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

[Water Warrior 2]

Originally Posted by Jvacustoms

I refuse to think that any manufacturer has ever gotten maximum performance outta any product.

The GZ is what it is. Third world countries probably account for 90% of GZ sales. Triple the HP of a GZ and see where the sales figures go..............straight down into the crapper. We are talking about performance of a different kind. Reliability is a performance category that beats gitty up go every time in the real world. Feel free to tinker all you want but don't criticize the GZ.

[Jvacustoms]

Originally Posted by Water Warrior

We are talking about performance of a different kind. Reliability is a performance category that beats gitty up go every time in the real world. Feel free to tinker all you want but don't criticize the GZ.

I agree that we are talking about two completely different aspects. However, i didn't come to this forum to ask for reliability answers i came here for horsepower gains and speed gains to make it faster. I know that the gz might not be the fastest bike around but the fact of the matter is, I don't care if it isn't i wanna see what i can get out of it without asking questions and finding out things that other people have tried and failed at, i would have to be really dumb. I want to see what it has not for reliability sake and really not for speed sake but for the sake of inventive engineering. Tinkering, as most call it. It gives me something to do that keep my creative juices going. I aspire that one day i will complete my own car fabrication from the ground up but until then i am starting with a great base and customizing it and changing it to learn more about it, and if i screw it up then I am out nothing because i learned from the experience and i get to take that with me even if the low budget bike that i got for free, gets parted out to other people on this forum or eBay or other places. (pieces and parts that haven't been modified or changed in a unwanted manner)

And furthermore I wasn't criticizing the GZ merely my opinion on whether the manufacturer has taken the time to make things perfect, but perfection is only perfect in the eyes of the original designer. The concept of a GZ being based on a Low budget market for people in third world countries make it that much easier for a non third world country to customize and just possibly improve on.

[Water Warrior 2]

Big A+ for attitude. Keep tinkering, I want to see what you come up with in the future.

[Road_Clam]

Gearing is all about "compramise" it doesn't matter weather you have an 1100 cc bike with 120 hp, or a 250cc with 18 hp. Here's a few basic points for those who are curious. As you gear "lower" ie swapping from a 16T countershaft sprocket to a 15T you will gain acceleration as the engine is now allowed to rev quicker, and less engine torque is required to get the bike moving. Your peak rpm's are also matched to a LESSER top speed vs stock. When you gear higher (swapping from a 16T to a 17T ) you "in theory" should gain top speed.
The issue is with "theoretical" is that the gearing caculators that are available on the internet do not factor "real world" variables such as "rolling resistance" and "added mass". These two major factors play a large role in negating the presumed effects of gearing higher for increased top speeds. Basically if your engine doesnt have adequate hp that's required to pull higher than stock gearing, you most likely LOOSE top speed, as now the engine cant reach peak rpm's. Now if you take everything iv'e said and reverse the facts this is how gear changes effect REAR sprocket changes, so swapping a 38T to a 37T rear sprocket is actually reversed, and you are now gearing higher. I'm sure that The GZ is geared for a "compromise" of both power and top speed from the factory, you can always gear lower as you are now freeing up required hp, but i doubt if there is much extra hp available for gained top speeds given the purpose and cc limitations of the GZ. I just picked up a sweet '01 GZ250 for my wife, and I spent the whole weekend going through the bike, and I am impressed, what a fantastic 1st bike for a person ! I obviously have not spent enough time with our new to us GZ to make a call on a gearing change, i just wanted to share some good gearing knowledge..

Rich

[JWR]

The GZ is a good bike. It will take a lot of abuse and keep on ticking.
I put over 15,000 mile on mine and the only problem I had was the fuel screen came off in the tank.
this let a piece of trash get in the carb. I took the carb off cleaned it and keep on truckin!!

:2tup:

[Water Warrior 2]

Road clam, just looked at your list of 2 wheelers. I would guess you have had fun with different gear ratios on various bikes and your real world experience will be an asset for all members here. Welcome to the forum.

[Road_Clam]

Originally Posted by Water Warrior

Road clam, just looked at your list of 2 wheelers. I would guess you have had fun with different gear ratios on various bikes and your real world experience will be an asset for all members here. Welcome to the forum.

I actually did a lot of gearing experimentation with my '82 GS1100E . The issue I had was too high rpm's for cruising at 80 mph on the highway caused a bad "bar buzz" at around 5100 rpm's . So I changed the gearing from 17/42 to 17/40 and it was just enough to bring down the highway cruising rpm's about 300 rpm's minimise the bar buzz. I also have done a ton of gearing swaps on my motocross bikes depending on the reqiured terrain. Thanks for the warm welcome !

[riningr]

I just bought a 2000 GZ250 and have only put about 50 miles on it, so far I like it for a good economical bike to save on gas, the only complaint I have is trying to maintain speed going up hill / against wind on the highway... I've read through quite a few posts on here and been playing around with gearingcommander.com but curious if I am interpreting the information I'm reading correctly...

From what I've read the GZ250 is redline at 8000 rpm, peak torque is (14.0 lbs ft) at 7000 rpm, so I'm assuming the reason I'm losing speed while climbing hills or against wind on the highway is because I'm riding wide open throttle to hit 75 on the highway which would put me close to redline (gearingcommander says 75 with stock sprockets would be 7539rpm, but I'm assuming I'm actually closer to redline because of my weight its taking more to get me to 75, assuming of course since it has no tach). I haven't tried downshifting on the highway, but I did on a backroad doing about 60 and it seemed to help hold my speed a little better... so I've been reading about sprocket changes and I'm wondering if I change from 15/41 to 16/41 it says that it would drop the RPM's at 75 down to 7068 which would put me pretty close to peak torque which should help me maintain 75 better against wind / going up hill wouldn't it?

But from what I've been reading it seems like everyone is going after higher top speed, I'm more than happy with 75 on the highway and 60 on main roads as long as I can hold the speed against the wind / going up hill... it seems like I need to go to 16/41 and then being closer to peak torque should help me maintain the speed?

[blaine]

Welcome to the forum.The 16t front sprocket is good for lowering the R.P.M's that make the lower gears more useable around town & flat roads.The bike does not have enough power (torque) to keep the revs up on hills unless you want to stay in 4th gear longer.
:cool:

[JWR]

Originally Posted by riningr

if I change from 15/41 to 16/41 it says that it would drop the RPM's at 75 down to 7068 which would put me pretty close to peak torque which should help me maintain 75 better against wind / going up hill wouldn't it?

But from what I've been reading it seems like everyone is going after higher top speed, I'm more than happy with 75 on the highway and 60 on main roads as long as I can hold the speed against the wind / going up hill... it seems like I need to go to 16/41 and then being closer to peak torque should help me maintain the speed?

The 16 tooth sprocket is very limited in where it will run.

Flat ground and no wind. If you vary out of this zone you will be in 4th, but 4th will be almost as fast as the 15 in 5th.

There is no real torque in top gear.