Mileage and Speed [Archive]

Gadzooks Mike

09-02-2007, 10:39 PM

I used to think that folks who said they got 85mpg on a regular basis needed new calculators, and those who said they regularly travelled at 85mph we using metric miles or something. However, I'm thinking that there are two or three distinctly different GZ250 bikes and we haven't picked up on that yet. Here's a couple of examples:

I rode with a group not too long ago, and three of the group rode GZ's Two of them the same model year and color but one got 65mpg and the other got somewhere around 85mpg, both travelling together at the same speeds. Another person here owns two and the two get very different miles per gallon.

The next case is a person who has a GZ and put a 16 tooth front sprocket and can no longer get his bike moving faster than about 60 mph, while I can get mine up to 65-70mph on level ground with a 16 tooth sprocket. His friend can run 75 or so with a 15 tooth front sprocket.

I'm not sure if other mods have been made here with some of these, specifically the needle mod to rich up the mix a bit. However, it seems as if the differences are BIG and seem to just happen at random.

So, let's hear it. Anyone have any ideas or anything about this? Are these things being made at two different factories or something? Different parts? Different ???

Badbob

09-03-2007, 09:52 AM

Yep, there is definitely something different.

It doesn't need to be big. Parts made by different subcontractors with somewhat different tolerances and different combinations of these parts might do it. Tiny differences in carburetor could make large differences in gas mileage.

Jaime

09-03-2007, 01:53 PM

There's a similiar mistery here in Spain. Talking about stock bikes, they run from 50 mpg to 80 mpg. Sometimes it's caused for the riding style, but in other cases there's no explanation. They're mounted in Spain, but some pieces -like the engine- come from Japan.

Depending on which bike, they ride from 72 mph to 86 mph; for the top speed, and from 60-65 mph to 75-80 mph; for the cruising speed. Such big diferences for the same model. :??:

jonathan180iq

09-03-2007, 03:42 PM

I can't figure it out. I get the same mileage as always but, as you mentioned, can't break 60MPH at full throttle and I'm a lightweight. My buddy can shoot 80 with a 15T sprocket and he's a middle/heavy weight.

That being said, I get better mileage than he does.

I would guess that it has to do factory jetting and location. However, with the two bikes I am familiar with, they were purchased at the same store 2 months apart and we live in the same town. I don't know if they came from the same facotry.

jonathan180iq

09-03-2007, 03:44 PM

Badbob

09-03-2007, 08:28 PM

Went riding with my wife today. 148 miles her mileage 75mpg mine 58.

Gadzooks Mike

09-03-2007, 10:34 PM

Amazing. And since you were both travelling together, you must have done close to the same as far as stopping and starting goes. That's really quite a difference, too - about 25% or so.

You were wondering how long these chains last before they need to be replaced, and now I'm wondering where I'll get another 16T sprocket to put on with the new chain. Does anyone know if Suzuki makes them or has them or ???? I would sure hate to go back to 15T.

Easy Rider

09-04-2007, 09:59 AM

You were wondering how long these chains last before they need to be replaced, and now I'm wondering where I'll get another 16T sprocket to put on with the new chain. Does anyone know if Suzuki makes them or has them or ???? I would sure hate to go back to 15T.

Yikes. You HAD to bring that up didn't you!
Actually it is good that you did; I hadn't even thought about it.
I saved my original 15T just incase.

I'm a little reluctant to even say this 'cause somebody is bound to mis-interpret, twist, take out of context or otherwise mangle it but here goes anyway:

If you keep a close eye on chain wear and change it before it is really worn out, you might be able to keep the same sprockets through more than one chain. Depending upon conditions, the chain usually wears more and sooner than the sprockets. It is best to change them together as a set but if you watch things closely, it may not be totally necessary.

Gadzooks Mike

09-04-2007, 11:59 AM

I have no proof of this (as usual - I guess a lot), but I'll bet some of this is exactly the same as the JT sprocket:

http://www.harris-performance.com/websi ... atalogBody (http://www.harris-performance.com/website/acatalog/index.html?http%3A//www.harris-performance.com/website/acatalog/Suzuki.html&CatalogBody)

Seems to me that most 16T sprockets made for a 525 chain would work. Anyone have any thoughts?

Easy Rider

09-04-2007, 12:34 PM

Seems to me that most 16T sprockets made for a 525 chain would work. Anyone have any thoughts?

If the "hole" in the middle is the same.
That part is kinda important too! :tup:

Gadzooks Mike

09-04-2007, 02:47 PM

Well, yeah. What I'm saying though, is that I'll bet (a cold beverage of your choice) that they're all off the shelf parts and not specific to Suzuki, just to a 525 chain and assembly. I doubt Suzuki stamps out sprockets, but instead gets them from Spacely, and it's probably the same sprocket used on a bunch of stuff, not just Suzuki. JT isn't going to make them anymore, but somebody is. :tup:

jonathan180iq

09-04-2007, 04:47 PM

If you look on the JT website, they have a cross reference chart and you can match up dimensions from sprockets for other bikes. Then, even if Jt doesn't have it, you can search for that sprocket made by another manufacturer.

