Changing Rear Sprocket 4 Teeth Lesser

[Cobrabiker]

Hi, I have a 1000cc FZ1, it is running 120 km/hr at 5000 rpm on 6th gear, I am thinking of changing the rear sprocket (as it is easier than the front according to the mechanic), from 44 teeth to 40 teeth, and was wondering how much rpm it will lower from the change?

[neverdie]

Easy.

Using a age old method, that I have used thousands of times I calculate the following. I can let you in on my secret later, after you asked me, "How the F did you do that neverdie" question.

Firstly tho, you have neglected to tell me the year model of your FZ, I thought from memory they came with a 45 rear tooth sprocket standard?? And thus with that, your actual speed at 5000 RPM is actually 121.2km/h.

Anyway, simply dropping from the 45 to a 40 would do this at 5000 RPM....would increase the speed to 136.3km/h.

If your FZ is actually running a 44 at the rear, ur real speed at 5000RPM is 123.9km/h.

hope this helps

cheers

Edited January 12, 2010 by neverdie

[SeanMoran]

Ten percent quicker with ten percent less torque. I did the same a few weeks ago with my Honda, but swapped a 44 tooth rear sprocket for a 36, and she's still got plenty of power to get a 75kg man off the mark, but surely does fly with 20% more velocity for the same revs.

I'm not interested in drag racing, and she's still quick enough over the quarter mile, but the revs are not so exasperating.

[neverdie]

I think ive just answered my own question above, ur running a 04 model? y/n?

they had a 44 tooth rear sprocket and a 11,500 red line, y/n?

[neverdie]

So based on that above, if 04 is the correct model at 5000 rpm you are actually doing 122.4km/h in 6th gear.

changing the rear sprocket to 40 tooth, will give you 134.6km/h.

[Fishenough]

Have you tried the variety of gear ratio calculators on the web? From sprocket ratio charts to find your drive ratio, to a gearing calulator used with your gear ratios from your manual entered, in the Excel sheet. Find your speed for each gear at different engine speeds.

Cheers

[Richard-BKK]

Another tool is http://www.gearingcommander.com/, it is very likely where Neverdie get its intelligence from, anyway, websites and calculators like this are only a indication... Most often they are not accurate and sometime even downright wrong.

It's not uncommon that people visit websites or believe recommendations on discussion boards and invest money to order the sprockets to find that the performance is not near what they expected...

[Fishenough]

Another tool is http://www.gearingcommander.com/, it is very likely where Neverdie get its intelligence from, anyway, websites and calculators like this are only a indication... Most often they are not accurate and sometime even downright wrong.

It's not uncommon that people visit websites or believe recommendations on discussion boards and invest money to order the sprockets to find that the performance is not near what they expected...

Uh huh. Had the ones I posted book marked because someone once posted elsewhere that they were confirmed accurate. Uh huh. Well it did seem close enough to what my little Kawasaki reported, is just plain less work than all the manual calculations. Because the one factor in the equations to find speed is the actual outside circumference of the tire, not just 'it's a 17 incher'. On top of that tires grow some circumference at 134.6 km/h, maybe adds 0.1 km/h; hard to tell.

[neverdie]

Another tool is http://www.gearingcommander.com/, it is very likely where Neverdie get its intelligence from, anyway, websites and calculators like this are only a indication... Most often they are not accurate and sometime even downright wrong.

It's not uncommon that people visit websites or believe recommendations on discussion boards and invest money to order the sprockets to find that the performance is not near what they expected...

Ohhh and they would be better off just coming to your website and reading heaps of <deleted> about dodgy little motor scooters imported from the bowels of india.

Ive actually used gearing commander before, one of the more accurate sites for this type of thing, they are a dime a dozen.....its hardly rocket science Richie.

[Cobrabiker]

Hi Neverdie, it is a 2003 model, 16 teeth front and 44 rear, your calculation is right, it is actually running slightly below 5000rmp at 120, so the change will make it at 134km with the same rpm. What about a further 2 teeth, at 38 rear teeth, what kind of speed should I expect at the same rpm?

Is the front more difficult to change than the rear?

Hi SeanMoran, how many cc is the Honda? Wow that is a 8 teeth difference? Do you lose a lot of power for 1st gear acceleration?

[neverdie]

141.7km/h if you go to 38.

