Install a 16 Tooth Front Sprocket

[bmw633]

Without a tachometer, how does one know whether the engine is redlining at WOT. This bike is for my 130 pound daughter to learn to ride. I am also considering a 16 tooth front sprocket to keep the revs down. I just tore down the engine to the cylinder because of low compression, the bike topped out at 50 mph. This is an E-Bay engine I got from Pin Worms (sp.) Motorcycle recycling. They would not even give me a partial credit because it was past 30 days since I got it. It took the shop a couple of weeks to swap motors, then the weather prevented a trip for another couple of weeks. It ran ok for about 50-75 miles, then it started losing power. By the time we got it to the shop it took another week or two for them to find out what was wrong with it. 110 psi compression.

I copied the shop manual and went to work tearing the motor down. I am taking the parts to a machine shop so they can hone/overbore the cylinder walls and new rings, and possibly an overize piston. I noticed while removing the carburetor the black plastic top had a loose screw, which caused the top to wiggle around. Could that be the cause of low power? I am also taking the head and camshaft for a valve job and to check for wear.

[jonathan180iq]

The lose carb top would definitely cause some mixture issues. Underneath that top is the needle diaphragm. If it's not sealed, you're first letting in too much air. And secondly, I don't know that they needle will operate properly, as the top is also what compresses the spring to hold the slide in place... So that's a big leak right there.

I once cracked the black plastic cover removing a stuck screw with some vice grips. Some Epoxy solved that problem once and for all. was the other screw stripped? That tends to happen when people take their carbs apart for the first time. I'll be previous owner, or an overzealous shop mechanic bunged it up and didn't take the time to fix it.

[Fawlty]

Great Howto, but I cannot open the images in the first post. Any advice would be appreciated.

[jonathan180iq]

Uh, oh.... That's a new problem.
We'll look into it.

[dhamby]

Ive had mine for 2 weeks yea 1st gear is short.but im concerned about doing this mod im a bigger guy about 235 and worried i will loose more bottom end than what its worth ??

[jonathan180iq]

Your gears actually last a little longer. 235 isn't too heavy. Make sure your tires are aired up and give it a shot. It's only a $16 investment if you hate it. But I don't think you will unless you live in a very hilly region. It makes the biggest difference in 5th gear. The lower gears become more usable, IMHO.

[dhamby]

Thanks could u post the part number and a link where i can buy it at again so i order the correct part. Thanks gonna do it like ya said if i dont like it im out 20 bucks max .

[jonathan180iq]

Pretty sure all of that information is back on the first page. If not there, it's the second.

Lots of places should carry it.

bikebandit.com was the big one at one time

[anruari]

great how jonathan

i have my gz just 3 days,love except for onething

on long, 2-3 mileinclined i cant hold the speed much over 50, there is just nothing left inthe throttle

does this mod make it possible to keep the bike at around 60 and keep with traffic flow on the long inclines?


thanks

[JWR]

A 16t will lose top end and have very little pulling power going uphill.
You must down shift to 4th if you want to keep your speed going up a hill.

[Water Warrior 2]

Long inclines are not friendly towards a GZ. As you get more used to the bike and learn it's capabilities you may have your doubts about the lack of power in certain circumstances. Never fear, it will do everything a bigger bike will do but at a slower pace and at a lower cost. Just don't ask a GZ to do more than it has been designed to do. These are almost a bullet proof bike with a great following and used world wide as a workhorse and family limo.

[alantf]

you may have your doubts about the lack of power in certain circumstances.

As you're in Ireland, you'll undoubtably have the European GZ (the Marauder) like mine. The European model has the carb set up richer than the American bikes (due to their emission regs). I live on a very hilly island (just a giant volcano, running down to the sea, in every direction) and I don't have the problem you mention. I've had my Marauder for more than six years, so I think that you just need to get used to the bike. Don't be afraid to be a bit "rougher" with it. You'll have to let the revs build up higher in each gear, and you may not even make it into fourth or fifth. I can usually get 30 to 40 MPH up the steepest hills in third or fourth. Don't think that just because it has a five speed box, you've got to be in fifth for evey type of road. BTW, that's with the 15 tooth, not the 16. Don't even think about the 16 tooth if you live in a hilly area. :2tup:

