16T vs 15T sprockets

[cayuse]

OK, I'm eating my words a little here, but I now have to say there is a good argument for using the stock 15T front sprocket.

I converted my bike over the winter to the 16T sprocket and I've run it now for a couple of months and for the most part I just love it.
It stretches out the lower gears very nicely so 1st is good for more than just 10 feet and 2,3, and 4 have really nice torque at speeds
that feel really comfortable. So, for motoring around town and between towns on the secondary roads it’s perfect. The only problem is 5th gear.

The GZ doesn’t have a lot of power anyway but it really is crippled with the 16T sprocket at speeds over 100kph (60mph).
I found I could achieve speeds up to about 110kph (70mph) as long as the road was flat or downhill and the wind was not against me.
I couldn’t get mine to go faster than that without a tailwind. Throw in some hilly terrain and I’m downshifting very quickly to 4th
to keep up with (most) traffic. When that happens, fuel mileage goes out the window. This season I’m hitting the open road more
often so these experiences are somewhat disappointing. I was even starting to shop for a (gasp!) bigger bike.
But then I remembered everyone here saying the top speed would probably be reduced with the taller sprocket so I thought I would give the 15T another chance.

So, to do a fair comparison, I put the 15T sprocket back on and tried my work commute a couple of times on Hwy 1, the local “freeway”.
It’s hilly, everyone’s driving at 110-120kph and there is a little wind here and there so it’s a pretty good test. I don’t normally commute
on this route because, except for the speed, it’s pretty boring. Guess what? I’m keeping up with all the traffic, and no downshifting on
the hills! I’m even passing!! Of course the downside rears its ugly head: 1st gear is very short, I’m tempted to skip it and take off in 2nd
unless I’m parked on a hill, and all the other gears seem just a little short too.

So, what am I going to do? I’m going to stay with the 15T for a couple of weeks and make another run up into the mountains to give it a real good test.
If it works out the way I think it will I will probably switch back to the 16T sprocket and reserve the 15T unit for occasional ‘road trips’ into the mountains.
The 16T option is just too nice to give up for the local riding I do 95% of the time.
I can change the sprocket and tension the chain in a ½ hour so it’s not a big deal.

[JWR]

That is exactly what I did with my 250.

The GZ just will not pull any real hills, with the 15 or 16 tooth.

With the 16, you have a lot of throttle left, but it is not going anywhere ( no torque).

There are always trade off's.

[geezer]

ive been wanting to do a thead on the 140 rear wheel myself but you just nailed it on the head here. its pointless to try. i hear going a size tire bigger is like a 15 1/2 sproket and thats bad enough i cant imagine the loss of power using an actual 16t. all i know is when this tire finally wears out im going back to a 130! shoot im temped to try and find someone willing to trade

[cayuse]

It just comes down to what you want to do. If you want to blast up and down the freeway at 70mph then stay stock. If you want to putter around town and travel the backroads going no faster than ~55-60, then you'll probably find the 16T sprocket a great upgrade.

[jonathan180iq]

You could go with a 40 tooth rear sprocket and leave the 15 up front.

That would give you a final drive gearing of 2.66 which would fall right in between the experience of riding a 15T front sprocket and a 16T front sprocket. (15T = 2.73) (16T = 2.56)

[cayuse]

I wouldn't mind trying a 40T rear sprocket. Is there such an animal?

[jonathan180iq]

Where can I purchase a new sprocket?

"The Suzuki factory part number for a 16T sprocket is 27511-37200
The JT Sprockets part number is JTF 434.16

Sprocket Specialists make both front and rear sprockets for the GZ250.
The front sprockets are available from size 10-16. Part number: 528-(number of teeth)"

The rear sprockets are available from size 28-74. Part number: 461-(number of teeth)

[advant63]

have you done the carb mods? if not try it. it will pull you with the 16t. plus i'm sure engine will live longer for it.

[geezer]

the carb mods arent gonna change the power output much. its still gonna bog in 5th gear. and as far as i know bogging an engine is very bad for it

[MadCityRider]

I've had a grea experience bumping from the 15T to the 16T. In combination with new Air Intake, Exhaust, and the 130 Main Jet, this bike has become very fun to ride, and can now safely handle traffic over 55 MPH. I would highly recommend the change, as it's simple to do, and very effective. If anyone needs one of the 130 Main Jets, let me know I got extras...