No doubt Richard will be along soon to tell me I am wrong again , dispite you confirming my calculations

You may be disappointed if you go too far, sprockets arent that expensive really, maybe try the 40 before you go too much lower.

[neverdie]

Hi Neverdie, it is a 2003 model, 16 teeth front and 44 rear, your calculation is right, it is actually running slightly below 5000rmp at 120, so the change will make it at 134km with the same rpm. What about a further 2 teeth, at 38 rear teeth, what kind of speed should I expect at the same rpm?

Is the front more difficult to change than the rear?

Hi SeanMoran, how many cc is the Honda? Wow that is a 8 teeth difference? Do you lose a lot of power for 1st gear acceleration?

Sorry, I neglected to answer your other question. The rear sprocket is easy to change because you can drop the rear wheel off without pulling the chain apart, but at the end of the day its not that much harder to change the front, some might even argue its easier, depending on the model. You need to pull the chain apart at the joining linkage to do the front sprocket, but you can leave the rear wheel on, theres not that much in it, just depends what you have to remove to get to the front sprocket.

i havent done one on your bike, cant picture it in my empty head but im sure it wouldnt be too hard, do you want to do it yourself or pay someone?

Edited January 12, 2010 by neverdie

[neverdie]

Hi Neverdie, it is a 2003 model, 16 teeth front and 44 rear, your calculation is right, it is actually running slightly below 5000rmp at 120, so the change will make it at 134km with the same rpm. What about a further 2 teeth, at 38 rear teeth, what kind of speed should I expect at the same rpm?

Is the front more difficult to change than the rear?

Hi SeanMoran, how many cc is the Honda? Wow that is a 8 teeth difference? Do you lose a lot of power for 1st gear acceleration?

Have a look at gearingcommander.com (the one richard spoke of), I just compared its figures with my Raider, I just played with sprockets on it and the figures matched exactly with what I achieved on gps.....I wonder how that could be Richard?

[Richard-BKK]

Dear Neverdie,

We hardly report about scooters from India only if there is Thai link, "Motorcycle Thailand" reports mainly about what it says motorcycles in Thailand, but you right ..it's indeed hardly rocket science. Still, would you guarantee your numbers, so if they not correct Cobrabike can claim the cost from you?

The website gearingcommander.com is indeed one of the better once, it's the reason why I introduced it... Still I see websites as this as tools and not as absolute facts... even some numbers can be accurate..

Edited January 12, 2010 by Richard-BKK

[SeanMoran]

Hi SeanMoran, how many cc is the Honda? Wow that is a 8 teeth difference? Do you lose a lot of power for 1st gear acceleration?

Well, if we remember that 4 teeth is precisely 10% of 40 teeth, but NOT 10% of 44 teeth, although close enough as an estimate in realtime when you have traffic and road and tyre air pressure and wrist reflexes and all those things as outliers to the maths, 44-36 means I get roughly 20% higher velocities for the same revs. It's actually 22.222% faster if you take 100 and divide by 36 and multiply by 44.

The torque is correspondingly less but she's a little 125 two-stroke with six gears and a powerband somewhere between 6000-11000 revs by my reckoning, and it's just a matter of finesse to get her off the standing start now that she's 20% faster. It's riding on the road and not competitive drag racing, so I just listen to the revs and change gears when it sounds about the right time for a gear change, remembering that I'm moving at around 20% faster than before, but 125 two-strokes aren't all that interested in low revs.

Essentially, tonking along at walking pace in first gear up a hill is something to pay attention to with the clutch hand ready, but as soon as we're on the highway, that 20% difference is wonderful, great, fantastic, terrific, and probably saves a lot of benzine and wear and tear on the engine while I'm just trying to keep up with the traffic and avoid another collision in the throes of modernday rural Thai commuting between the traffic lights.

There's been nobody (by chance) go anywhere near to catching me off the lights (after cha-cha through the intersection) even with this lesser rear sproket. The range of that powerband means that it's all in the wrist. She's still just as quick as before, but I get the time to take phone calls between gear changes, nothing more.

[neverdie]

Dear Neverdie,

We hardly report about scooters from India only if there is Thai link, "Motorcycle Thailand" reports mainly about what it says motorcycles in Thailand, but you right ..it's indeed hardly rocket science. Still, would you guarantee your numbers, so if they not correct Cobrabike can claim the cost from you?