[jonathan180iq]

great how jonathan

i have my gz just 3 days,love except for onething

on long, 2-3 mileinclined i cant hold the speed much over 50, there is just nothing left inthe throttle

does this mod make it possible to keep the bike at around 60 and keep with traffic flow on the long inclines?


thanks

The 16T is designed to lower cruising revs on the highway. It's not really meant for long inclines. For that, your best bet would be to stick with the 15T and learn to rev the bike a bike more. I can pull North Georgia mountains in 4th, even with the 16T. You'll be fine. You have a rev limit close to 8000 rpms. Don't be afraid to use them. :)

[anruari]

thanks for he replies guys and ithink water warrior is right...

just having a few doubts about the power of the bike..i had a 250 nighthawk which seemed to have more pep to it.....was thinking i should have made the jump to a kawaski en500 or something similar

one word sticks out regards this bike....workhorse...within its limits it seems a sturdy reliable bike. i had it on the motorway the other day..that was a bit hairy, not sure yet how the engine copes at 60 mph constant for a longer period..but well the bike isnt a motorway bike i get...

it ll do for now is my verdict so far.. capable to take my test on and during my prohibited period (2 years after passing test) but i malready thinking for longer journeys i need something with just a little more power to it...not a lot more though either. just something capable of maintaining 60mph with traffic flow up these long inclines

this is the only negative i really have about the bike so far....apart from that its wonderful to rideand i actually find the seat more comfortable than many members on here need to..i get a pain in my upper back long before my bum gets numb.....i added a windshield today so hopefully this will alleviate this back problem

[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

mode air filter ( do not mode the filter without change the main jet )
http://s18.postimg.org/sneq60k8n/IMG_20 ... 110644.jpg (http://s18.postimg.org/sneq60k8n/IMG_20120830_110644.jpg)

check this post to
viewtopic.php?f=7&t=6170 (http://www.gz250bike.com/forum/viewtopic.php?f=7&t=6170)

[jonathan180iq]

Really, don't be afraid to use the rev range. 65mph in 4th is fine for the bike. I wouldn't do it all day long every single day... that's what 5th is for. But when you just have to get up over that next hill, then just drop it down a gear and stretch her out. She can handle it.

[anruari]

jesus it barely gets up to 70 in fifth, but i only have the bike a week so i dont know its intricacies yet

the bike doesn t feel comfortable at seventy either....or maybe im not used to running it at 70...not sure which

my old nighthawk 250 got past the 70 mark with a lot less effort and it topped out at seventy six

the gz maxes at 72 thus far

[jonathan180iq]

The Nighthawk is a 2 cylinder, so it should spool up faster and it makes more HP by comparison too to being with. The Nighthawk would be a great bike, if the brakes were worth a crap.

The GZ will top out anywhere between 72-83MPH more or less.

5th gear on these things is basically just an overdrive. It's a very tall final drive, considering what our power output is. This is why the 16T conversion further lowers revs so much and feels like it limits overall top-end power. If we have shorter final drive gears, for example, and maybe 6 speeds instead, the bike would probably do 90+ But that's what this bike is.

Try 4th on these hills of yours and let the motor scream a little bit. It is, after all, a Suzuki. ;)

[Maggie]

Hey y'all! Just want to let you know I got the 16T sprocket and I am really liking it. Thanks for all the discussion here. What I really like is the nice long pull out of a stop. Don't have to shift as quickly to take her up to 2nd.

[jbaird]

I just got everything buttoned up after my test ride. The new sprocket seems to be a winner. The bike is very usable in 1st gear now and it still gets to 60 quickly. Cruising at 65 is no comfortable. I am sure this mod will add to the life of my bike. Thank you so much Jonathon

[bwader]

Like the sound of a big bore kit. Bumping up the displacement another 100 cc's or so would be a huge difference. The added displacement even in mild tune for reliability would likely allow for another tooth on the front sprocket and a couple less on the rear. Without going overboard this combo could be very nice for cruising the highways and give a longer, more powerful pull in every gear. But here is a less than great thought. Would the 250+ develope a vibration typical of larger thumpers ??

It would be nice to have a slightly bigger engine on the gz. Funny thing that is common with Itistheride forum and other scooter forums. People get a 50cc scooter and then get a BBK to make it 80cc's or 100cc's or even put a 150cc engine on a 50cc scooter body. They start going around 30-35mph maybe 40mph max then able to hit 40-45mph+ with big bore kits and taller gearing.