Jaime

09-04-2007, 05:42 PM

I've been searching for similar sprockets at the JT website for a while, and the only one a bit similar is the JTF 432, but there's no 16T version :mad:
http://www.jtsprockets.com/fileadmin/Code/images/small/jtf434.jpghttp://www.jtsprockets.com/fileadmin/Code/images/small/jtf432.jpg

I can't believe they're discontinuing this model, can't GZ250 owners even replace their 15T sprocket for the same one?

Anyway, if you really need a longer ratio, you can buy the JTR 819.39 rear sprocket and make the bolt holes bigger. You'll get slightly shorter gears; that means, at 6500 rpm in 5th now you do 69 mph with a 16T, you'll do 67 mph using a 15T front / 39T rear, while stock speed is 64.6 mph at same rpm.

http://www.jtsprockets.com/fileadmin/Code/images/small/jtr819.jpg

I've made an Excel table to calculate speed variations because of sprocket changes, but it's in km/h. :roll:

Jaime

09-04-2007, 06:03 PM

Well, I've converted the xls chart for you. Now it's in English and in mph. :tup:
It can be used for any bike, knowing the gear ratios and the tire that mounts. You can only modify yellow cells, so there's no way to ruin the file. :tongue:

http://rapidshare.com/files/53542278/RATIOS.xls.html

I hope it serves you!

Water Warrior 2

09-04-2007, 06:54 PM

To the best of my knowledge Sunstar used to make sprockets for Suzuki, probably still do if that helps.
Years ago( this was a fun exercise )a friend of mine wanted a one tooth smaller front sprocket for a 1988 DT 200 Yamahussy. Dealers would not even look beyond the factory parts book and said you are SOL. A kindly parts guy at a Honda dealer went through his entire stock comparing sprockets and Bingo, we had one. Was for a 125 CR motocrosser. After getting a couple longer bolts and extra washers for the install the bike was climbing hills far better and had some real get up an go.

Gadzooks Mike

09-04-2007, 10:28 PM

Thanks, Jaime!!

Water Warrior, that's my point exactly. I've got to have a talk with George Jetson. He works for Spacely Sprockets, and I'm pretty sure he can find one that fits. In the meantime, I'll see about Sunstar! :tup:

Regular Guy

11-26-2007, 01:12 AM

Hey fellas,

I bought my 16T sprocket from Rebel gears, they make a lot of their own gears but got this one for me from one of theri suppliers. I'm not sure who, but we discussed it a bit and Rebel guy told me it was the same except had a boss shoulder, to try it and see if it works. It did-perfect fit. can remember exactly, maybe about $20 + dollars.

Just thought you would like to know!

ps: can anyone tell me how to insert a link with this editor?

Is it like this [www.rebelgears.com][/url]

trykemike

11-26-2007, 01:38 PM

Glad to hear from you Mike.

Re: the different models SUZUKI installed the 250 engine in several different models from the early 80 until present

they are :

GN250 , TU250 , GZ250 , Marauder 250 .

I have read power ratings ranging from 15.2 lbs torque @5500 rpm and 22 hp @ 8500 rpm to
14.8 lbs torque @ 7000 rpm 20.6 hp @8000 rpm.

gear ratios are the same only wheel sizes vary but so also do the tire profiles.

dry weight ranges from 285 to 305 lbs

there are some jetting differences 115 main vs 120 main jet

I have a tach so I know my bike will rev to 8000 rpm in 4 th and 7750 in 5th because I have done this many times.

It may even hit 8000rpm in 5th but I never have enough space to try it ( usually 1/2 mile ) clear max.

I have checked the spark plug it was a light tan color .

Badbob

11-28-2007, 07:11 PM

http://www.suzukicycles.org/photos/TU/TU250-Bigboy/2002_TU250-Bigboy_top_450.jpg

I like this one. Note the kick starter.

Badbob

11-28-2007, 07:33 PM

http://www.robertkeeney.com/gallery/d/5855-3/Suzuki_GN250_New_Zeland.jpg

I like this one even better.

jonathan180iq

11-29-2007, 09:13 AM

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

This is my favorite. Same engine as our bike, with more leg room and better looks.

Badbob

12-09-2007, 08:39 PM

I saw some of these when I was looking but I could not find a good photo.

Nice.

Regular Guy

12-13-2007, 09:11 PM

I bought my 16 tooth sproket from http://www.rebelgears.com about twenty something bucks, perfect fit, great guys to deal with. They cut many of their own gears in house. Amazing--- a made in America manufacturer. I think they are in Tenn. Guys. try to buy American if possible, for our kid's sake.

