Modifying the GZ250 - What's Available

[jonathan180iq]

After learning to ride somewhat proficiently, most new bike owners soon get a desire to change certain parts of their bike to either make it more their own, add useful/comfortable accessories, or would like a little more performance.

I plan on using this thread to outline what works and what is available, based on a general forum consensus, and not my own personal opinion.

Each modification will have it's own post and will be updated as new information is acquired.

Let's begin...

[jonathan180iq]

Possibly the easiest mod that you can do which will have a pretty drastic change to the way your bike performs is to change the final drive gearing.

The final drive of the GZ250 is a simple chain/sprocket combo. The final drive ratio is 2.73. This number is easily calculated by dividing the number teeth on the rear sprocket by the number of teeth on the front sprocket. In our case, since we have a factory sprocket combination of 15 and 41 (15 teeth in the front and 41 in the rear) the calculation would look like this.

41 / 15 = 2.73333333 (or 2.73)
The lower the gearing, the lower the revs. The higher the gearing, the higher the revs.
You'll almost never want to change any sprocket more than one or two teeth sizes in any direction over the factory number.

By comparison, switching over to a 16T front sprocket lowers the final drive ratio to 2.56 (41/16)

What does this mean in practical application?
The 16T front sprocket lowers cruising revs in all gears and allows the lower gears to be used for a longer period of time. However, you will probably notice a drop off in your top speed. While the factory gearing allows the GZ to reach somewhere around 80mph, the 16T front sprocket will lower that to around 70mph. The reason being that the internal gearing of 5th gear has a ratio of .818, which is basically an internal overdrive and seems to make the gear too "tall" for the mighty GZ to handle.


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)

http://www.postimage.org/PqHgVm0.jpg (http://www.postimage.org/image.php?v=PqHgVm0)

How do I change my front sprocket?

http://www.gz250bike.com/viewtopic.php?t=317

[Easy Rider]

I plan on using this thread to outline what works and what is available, based on a general forum consensus, and not my own personal opinion.

Each modification will have it's own post and will be updated as new information is acquired.


How about we give this a little more thought before we get carried away ?? ;)

We already have a FORUM titled "GZ Bike Mods".

Within that forum, we already have individual topics covering a LOT of the mods......each with an apporpriate title describing briefly what the mod is....(some may need to be changed).

I think trying to establish one single thread with all the mods covered is NOT the best way to go.

Maybe some of the existing threads need to be cleaned up, organized, things added (and some bad info. deleted......like references to a non-existent big bore kit) but I just can't see the logic behind creating a thread like this IN ADDITION to what is already here.

You get a hearty ATTA BOY for your idea and efforts. I just think there is a better way......that might work out to be easier in the long run.

[jonathan180iq]

I'm just trying to streamline to process.

It would certainly be less work but I've read several requests for an organized one-stop-shop for aftermarket parts and I have most of the information saved in my GZ file. So, I figured why not go ahead and get it started.

If no one feels that it would be useful, it can always be removed. I'll save it of course, 'cause I've put a lot of time into it.

I'm by no means the GZ250 guru (just overly active because I thoroughly enjoy two wheeled transportation) but, personally, before I came across this forum there was pretty much no easily accessible information on what has or could be done to GZ. Since this site has started growing, and more contributors have added their piece, I just thought it was high time for an easily researchable file showing what others have done, what is available, where to get it, and what might happen if it's bought.

It's about as close to it comes as having an FAQ without actually having an FAQ, and while still being open to discussion. The ability to read the other posts and get differing opinioins is still there, as this is still an open forum.

For example, instead of having to read through 20 posts about oil or sprockets (or BIG BORE KITS! AWESOME!!!!) anyone on the foum can swing in here and get ideas of what is out there. Hopefully it will kick-start the knowledge of the first time rider as to what it available.

As I said, everything that I post is up for discussion and I have no problem changing what I say to be more inline with the general consensus, if that needs to be done. I'm trying to leave opinion out of it and just state facts on each individual item.