Then next 125cc upgrade to 150cc engine, then 150's scooters upgrade to 170-180cc's and go from 50-60+mph to 60-65mph+. Along with taller final gears as scooter are belt driven automatic CVT.

Then it comes to the 250cc class. About all these can do 60-70mph+ and then there are still people who are always wanting a little more power. Same thing, put in a bigger engine and taller gearing. There is always someone who gets something and wants to make it faster or better. I just like to do small things that make it better. I ordered the 16t sprocket myself and its a simple upgrade. I liked having a windshield on the scooter I had, I'd like to get one for my GZ for a better ride and less bugs hitting me.

I understand if you like what you ride and all you want is a little more power and top speed then you want to save money on a big bore kit and sprockets are inexpensive on bikes.

On Chinese scooters cheap as they are, you can buy a big bore kit for a $100-200 or so and put in taller final drive gears for 60-80 bucks if you press them yourself. So in that way it makes sense to spend a little more money on an upgrade like that.

Point is sometimes its just easier to trade up to the next engine size up, get a bigger bike that's ready to go stock for more power and speed. Which is why I got the GZ, its a good small bike and a big upgrade to any Chinese scooter. I don't mind tinkering a little but the Chinese scooter route is waaaay too much.Why buy something cheap just to have to upgrade better parts? Because its a lot of times cheaper to do that than buy a better name brand. Plus some people just like to upgrade

I just had to say all this, getting back on topic. A simple sprocket change to stress the engine less is a great idea. Can't wait to do mine.

[bwader]

Found this video on how to do it on the TU250X but its all pretty much the same.

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

[bwader]

I got to say, the 16t is smoother, tamer sounding. Got my digital tach. and the rpms are definitely lower in every gear. 1st gear at about 20mph indicated is 6,000rpms I didn't want to push it further.
I left for home after 11pm so it was too dark to tell exactly what rpms where unless under a street light at the right time.

I concur with everyone else it broadens out the range of the gears, I felt before even letting the engine rev for a few seconds before shifting it still seemed short time in between gear shifts. And I am gentle on the throttle.

When I adjusted the chain after putting the 16T on, for those who asked earlier I didn't have to tighten to much, maybe a full turn or so. I had to loosen up the chain and kick it in forward to get enough slack for the bigger gear.
I went from 57mpg to 64.8mpg going the same exact routes and riding the same. I ride at 40-45mph when I can or lowest rpms and now in 5th I can go as far as 3,400 to 4,000 rpms or around 35mph more or less. Mainly flat roads except for some inclines and declines I don't call "hills".
I can still hit 70mph gps as before just got to be in 4th and rev it there then go to 5th.

[Water Warrior 2]

Isn't it fun to actually kick your bike for a good reason?

[bwader]

Isn't it fun to actually kick your bike for a good reason?

It actually was nice! LOL

[steelpix]

Good write-up! I just ordered the new 16 tooth sprocket. I'll try it out and report back. I can always go back to the old sprocket if I'm not happy.

[golem]

Ok, so I installed a new front sprocket on my geezee and I simply don't recognize it anymore ! I was supposed to lose some speed ? Well , not in my case. It use to plateau at 60 mph and now I can easily reach 70mph !! I don't know why but I sure am happy about it. I also like the way the gears goes waaay better !
All in all, I recommend this mod to any owner of a gz even though YMMV. Thanks jonathan !

On a side note, would the bike benefit from a smaller back sprocket?

[beefjerky]

This looks great and I want to do this mod to my 2000 GZ

Which sprocket should I pick from these (http://www.amazon.co.uk/s/ref=sr_nr_i_0?rh=k%3AJT+16+tooth+sprocket+suzuki%2 Ci%3Aautomotive&keywords=JT+16+tooth+sprocket+suzuki&ie=UTF8&qid=1411035665&ajr=0)?

Apologies if this is covered in the thread already.

[golem]

I don't know if this is going to help you but this is the one I got :
http://www.amazon.com/gp/product/B001AVS6H2/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1

[Water Warrior 2]

You will know soon enough. Install the sprocket.

