Gears... 15/41 Stock v.s. 18/38 mod

[Water Warrior 2]

Originally Posted by 5th_bike

Well you could switch down to 4th gear. At 65 mph in 4th gear the engine runs at 8,000 rpm which is not redline but the bike does not like to do such high rpms for a long time. At least in 4th gear you could easily go 50-55 and not blow up the engine.

PS WW - sorry but your 27% is kind of, um, off - you add where you should multiply. Look at my earlier post how to calculate the percent change in gearing, just multiply the two increases: (18/15) x (41/38) = 1.29... which is 29..% more. Moot though.

Close is good for an old guy. :lol: :lol:

[Jvacustoms]

I know it is a gz I just want to get better performance for what I have while I am building my goldwing I also think that the gz has a lot of potential to be a really fun bike but I just wanna make it be comfortable to ride and be able to keep up with my buddies rebel

[jonathan180iq]

Taken from: viewtopic.php?f=9&t=1058&hilit=modifying+the+gz
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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.

EDIT FOR THIS CONVERSATION: Imagine what this would be like with a 18T front sprocket.... On top of that, I highly doubt that an 18T front sprocket will even fit on this bike. There is a sprocket combo that should allow for decreased highway revs while also extending reducing the drain on the final drive and it is 16/42 or 16/43. The gearing ration on both of those works out to be 2.62 & 2.68 respectively. That falls on a nice medium in between the factory gearing and the overgearing of the 16T in 5th.


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)



How do I change my front sprocket?

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

[Water Warrior 2]

Interesting info. I think the smallest gearing change might be the biggest overall advantage.

[jonathan180iq]

I completely agree. I wanted to try my suggested gearing combo but sold the bike long before the funds matched the desire.

I would think with this set up you could use the same chain. But rear sprockets cost somewhere around $45 so you really have to be in committed to getting perfect gearing. That being said, if you keep this bike for any significant amount of time, it makes sense to invest maybe $100 total and get a gearing that you are completely satisfied with.

I didn't post this in the previous little bit, but the gear ratio that the original poster suggested is 2.11 final drive.

2.11....

I don't know that you would even be able to get the bike to move forward in 1st gear. It would stall out.

[Water Warrior 2]

The cost commitment wouldn't be so heart stopping if you wait till you need to replace the chain and sprockets due to wear. I would be tempted to wait till the parts were due for a R+R. You know you will have to do it eventually.

[Jvacustoms]

well i am gonna be doing the rear tire and brakes this month some time so i figured that it would be a good time to do it for mine. Also I am just now really getting to parts that have either rotted due to sitting and such cause it sat so long. THe back tire was dry rotted on the surface but under that was still a good tire. The chain just needed to be cleaned and the brakes all together fell apart over the course of the last 2 months so I will have to replace them too. I am thinking about doing the drill on the exhaust and the 130 main jet. I cant afford all that other stuff and the k & n air filter so i don't know if i should do the rejetting until I get that air filter too. I like riding the bike and I like the fact that I have already found some other 250 riders to ride with but at the same time all the other 250's are faster than me and typically leave me and I have to catch up at the next stop. I like the looks ofmy bike and the cost to get started riding but I have never had a vehicle that had less power than those i was around and I just want to remedy it enough to keep up with the Jones' and enjoy the bike as I save money.

[JWR]

I was just up the road from you Sunday at Dahlonega, GA.

That is one of our breakfast rides, right at 300 miles.

The easiest and cheapest way to get the GZ to be a fast bike is to become a better rider.

[Water Warrior 2]

If the front tire is as old as the rear it will have to go too. After 5 years the rubber dries out and will not grip nearly as well. Good tires are an excelant health insurance plan.

[jonathan180iq]

Originally Posted by Jvacustoms

well i am gonna be doing the rear tire and brakes this month some time so i figured that it would be a good time to do it for mine. Also I am just now really getting to parts that have either rotted due to sitting and such cause it sat so long. THe back tire was dry rotted on the surface but under that was still a good tire. The chain just needed to be cleaned and the brakes all together fell apart over the course of the last 2 months so I will have to replace them too. I am thinking about doing the drill on the exhaust and the 130 main jet. I cant afford all that other stuff and the k & n air filter so i don't know if i should do the rejetting until I get that air filter too. I like riding the bike and I like the fact that I have already found some other 250 riders to ride with but at the same time all the other 250's are faster than me and typically leave me and I have to catch up at the next stop. I like the looks ofmy bike and the cost to get started riding but I have never had a vehicle that had less power than those i was around and I just want to remedy it enough to keep up with the Jones' and enjoy the bike as I save money.

I'll go ahead and warn you right now... drilling the exhaust is a waste of time. It doesn't flow better, it sounds like crap, and a 130 on top of that is going to leave you running rich.

For about $60 you can chop off the rear muffler section and install an EMGO universal muffler and get a much better sound and better flow. Then, you can add a 130 and it will be about right. For slightly more air flow through the intake, just pull the snorkle off of the airbox and leave it alone. The stock filter is better at trapping contaminants than anything aftermarket, although it is the most restrictive part of the whole thing.

If funds are limited, I think this is your best bet. You don't have to pay for an expensive exhaust set-up and you get better intake flow without having to replace the filter or hassle with removing and replacing the airbox and the corresponding air hoses.

I'll say it again: Punching holes in the exhaust, or puncturing the baffle will just leave you disappointed in the long run. Trust me. I have been there. I even posted a video of it on Youtube. (Marauder GZ250 Exhaust Comparison) I hated it so much I spent $600 buying the a brand new factory system.

After you do all that and get the bike running right and sounding how you want, then save up $100-$150 and do the gearing/chain upgrade that has been suggested.