[Moedad]

I really like the idea of a streamlined thread of mods. I've spent a lot of time wading through the Mods forum and, yes, there is a ton of fantastic info there, but much of it has to be sifted out of the "I agree" or "What worked for me" and general mod chatter. That takes time. Whether it's easier to clean up the existing mods threads or to do what Jonathan has begun here, I don't know, but streamlined is good! :2tup:

[jonathan180iq]

If there is one draw back to commuting by motorcycle, it's that there is no where to store your junk while riding.
That's why a whole slew of companies make motorcycle specific luggage.

If you decide that simply wearing a backpack isn't enough for you, then you might be interested in some of these options.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Since there is such a wide variety of products available, we won't go into specific detial but rather outline what it most commonly used. For other opinions on exactly what others are using and what is preferred, you'll have to check the forum and search a little bit. Sorry Charlie.
Saddlebags

http://www.postimage.org/gx2mkByA.jpg (http://www.postimage.org/image.php?v=gx2mkByA)
Photo property of JNorton

There are a million different places to purchase saddlebags. The company that you purchase from is your choice. It's important to remember, however, that the GZ250 is a rather small bike and some of the larger saddlebags seem out of proportion. So make sure that you get some rough measurements so you know what size bags to shop for.

Also, you'll need to purchase (or make) saddle bag support brackets so the saddlebags don't rub against your wheel, or get caught in the spokes or some other crazy scenario.

Where can I get saddlebag supports?

http://www.postimage.org/gx1POxsS.jpg (http://www.postimage.org/image.php?v=gx1POxsS)

You have three options. You can purchase the factory supports, which cost a good chunk of change, you can buy aftermarket supports which cost a little bit less, or you can fabricate your own using some parts from your local hardware store. This last option will cost around $15, depending on inflation. :)

Any idea where to purchase support brackets?
Go to you local Suzuki dealership and ask...
Or
Type in a search on Google...?
Or
Go to this website:
http://www.mcenterprisesusa.com/product ... chForm.cfm (http://www.mcenterprisesusa.com/products/search/dsp_searchForm.cfm)

What about making my own?
Props to Tonckawa for doing this write-up.
http://www.gz250bike.com/viewtopic.php?t=961

or here:
http://www.motorcycle-journal.com/forum ... -made.html (http://www.motorcycle-journal.com/forum/cruisers/14946-12-gz250-saddlebag-supports-home-made.html)

What about hard saddlebags?

These generally cost more than soft saddlebags and, like with soft bags, you'll need to measure and remeasure to make sure that they fit properly. Also, as with soft bags, the options are just about limitless and you'll have to make your own decision on who to buy from.

Ammo Can Saddlebags
A rather sturdy and lockable option which only costs a fraction of "real" hard cases is to fit surplus military ammo cans in place of the saddlebags.

Mad props to Badbob, and others, for their write-up on how to install ammo cans on the GZ.
Follow this link for a How-to and discussion on the install:

viewtopic.php?f=3&t=87&hilit=ammo+cans (http://www.gz250bike.com/forum/viewtopic.php?f=3&t=87&hilit=ammo+cans)

http://www.postimage.org/PqHLhvA.jpg (http://www.postimage.org/image.php?v=PqHLhvA)

[jonathan180iq]

Rear Mounted Trunks (Luggage Racks)

Another lockable option is the top case. These are basically trunks which can mount to your rear rack, if you have one, or can be mounted directly to the rear fender, if you feel like modifying it.

As noted, you'll need a rear rack, which, like most things, can be purchased from many different places. The factory sissy bar/rear rack combo can cost as much as $300. A simple model, pictured below, will cost around $100. Just do a Goggle search and you'll find them. You need to make sure that you are buying a rack that is designed for the GZ.

For a little help finding one, try this link: http://www.mcenterprisesusa.com/garage/blowouts.html
Use this part number : 121-25 Dlx Rear Mini Rack Suzuki GZ250 '99-'04 $95.00

http://www.postimage.org/gx1PUh8A.jpg (http://www.postimage.org/image.php?v=gx1PUh8A)

Like saddlebags and the like, there are many different designs and styles of top cases. Most of them come with universal mounting hardware, so the way that you mount these things is really up to you.