[Suzuki-san]

I bought the 16T JT Sprocket a while back, but finally got the nerve to do the swap. I'm glad I did, because the 30mm nut holding the 15T on was LOOSE! Thank goodness the bent washer was in place to keep it from unraveling! :eww:

Anyhoo, after studying the videos and reading this thread, and going over in my mind what I had to do, it was actually a pretty simple mod to do! :)

My experiences after the sprocket change to 16T is similar to other posters in this thread. I like that 1st gear is usable. The gears are spread out more, and it seems to run smoother. To me, the acceleration is as good if not better than before from start to 50+mph. I saw little or no loss in torque, esp. considering I am overweight by 100lbs or so. (curse you Krispy Kreme bacon donut dog... CURSE YOU!)

And as some of you have mentioned, and I am experiencing it as well, 5th gear is almost useless. At best it can hold a speed like 60mph. Try to accelerate, and it bogs down and goes slower. I guess it is too much for that engine to take the bike, my heavy self, a headwind plus doing 60mph, to do much more. The rest of the bike is stock. May consider rejetting the carb at a later date to compensate.

OVERALL I still like the mod. It is cheap to do and easily reversed if not satisfied. :cheers:

[raul10141964]

I recommend to mode the carburetor and air cleaner.
I wait 230 lb and hold 70 mi or more with no problems
I running a 140 main jet and mod factory air cleaner see the pic
The mode filter do not work with factory main jet

[PG tips]

I bought the 16T JT Sprocket a while back, but finally got the nerve to do the swap. I'm glad I did, because the 30mm nut holding the 15T on was LOOSE! Thank goodness the bent washer was in place to keep it from unraveling! :eww:

Anyhoo, after studying the videos and reading this thread, and going over in my mind what I had to do, it was actually a pretty simple mod to do! :)

My experiences after the sprocket change to 16T is similar to other posters in this thread. I like that 1st gear is usable. The gears are spread out more, and it seems to run smoother. To me, the acceleration is as good if not better than before from start to 50+mph. I saw little or no loss in torque, esp. considering I am overweight by 100lbs or so. (curse you Krispy Kreme bacon donut dog... CURSE YOU!)

And as some of you have mentioned, and I am experiencing it as well, 5th gear is almost useless. At best it can hold a speed like 60mph. Try to accelerate, and it bogs down and goes slower. I guess it is too much for that engine to take the bike, my heavy self, a headwind plus doing 60mph, to do much more. The rest of the bike is stock. May consider rejetting the carb at a later date to compensate.

OVERALL I still like the mod. It is cheap to do and easily reversed if not satisfied. :cheers:

I went looking for a JT 16T replacement sprocket online, I found different thickness 16T sprockets available, what thickness suits the GZ with stock chain? or does anyone have a part number?

Id toyed with the idea of getting a larger engined replacement bike, but for a few reasons that idea has fizzled out. Really the most cost effective thing for me to is just to try some of the simple mods on the GZ to try improve its characteristics which suit me well enough for what and how I use it already.
It'd be a shame not to try it really, and the idea of not having to change up a gear almost immediately sounds good. Dont know if a carb mod is needed or is better to do if changing the sprocket, which Ive read is recommended on another older thread

[raul10141964]

mod the carb and filter gibe you 1 to 2 HP more and make the engine rune colder

[PG tips]

I might try that too, but its not extra HP Im after in particular (is it a noticeable difference though?)
Making first useful and the prospect of the engine not reving as high as it seems to, is more what Im after, this seems to be described as the effect of changing the sprocket from a 15t to a 16t.

[raul10141964]

The extra hp Wil be noticeable on fifth giar

[jonathan180iq]

I might try that too, but its not extra HP Im after in particular (is it a noticeable difference though?)
Making first useful and the prospect of the engine not reving as high as it seems to, is more what Im after, this seems to be described as the effect of changing the sprocket from a 15t to a 16t.

Definitely. Lowering engine cruising speeds was my original intent and for that there is not an easier mod.

Also, as Raul said, up-jetting to a richer fuel mixture will help keep exhaust gasses a bit cooler and possibly help in engine longevity.

[PG tips]

Do either of these mods affect fuel economy? for good or bad

[raul10141964]

60 mph

[Water Warrior 2]

Do either of these mods affect fuel economy? for good or bad
Shouldn't be enough difference to sweat over at the pumps. A rider's right hand has a lot to do with economy.

[jonathan180iq]

Shouldn't be enough difference to sweat over at the pumps. A rider's right hand has a lot to do with economy.