:rawk:

- MCR

[alantf]

I've got the stock 15 tooth, & I've listened to all the comments about first gear being all but useless. I've never had any problem, so today I decided to do a check. Riding normally, pulling away from stopsigns I kept an eye on the speedometer. I found that I was accelerating comfortably in first, up to 30km/hr (20mph) before I needed to change to second. In the handbook, first is shown as 2.636 (29/11) which I assaume is the same as American GZs, so I can't understand the difference. :??:

[MadCityRider]

I've got the stock 15 tooth, & I've listened to all the comments about first gear being all but useless. I've never had any problem, so today I decided to do a check. Riding normally, pulling away from stopsigns I kept an eye on the speedometer. I found that I was accelerating comfortably in first, up to 30km/hr (20mph) before I needed to change to second. In the handbook, first is shown as 2.636 (29/11) which I assaume is the same as American GZs, so I can't understand the difference. :??:

I'm not sure either, but with the 15T, I never got anywhere near that. Do you shift at a pretty high RPM?

[cayuse]

I'm check on that on my way home today. I'm running the 15T for now, but much prefer the 16T.
note: at 30kph you are doing 6100rpm on 15T
on 16T that is reduced to 5700rpm, not a big percentage but it feels significant

And Alan, it's not a problem, it's just 'better' to most people when they move up a tooth. How much do you weigh, if I may ask?

[cayuse]

OK, I paid more attention on my way home today, and when I'm accelerating from a stop 'aggressively' I'll get it up to 30kph in about 20 feet. When I'm less motivated I'll let it wind up to about 25kph. My 'aggressive' shift points are 30kph, 50kph, 65kph, and ~85kph

[Strelok]

I can't understand the need to make 1st gear more useful. It is what it is.
Doesn't make sense to gimp 5th gear for the sake of 1st. 15T for me.

:popcorn:

[cayuse]

See my 2nd post....
If you rarely hit the highway, the 16T is a definite improvement, IMHO.
This season I'm doing a lot more x-country so I actually like the stock gears.
I posted recently in the "log your rides" thread about my trips up into the mountains around here with both the 15T and 16T gears. It turns out I really like the stock gears best when riding at speed in the hills.

[Strelok]

cayuse~

I'm in Texas. You can't go anywhere without using the Highway.
And even if you're not on one people still drive like they are.

Thanks for your Post. Made me decide to forget about the 16T.

Also forget to mention I live in the "Hill Country".

:tongue:

[cayuse]

yeah, probably not for you. Not for me either right now, but it was good while I was in my city-ridin' mode.

On a side note, I drove through Tx last August and I think I saw 3 dudes on motorcycles the whole trip. It was just too damn hot to ride. That was on Hwy 10 from El Paso down to San Antonio. I'd love to ride down there but probably on something bigger than a GZ and definitely not in August!

[alantf]

And Alan, How much do you weigh, if I may ask?

Around 157 lb + riding gear (helmet, jeans, T-shirt, body warmer)

As to the "aggressive riding" question - No, I'm a pretty gentle rider. It certainly doesn't seem like I'm doing over 6000 revs before I change. :)

[Strelok]

cayuse~

You should have been down last week in Austin.
We had 50,000 Motorcyclists here for the ROT
( Republic of Texas ) Rally. It's never too
hot to ride here as long as you don't
wear a Full-Face Helmet. I like
Half-Helmets year around.

:)

[Way]

So basically to sum this up, a 16 tooth front sprocket is like converting 5th to a sort of weak overdrive, no good for more than 60 mph? At the same time, the lower gears get more torque?

I am going to use my bike for commuting to work on a back road, 60 mph top speed. I have one steep hill toward the end of the trip but other than that it's basically flat. I've been on the interstate, I am still a newbie but it didn't seem all that fun to try to do 65-70 on this bike stock gears or not. Seems like it's too light a bike for those sudden gusts of wind at those speeds.

My main concern is the fuel economy - even though 5th is weaker, will I still be able to get 60 mpg?

[blaine]

You will get as good, or better mileage because the bike revs less.You should be able to do 70 mph on the flat,no problem.
:)

[Way]

Thanks Blaine! Excellent. Sounds like this mod is made for me. :2tup:

Now that I'm getting used to riding, I find I'm doing 58-60 without even thinking about it. But with the stock sprocket it seems like 5th gear could be stretched out a little more for cruising speed. I have a fairly short steep hill to get over and I want to do that as quick as I can since it will be dark. I don't want anyone coming up behind me too fast with that tiny taillight. I've got a hard trunk I just bought that's already wired for lights, but that's another project for another time. This sprocket project will be next on the list after my HID headlight issue is taken care of.