There are high-end companies, like Givi, which price their top cases around $200. Generic models seem to work just as well and range in price from $50-$150. An Ebay search or a visit to www.jcwhitney.com (http://www.jcwhitney.com) will turn up loads of the generic models.

http://www.postimage.org/PqHN6f9.jpg (http://www.postimage.org/image.php?v=PqHN6f9)

Can I mount a top case without buying a rear rack?

You sure can.
See Happyhobo's Write-up on how to install a trunk to your rear fender:
http://www.gz250bike.com/viewtopic.php? ... k+mounting (http://www.gz250bike.com/viewtopic.php?t=286&highlight=trunk+mounting)

http://www.postimage.org/gx1PYXtr.jpg (http://www.postimage.org/image.php?v=gx1PYXtr)

[jonathan180iq]

Many Gz riders complain about the factory seat compressing after a short period of time and not providing enough cushion.

There seem to be only a few DIY options available, as no company makes an aftermarket seat for the little thumper and there are no seats from other bikes which will fit.

Badbob has done the most work in the seating department. He had Sargent Cycles custom design a seat to fit the GZ. I believe that this is still something that is only produced when requested.

See his post:
http://www.gz250bike.com/viewtopic.php? ... ht=sargent (http://www.gz250bike.com/viewtopic.php?t=111&highlight=sargent)

http://www.postimage.org/aV1UiehJ.jpg (http://www.postimage.org/image.php?v=aV1UiehJ)

Can I do anything to improve the seat?

Luckily there are a few ways to improve the cushioning of the seat without having to spend big bucks on a custom design.

Several members have simply added motorcycle specific gel pags to their seats and were satisfied with the improvements.

Another option, which might be aesthetically appealing, would be to remove the factory seat cover and install some type of padding. Then, you could recover the seat with the material of your choice and you would, effectively, have a custom desinged and more comfortable seat.

-For a quick how-to on shaving the foam from your seat or for how to recover it, see this link:
http://www.gz250bike.com/viewtopic.php?t=628

-Mr. Softie has completely replaced the foam in his seat. See his thread here:
viewtopic.php?f=9&t=1599 (http://www.gz250bike.com/forum/viewtopic.php?f=9&t=1599)


Lastly, you can simply cover your seat with a sheep skin cover or anything in between. It's ultimately up to you.
http://www.postimage.org/aV1UiSc0.jpg (http://www.postimage.org/image.php?v=aV1UiSc0)
http://www.postimage.org/aV1Uk0x9.jpg (http://www.postimage.org/image.php?v=aV1Uk0x9)
http://www.postimage.org/PqUS6gi.jpg (http://www.postimage.org/image.php?v=PqUS6gi)
http://www.postimage.org/gx21sA3S.jpg (http://www.postimage.org/image.php?v=gx21sA3S)

[jonathan180iq]

There aren't many tire options for our bike that come in a matching set. There are, however, many options if you don't mind mixing up tire brands and/or going to a slightly smaller tire up front.

The factory tires sizes are: 110/90-16 (F) & 130/90-15 (R)

The rim width for the front wheel is 2.5" and the rear wheel width is 3.0"
That being the case, a size 100/90-16 front tire will work on this bike. It does have an overall diameter decrease of 9mm over the 110/90-16 but that isn't really very drastic.

Samato has verified that alternate tire size 100/90-16 will mount up with no problem.

As well, the 120/80-16 alternate tire size is another choice for the front tire and has been successfully mounted by MRLMD1.

Factory replacement tires: 110/90-16 & 130/90-15
Dunlop D404 (only available through a Suzuki dealer)
Metzeler ME77 (only available through a Suzuki dealer)
Cheng Shin C906 & C907 (possibly no longer available)

Rear Factory Replacements: Kenda Challenger
Pirelli MT66 (Route 66)
Maxxis M6103
Cheng Shin Marquis
Metzeler Me 77

Factory Replacement Front:
GBC Green Shark
Metzler Lasertec
Pirelli Sport Demon
Avon Roadrider AM26
Conti Ultra TKV11
Kenda K671 & K673

100/90-16 Front: Bridgestone BT45
Maxxis M6002
Cheng Shin C6000
Kenda Cruiser
IRC Durotour

Matching tires with low profile front: 100/91-16 & 130/90-15
Kenda Cruiser
http://www.postimage.org/gxMKLT0.jpg (http://www.postimage.org/image.php?v=gxMKLT0)


For more discussion and lots of info, see these posts:

viewtopic.php?f=10&t=722 (http://www.gz250bike.com/forum/viewtopic.php?f=10&t=722)

&

viewtopic.php?f=10&t=1818 (http://www.gz250bike.com/forum/viewtopic.php?f=10&t=1818)






This list is not complete but will be updated as more options are discovered.