+1

My fuel economy was very consistent throughout my ownership.

The sprocket didn't change anything for me, essentially. On long flat stretches, it increased my mileage. On very hilly terrain, my fuel economy decreased. the same would have happened with any sized sprocket.

[spldart]

I only just installed my 16t sprocket.
....
....
....
First impression is....
I absolutely love it!

I'll get some mileage numbers and impression of a long commute over the next few days.

Oh. And my primary goal is to reduce engine speed on freeway thus adding longevity.
We shall see how that plays out.

[spldart]

Mixed mileage on my commute is unchanged.
And since more rpm equal higher stresses on the engine, and this sprocket lowers engine
rpm in top gear on freeway about 7 percent, I'm thinking this mod is a great one to consider.
I love this mod.

[Vegas Street Rider]

After reading the various posts regarding the installation of a 16 t sprocket, I decided to try it for myself. Yesterday, I ordered the sprocket and am looking forward to installing it on my 2009 GZ. I will let you know how I like it. I always felt like I needed to grab another gear after 5th. This should satisfy that feeling.

Thanks for the detailed How To video. It's pretty simple, but following someone else's experience always instills confidence into a project.

[raul10141964]

I recommend to mod the carburetor to recover the lost of power with the 16t sprocket

Sent from my Z813 using Tapatalk

[spldart]

Link to carb mod of which you speak?
I wanna try.
Oh. And btw. Changing final drive ratio just moves the power. It doesn't lose it.
I did notice peak power rolls on around 65 mph or more whereas it used to come on sooner final gear.

[Vegas Street Rider]

How much torque do you need to tighten the nut for the front sprocket?

[Vegas Street Rider]

Put on the 16t sprocket on my 2009 gz. Haven't been able to take it on the beltway at higher speeds but definitely notice the difference in 1st gear and 4th since most of my riding is done at about 45mph on surface streets. I will update you all once I have had a chance to get her out on the highway. I have not noticed a need for the carb jet kit yet but I will consider it after I have ridden for a while.

[itsagz250butitsmine]

Thanks for the write up! The verdict is in, I just tried it out and the changes that I've experienced are that each gear adds about 5mph, which made 4th gear reach 70 now with the throttle pinned, but 5th gear had become even weaker:cry: now 5th gear maintains the speed and ever so slowly decelerates to 60. Still, better in every way except 5th, but I was expecting as much. :cheers:

[Vegas Street Rider]

Good news. You should eventually address the power issue though. 5th gear will add life to your engine by keeping the revs down at the higher speeds. Good luck.

[Razorburns]

One of the 1st things I did was put on a 16 toother (so easy to do, how could I not). I didn't get out much before the switch so I can't really comment on speeds before hand, but with the 16, I get around 65-70 mpg and comfortably hit 60. Over that it starts to get really buzzy and high revved.

Wondering about getting a 1 tooth smaller rear sprocket to take down the revs a bit more at the top end. From what I can tell, there still seems to be enough of power left, I'm just starting to run out of revs. over 65ish.

Insights?

[initialtvb]

So I've changed out the OEM 15T to the 16T, the problem is that I don't feel the difference.

I still have to change it at the same speed, if I wait for it to reach around 15, then the engine is revving way too high.

can anyone help me with this problem?

Please and Thank You.

[Vegas Street Rider]

Where you really gain with the 16t sprocket is on the higher end. There is a barely noticable advantage in 1st and 2nd but at higher cruising speeds, you can comfortably travel at 60 to 65 without the engine screaming for mercy. The big advantage to the 16t is that it will help prolong the life of the engine if you are constantly travelling at the higher speeds by reducing the rpms.

[kilo0195]

I also wouldn't drop the rear sprocket any with the 16t front. It may seem like it could handle it but these bikes make very little torque stick. Losing a tooth on the rear is just going to further reduce torque and the rpm difference will be negligible imo.

[wacio]

I left original 15 tooth sprocket in place. These engines are not pressure lubricated (10 psi oil pump just squirts oil on the moving parts). All crank shaft bearings are roller bearings. This type engines are designed more to run at higher rpm rather than higher loads. As proven by many there is no top speed gain to be had, just weaker acceleration netting performance loss. The only reason to to the swap is to limit vibrations at cruising speed. But vibrations are minimal any way (thanks to balance shaft).