A thought about the mileage and speed dilema. I am curious are the ones that get the 70-80 mpg the same ones that only go 60 mph? Mine got 70-77 mpg and only 62 mph before I did mods to carb, exhaust, 16 tooth sproket, plus windshield. Now, on a good day I can do 75-80 (once got to 82 mph) and I weigh 250 lbs.and have a giant box mounted to the back of mine but mileage is now 58-62 mpg. Some days I can only do 60-65 mph. No matter what you do, this bike is still severly limited in the torque department. Things like head wind, tire pressure, hills, weight air temperature and humidity all still exert a large imapct on performance. as for me, I gladly traded 10-15 mpg for 10-15 mph. In my case, the bike was dramaticly better/safer for merging into traffic after the mods., I'm no expert, but I've riden all my life. on 50cc to 1100 cc, two cycle and four cycle. It's not a v-max or 750 Kaw 2-stroker for sure, but it is good at what it was designed to be, a low cost, low maintenance, inner-city, short haul commuter, that said, let's all keep tweaking, you can enhance the performance of this little bike. Don't give up! Your a great bunch and you all try to help one another, I really like that about this group!

Ride Safe!

jonathan180iq

12-14-2007, 01:24 PM

On my 300 mile trip with the 16T sprocket, I had to really goose the throttle in order to keep the speed in 5th gear where I wanted. In doing so, I was using more gas than normal, which, of course, leads to a decrease in fuel economy.

The comparable mileage of any machine differs greatly depending on many factors, including those mentioned by Regular Guy.
And, while this machine can be tweaked, the potentional simply isn't there to make this bike something that it's not, naturally aspirated that is.

Even with improved carb tuning and sprocket variations, this single cylinder 250 4 stroke will always be a simple, lower speed commuter bike.

Now, that being said, there is nothing wrong with that. It's all relative anyway.

This 400 pound 1/4 litre bike that only costs $3,000 isn't that much slower than the 1,000 pound 1100cc $10,000 bike.
Sure, you can't open 'er up on the freeway and get up to 100mph, but how often does the 1100cc guy do that anyway?

In traffic and getting from place to place, we're all going the same speed.
This bike just gets you there cheaper and more efficiently.

For what it's worth and aside from what shortcomings it has, this is the second most efficient bike on the mass market; the first being Kawasaki's 125cc, at around 90mpg.

jonathan180iq

12-14-2007, 01:32 PM

The sweet spot for getting the most miles out of each gallon is probably around 55-60 mph.

Slower than that, and you aren't traveling as far as you could on the same amount of gas.
Faster than that and you are using more gas than necessary to travel said distance.

I haven't tested it, as I ride more often is slow-n-go traffic.

If you wanted to, you could empty your tank completely and pour in 1/4 of a gallon. (carry some spare gas on the rear)
Then, reset your tripometer and ride at 55mph without varying too much, in the reserve position, until the bike stops. Then, take the number of miles traveled and multiply them times 4. That would give you a baseline MPG for 55mph. From there, you would repeat the test at varying speeds to see which average speed is the most efficient.

If no one is following you or if you don't have some spare gas, you'll be SOL when the bike stops. So, make you sure you have some back-up gasoline.

Easy Rider

12-14-2007, 07:00 PM

This 400 pound 1/4 litre bike that only costs $3,000 isn't that much slower than the 1,000 pound 1100cc $10,000 bike.

How many accessories DO you have on that little beast? I thought the advertised dry weight was about 310. :??:

Easy Rider

12-14-2007, 07:03 PM

On my 300 mile trip with the 16T sprocket, I had to really goose the throttle in order to keep the speed in 5th gear where I wanted.

Yea, I can see we need to give you some training on the pleasures of 2-lane country roads. :2tup:

jonathan180iq

12-15-2007, 04:07 PM

I was exaggerating the weight thing for effect. Add a rider and you're looking at a 500 pound machine. For the record, you'd be hard pressed to find a 1,000 pound motorcycle.

Well, 4th gear at 65 is only fun for so long. On the interstate, it just won't cut it. Your feet start going numb from the vibration.

Regular Guy

12-15-2007, 09:00 PM

If you want to see some examples of how efficient a motorcycle can be check out Craig Vetter's Website( he's the guy that invented fairings (windjammers), among other things) @ http://www.craigvetter.com. He ran a contest for a few years and one contestant got 470 mpg. If you want you can make one yourself, he sells kits and instructions for the mod. I suspect these are not very practical on the street, but they are interesting to look at.

One thought I had to mention was if your bike won't go past 60 mph, you might want to check the valve clearances/adjustment. Being over zealous once, I adjusted my valves too tight and they weren't sealing quite all the way on the combustion stroke, not enough to cause a backfire, but enough to rob most of what little power I had. It ran like a dog, a slow dog, maybe more like a dog with a hurt leg. I loosened up on them a bit and bingo the lost power came right back. Just something to look out for!

Easy Rider

12-16-2007, 12:37 PM

Well, 4th gear at 65 is only fun for so long. On the interstate, it just won't cut it. Your feet start going numb from the vibration.

Yes and.........??

That kinda was my point. If you do much Interstate riding, any 250cc bike it probably not the best choice.
As great as the GZ IS, it's not perfect for everything. :tup:

Easy Rider

12-16-2007, 12:43 PM

One thought I had to mention was if your bike won't go past 60 mph, you might want to check the valve clearances/adjustment.

Experience is the best teacher. Good information........especially for a GZ that is still stock. Some folks also notice that the exhaust pipe is getting WAY hotter than normal.

Don't think this applies to those of us who have added 1 tooth to the front sprocket, however. It's doubtful that ALL of us have the valves set too tight! :)