Yes okay Richard, I will buy Cobrabike some new sprockets if that will keep you happy.....perhaps you might like to do the same guarantee when giving recommendations via your site, perhaps you can refund people money after they proceed to buy a piece of junk on your advice & guidance.

Do I need to provide a disclaimer for Cobrabike on this issue, I havent heard him jumping up and down about it, however since I havent been trying to work out his torque curve & provide him with exact dyno reading for his 2003 model bike, by looking at a deck of cards I am sure what I have said will be acurate to within a poofteenth........IS THAT OKAY WITH YOU COBRABIKE? (I'm guessing Richard wont be happy with it)

[neverdie]

Cobrabike,

please note my new disclaimer in my signature.....there is a chance that I could be wrong, but I bet im not

[Richard-BKK]

Neverdie,

You just so like a kid... grow-up. I will be very happy if the OP is happy with your information.

[Cobrabiker]

I bet down to 38, wheelie will be impossible, thanks for the hard work neverdie, I need some more feed back before I change.

[neverdie]

Neverdie,

You just so like a kid... grow-up. I will be very happy if the OP is happy with your information.

Yes I am ....afterall Im only 14.

I bet down to 38, wheelie will be impossible, thanks for the hard work neverdie, I need some more feed back before I change.

Cobrabiker, mate, people often stuff around with sprockets only to come out disappointed. Yamaha put a fair bit of research into the gearing that drives your bike, when you start to play with that, something generally suffers.

If you can increase the horsepower of the bike, then perhaps your rear sprocket adjustment would be less noticable, but if your running a stock or tired bike, chance are you may not appreciate the changes. If your going to do it, go a little bit at a time, certainly not from 44 down to 38.

Sorry I cant be more help, I havent owned one of ur bikes before & Id like to be the big man and pay for everyones sprockets but as you might appreciate that aint gonna happen.

Now take yourself over to Richards site and enjoy reading his stories on Auto bikes built in Syberia by 3 legged, two headed pigmys

[SeanMoran]

I bet down to 38, wheelie will be impossible, thanks for the hard work neverdie, I need some more feed back before I change.

I can still do the wheelies after 44-->36 because the mass of the bike and rider are just the same and the engine has the same power. It's just that I am doing them 20% faster than before, but this is a little two-stroke bike, totally reliant on that powerband - probably a bit like nitrous' would be like to a four-stroke.

There was twice as much power as I needed to start with, so that's why I went to the trouble of changing to a smaller rear sprocket - still enough power to burn the wick off a cucumber but smoothie smoothe smoother on the highway, and 20% faster for the same revs. She'd still redline in top gear now quite easily if I had the guts to try it. 150km/h in shorts and thongs is quick enough for me to get the white knuckles, and that's at around 9000 rpm with 2000 left and she's raring to try it. I will oneday, but not in casual tourist clobber.

[neverdie]

I bet down to 38, wheelie will be impossible, thanks for the hard work neverdie, I need some more feed back before I change.

I can still do the wheelies after 44-->36 because the mass of the bike and rider are just the same and the engine has the same power. It's just that I am doing them 20% faster than before, but this is a little two-stroke bike, totally reliant on that powerband - probably a bit like nitrous' would be like to a four-stroke.

There was twice as much power as I needed to start with, so that's why I went to the trouble of changing to a smaller rear sprocket - still enough power to burn the wick off a cucumber but smoothie smoothe smoother on the highway, and 20% faster for the same revs. She'd still redline in top gear now quite easily if I had the guts to try it. 150km/h in shorts and thongs is quick enough for me to get the white knuckles, and that's at around 9000 rpm with 2000 left and she's raring to try it. I will oneday, but not in casual tourist clobber.

Can you offer any guarantees with that?

[Richard-BKK]

It's remarkable if you search on Internet for Suzuki Raider 150R which weird motorcycle (build in Syberia by 3 legged, two headed pigmys comes up) http://www.google.com/search?hl=en&sou...oq=&aqi=g10

[SeanMoran]

Can you offer any guarantees with that?

You callin me yeller, punk?