[jonathan180iq]

If you decide that you want to "enhance" the appearance of your tail lights or turn signals, you have a couple of options.

You can change out the tail light housing for a clear housing with and LED board. You can alter the color of the turn signal lenses. Or, for a little more contrast in lighting and a little less money spent, you can alter the power of the bulb in the tail light and replace the turn signals with LEDs. As of today, no one has experiemented with LED turnsignals. On some bikes, the replacement of the standard filament bulb with an LED buld reuslts in fast flashing and low light output.

You can get the lenses for the brake light in CLEAR. Turn signal lesnes are available in either CLEAR or SMOKE variations. Please consider the visibility of the turn signal or brake light, if you choose to alter the lense color.

Clear Tail Light Lense

http://www.postimage.org/gxSfwe9.jpg (http://www.postimage.org/image.php?v=gxSfwe9)

http://www.denniskirk.com/jsp/product_c ... Id=&mmyId= (http://www.denniskirk.com/jsp/product_catalog/Product.jsp?skuId=211181&store=Main&catId=&productId=p210670&leafCatId=&mmyId=)


These are clear tail lenses and LED tail light options that are a direct replacement for the factory housing.

These can also be purchased from a company called ClearAlternatives.
http://clearalternatives.com/Merchant2/ ... e=Marauder (http://clearalternatives.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=CA&Category_Code=Marauder)

Turn Signal Lense

http://www.postimage.org/Pq1nhAT0.jpg (http://www.postimage.org/image.php?v=Pq1nhAT0)

Again, these can be purchased from either DennisKirk or ClearAlternatives.

http://clearalternatives.com/Merchant2/ ... =CRUISERSS (http://clearalternatives.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=CA&Category_Code=CRUISERSS)

It may be possible to find replacement lenses from more distributors. Most of the Suzuki cruisers share the same turn signal lenses. So, if you can find them under a different model, they should fit. Just make sure you get the standard ciriclualr lense.

For a chart showing alternate bulbs which will fit the GZ and their power and light output ratings, see this link:
http://faq.ninja250.org/wiki/I_want_tai ... 6_contrast (http://faq.ninja250.org/wiki/I_want_tail_lights_with_more_brightness_%26_contra st)

[jonathan180iq]

If you're looking for 100mph and a big increase in horsepower, you've come to the wrong place and you're probably riding the wrong bike. The Gz250 will never be a "pull-your-arms-out-of-the-socket" kind of bike. You can however, tweak the exhaust and/or air filter and carb jetting to achieve a slightly better than stock power delivery.

How do I do it?
There is really only one way to increase the power output of any motor vehicle and that is to correctly & proportionately increase the amount of air and fuel that goes into each cylinder. On a carburated machine this is particularly important because increasing the amount of either of these two factors will have adverse effect on the other, if their proportions are not balanced.

For example, as simple a change as having a disconnected crankcase hose will make the bike ping and pop and will leave it basically unrideable over 30 mph. There is a proper balance of the air to fuel ratio and that is 14.7:1
http://en.wikipedia.org/wiki/Air-fuel_ratio

Jaime has an excellent write-up on how to rejet your carburetor when working with a high flow air filter or an exhaust change. Read it thoroughly. Jetting will be different on almost every bike and you need to know what you are doing before you start just taking things apart. That being said, it's not all that difficult, once you know your way around.

See Jaime's write-up here:
viewtopic.php?f=8&t=617 (http://www.gz250bike.com/forum/viewtopic.php?f=8&t=617)

Disclaimer:
Some people consider this mod to be not worth the hassel, as it doesn't provide a mind-blowing difference and takes quite a bit of work. Be sure you know what you are doing before you go in there and screw something up. An imporperly jetted bike is about as much fun to ride as a epilectic cow.