[cayuse]

Way, the quickest way to get up that short hill is with the 15T sprocket. With the 16T sprocket top speed only goes down, especially when you ride up hills or against the wind. That mod is only good for stretching out the low gears to make them feel more comfortable. The price for that is stretching out the top gear so it's less useful. This is fine if you're riding around in town at 40mph or less, but it detracts from highway riding. Also, Blaine's point on gas mileage will only work for the lower gears, while you are in town at lower speed. At high speeds you'll be limited by the taller gearing, so when you encounter headwinds or hills you'll get worse mileage as you push the bike harder.

[Water Warrior 2]

Thanks Blaine! Excellent. Sounds like this mod is made for me. :2tup:

Now that I'm getting used to riding, I find I'm doing 58-60 without even thinking about it. But with the stock sprocket it seems like 5th gear could be stretched out a little more for cruising speed. I have a fairly short steep hill to get over and I want to do that as quick as I can since it will be dark. I don't want anyone coming up behind me too fast with that tiny taillight. I've got a hard trunk I just bought that's already wired for lights, but that's another project for another time. This sprocket project will be next on the list after my HID headlight issue is taken care of.
Want to be more visible after dark ? Wal Mart has 3M reflective tape that works great. Red on the back of the trunk, yellow on the sides and silver/white on the front of anything facing forward.

[Way]

Thanks WW! That stuff is bright, I thought it was an actual light. I'm thinking to put some on my jacket too.

[Water Warrior 2]

Thanks WW! That stuff is bright, I thought it was an actual light. I'm thinking to put some on my jacket too.
If you Goggle reflective tape you will find lots of suppliers. There is one that has a stick on tape for clothing material that you might find satisfactory. You will know if you have enough reflective tape on the back when cages turn on their low beams and back off a fair bit.
This is the Vstrom with white/silver tape on it. It works well but isn't compliant with the rules. I have the new colors to fix that when I get a round 2 it.

[Kcarvajal]

I just installed the 16T front sprocket and I think I'm sold. I will be going on a 300 mile road trip this weekend and will gladly share my findings. But if my 60+ mile ride tonight in city/highway is what it will be like, this is a keeper. I had no issues hitting highway speeds. Granted, mostly flat, but I went up a hill while in 5th and was able to maintain my speed. Even felt like I could've given it more.

:2tup:

Thanks!
Ken

[Way]

So how did this go? :popcorn:

[Kcarvajal]

Way,
Sorry for not posting after my trip. Completely forgot about it.

The road trip went extremely well. I was cruising comfortably at 65 mph but rode around 70 most of the time, even hit 80 during spots. Granted, the RPM was fairly high, but it did well. We would go pass other vehicles such as semi's etc.

The only problem I had was a sore back/butt. I would say due to my non-stock solo seat and the positioning of the handlebar. It wa a good test, as I now know my bike (in it's current modified state) is not one for extremely long rides. Good thing I didn't get it for that. Otherwise, all is well.

Thanks!

[Skunkhome]

This thread is all over the place.. we have people stating that the 16t sprocket will give them more " torque in lower gears" There is no way that can be. The stock 15 T sprocket is going deliver more torque in any gear. Some are saying it is great for high speed and others say is is great for everything but. The issue I suppose everyone is trying to solve is the relatively short 1st gear range making transition from "stop to second" a little busy. The 16 tooth sprocket would certainly smooth out the operation by streatching out the gears but if it is too tall for overdrive than I just dont see the point. I do find 1st gear to be a bit short but it is nice to have tht extra torque when starting off up hill. Some one stated that they are considering starting off in second. By accident I have attemptd that more than once and it does not work very well. I usually end up rolling off to the side and stopping to try and find first gear. I have few hills here of any concequence and the mean elevation is about 23-25 ft. I am a heavy guy, weighing in between 240 and 250lbs though I am working on getting down to 200 lbs. Now, that said, I will tell you that I have been getting around 75 mpg and have had the bike up to 70 mph before backing off the throttle. I have been driving in the city last couple of days and more agressively so my mileage has dropped off to 66 mpg on the last 160 miles. Aside from possibly having a little taller first gear I just cant see the benefit of going to a 16 t sprocket. Sounds like we could use a two speed final drive.

[cayuse]

Yes this thread IS all over the place but that's OK Skunkhome, just pay attention to MY comments! :biggrin:
OK, and WW's, too. ;)

Cheers.

[bonehead]

I have had both. I like the 15 better-FWIW.

