control, gear selection, whatever. The sprocket arrived last night and the change out was, as assumed, a 10-15 minute affair (with air tools, figure a LOT longer than that without).

This morning's weather being nice and my curiosity as to what this new gizmo would do for the bike being high, I decided to ride to work today. My ride is around 70 miles, 80% of it canyons with a few fast sweepers and straights (some of the same roads I assume the pacific group takes when riding to Ojai). The verdict….I hate it.

My 9R feels like a 6R, no offense to the 6R folks out there. Rev's pick up quick in the corners, but to maintain any speed the 9's hallmark torque grunt has been replaced by more shifting and reving. On sweeper roads where I typically cruise 90 to a buck ten in 4th thru 6'th, I was stuck in 6'th and not a cruising 6'th either, a decidedly revy 6'th. Very annoying. I was able to run it up on one straight and recorded 165.2 on a very accurate digital speedo…pinned to the throttle stop, though I've no idea what the rpm was, 11+ I assume. The upper end speed is fine with me, I have no interest in breaking Mach, but I'm frankly surprised at how different the bike feels on the whole.

I can see this being a good mod for a 6R, as it would bring additional gearing torque to an engine that could use it down low (and which revs higher to cover the upper end). I was really looking forward to the performance change this modification promised, but now I can't wait to get it off. Guess it's true that you don't know what's best til you "improve" what you already have. Just thought I'd post this as a counterpoint to some of what I've read. I'll gladly back it up…any LA area 9R guy who wants to try out a front 15 is welcome to this one, gratis…well, cost ya a beer or 2.
See less See more
My 12 is 46/18 stock. I am going to change both the front and the rear sprockets to make it 47/17. That should maintain wheelbase, but I am concerned that the chain might be wrapped a little too tightly around the front sprocket....

Its also time for a tyre change, and I thinking of dropping down from a 200 in the rear all the way to a 180.

Life is precious. Treasure it.
Thanks for all the input fella's.
Appreciate it!

See less See more
i just went up 2 in the back on my 6r. i love it. best mod so far and only 40 bucks.

See less See more
-1 up front is a great mod, I did it on my 9R.

And, as for top speed loss, so what if you lose 4-5 mph? How often do you really need to go 165 mph instead of 170 mph on the street anyway?

Einstein says high speed slows time, so go fast, stay young!
1 - 19 of 19 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.