[raul10141964]

i have
16 t
140 main jet
2.5 turns on the pilot
unrestricted air cleaner
cruse speed at 70-75mi an with good conditions 80 mi
with out the carburator mods do not go over 60 mi

[Skunkhome]

Has anyone split the difference by changing to a 39 tooth sprocket on the rear rather than going to 16 on the front. It would be about 2% lower than using the 16t front.

[Water Warrior 2]

It might work very well but be sure to price out a new rear sprocket first. It's far more cost effective to buy a new front sprocket.

[steelpix]

Just a couple good links here on how to change from 15 to 16 t. One is from our forum here with great instruction and pictures. The other link is a good video. You can always switch back to 15 T if your not happy. Not hard to do.

viewtopic.php?f=8&t=317 (http://www.gz250bike.com/forum/viewtopic.php?f=8&t=317)

http://www.youtube.com/watch?v=CkibrlgqL_A

[steelpix]

I was wondering if the speedometer will change if you go from 15 T to 16T?

I'm thinking no as it all has to do with the front wheel. Am I right?

Thx

[jonathan180iq]

Yeah, no worries on the speedo. That reading comes from the front wheel. No gearing at all and you'll still get a speedo reading.

[steelpix]

I spent time today installing the 16T sprocket. All went well except I couldn't understand why I couldn't put enough slack in the chain to get the new sprocket on. Don't make my mistake of not loosening the chain loosening nut adjuster enough. Just when you think you have them loose enough, loosen them more and it will go smooth (That was a lot of loosening words).

[Water Warrior 2]

:lol: :lol: I think we have all been there at least once or twice.

[scott103]

I have an 09 with 14xxx? miles on it, and have put at least the last 500 on with the 16t i upgraded to. I can't tell if it hurt gas mileage, because i don't pay that close of attention, just put in $9-10 within 40miles of hitting reserve, but it seems like i've been going farther. I rode the 15t on the interstate a few times, then experienced a night and day difference with the 16t. I'm comfortable at 65-70, can still hit 75+mph, with the 15t i didn't like going over 60 very often.
The biggest benefit I found is that I can cruise on 40-45mph limit streets in 4th gear without feeling like i should hop up to 5th. I may be burning a little more gas in 4th at 45, but in 5th, i had to downshift if i slowed down at all or wanted to accellerate.
I also feel that 1st gear is finally useful for parking lots, and i can use 2nd gear in residential areas, whereas it sounded like the motor was revving pretty high at 25 in 2nd with the 15t.

I weigh 170ish, and think my bike may have been jetted in the past, so that might be why i don't feel there is a loss in power-my bike is also NOT coldblooded in 40 degree weather
I give the 16t two thumbs up, but weight or jetting could be a factor.

[FLAJIM]

Bought the bike for my wife to learn on. With the 16T she using all the gears longer which will help her transfer to a larger bike down the road. For me, at 235 I can ride at 55 mph 4500 rpm and getting 68 mpg. Sorry but I just don't like taking this bike faster than 55 but that just me.

Be Safe JIM

[spldart]

I installed the 16t sprocket a while ago. I'm loving the lower rpm at freeway speed and my mileage is unchanged. 68 to 80 mpg. 70 to 75 seems to be my average. Before and after
the upgrade.
My thinking is this. As FLAJIM mentioned you now only turn 4500 rpm to do 55 mph.
This equates to one very important fact....
Lower ring speed. :tup:
Winding out a motor is bad for components and one of the important ones is your rings...
...And your valvetrain... Anywho...
We know redline is prolly 8k to 8.5k rpm but the engine can't live long at high rev.
So this mod and keeping your speed below 65mph is a great way to increase longevity
imho.

[Water Warrior 2]

If I remember correctly the British auto industry would list piston travel in there advertising and owners manual. Never thought much of it at the time but it makes sense from a reliability standpoint. Yeah, we are going back a few decades. Modern engines in cars don't seem to worry about piston travel. Better materials and oils make things last longer. Oops, should include much better research and design too.
What was once considered an exotic design such as roller cams, overhead cams and roller rocker arms were for the rich and famous willing to spend the $. These designs are very common place now for their longevity and reliability.
The GZ may suffer from an older design but it is also the reason it is a popular machine. It is much simpler and fits well with it's target market.

[spldart]

One thing between bike and car motors... Rev's
Piston ring speed peaks at half way between top and bottom stroke positions.
It is not only a matter of stroke measurement but the revolutions per.
Both rpm and stroke length are involved in calculating ring speed.

Why do I now feel sullied after that statement?