Yeah, I reckon she'll still redline in top gear without any hesitation, but when I get near to that level is when I start to remember that I'm wearing a pair of thongs, shorts and a 300 baht helmet. and it's I who guttoes out and cools off, not the Honda. I have to take off to Cambodia at the end of month and I'll be wearing the jeans and sneakers for that ride, and the rear tyre needs a new tubeless one to stop the cavitation from the tube that's messing up the wheel balance right now, but I'll find the right time and place to break the 180km/h barrier then, and make sure to wear an helmet that doesn't want to fall off the back of my head and strangle me at that speed.

The smaller rear sprocket (on a little 125 two-stoke) has been a good move allround, with no drawbacks at all IMHO, and I guarantee that the extra 30km/h top speed is no problems for the Honda, even with a 10kg rucksack. I weigh around 75kg before breakfast and she has a good enough fairing to hide behind if there's a north-easterly wind blowing that morning. This is a small capacity bike I have here. On a 1000 FZR, these rucksack/wind issues are nothing to fret over.

[Cobrabiker]

Hi Richard, that gearing commander is really helping, I am busily working on the proper gearing. Neverdie, I think I need at least 6 down to 38, the smallest size for the rear for FZ1, need to increase the front from 16 to 17 to get the same effect as Sean. Total will be about 8.5 teeth lesser for rear.

Hi Sean, do you feel a big difference in acceleration on 1st gear from standstill compare to stock? I mean pick up speed? Power loss about 20 % for pickup? And you sure still can wheelie on 1st gear?

[tatt2dude]

Hi Richard, that gearing commander is really helping, I am busily working on the proper gearing. Neverdie, I think I need at least 6 down to 38, the smallest size for the rear for FZ1, need to increase the front from 16 to 17 to get the same effect as Sean. Total will be about 8.5 teeth lesser for rear.

Hi Sean, do you feel a big difference in acceleration on 1st gear from standstill compare to stock? I mean pick up speed? Power loss about 20 % for pickup? And you sure still can wheelie on 1st gear?

Yeah I wouldn't do that if I were you.

In principle you guys are on the same page but you are comparing chalk and cheese in the two bikes. On a two stroke you can make radical gearing changes and find top or bottom end power an 8 tooth change on your FZR could make it a pig. What exactly are you trying to achieve? 8 teeth down will give you more top end but it will take forever to get there.

My advice would be to change the front sprocket first, no need to split the chain. If you have enough play in the chain then you wont even need to take the wheel off. What you need to do: Get your fatest mate sat on the bike with front and back brake on (maybe bike in gear, cant remember its been so long!) you will need a torque wrench and socket or a scaffold pole for leverage. Crack the nut on the front sprocket first with fat mate in place. Once the nut is cracked get her up on a paddock stand and loosen off the chain adjusters and rear spindle, here you will find if you have enough play to remove chain from front sprocket, if not drop the back wheel out it's a 10 minute job. Change sprocket reverse process to tighten.

Go one up on the front (=2.5 down on the back) this will give you a very noticeable difference in power delivery and top end. If she is still not bouncy enough for you at the top end then start changing the back sprocket, I would say no more than one tooth at a time until you get what you desire.

Am I right in thinking the FZR has the same lump as the 04 R1 (bottom end)?

Gearing from a website? Well I never what next? I spent a number or years racing big bikes, the last year in superstocks. Set up is a very personal thing, although a gearing chart gives info it does not take into consideration an important part of the motorcycle........ YOU! How you ride the bike will determine what gearing you need and it is very much a step by step process to find out what is right for you, never make radical changes to the set up, tip toe your progress.

Go down one on the front, it will take you in the right direction and then you can fine tune the rear.

I raced GSXR100'S for three years, we never went more than four teeth from standard even for Snetterton (175mph back straight). With these modern big engines it's all about torque, so gearing changes can have massive impact on how the bike rides.

Btw: If you go down 8 teeth you will need to split the chain and take a link or two out.

[Cobrabiker]

What about the chain? Do have to change it if I change from 44 to 38 teeth rear sprocket?

[tatt2dude]

Another tool is http://www.gearingcommander.com/, it is very likely where Neverdie get its intelligence from, anyway, websites and calculators like this are only a indication... Most often they are not accurate and sometime even downright wrong.

It's not uncommon that people visit websites or believe recommendations on discussion boards and invest money to order the sprockets to find that the performance is not near what they expected...

Exactly! Good advice.

In 04 I had two Suzuki GSXR1000K3, from memory (which is not great) I think Suzuki stated 160bhp at the crank. Straight as we got the bikes they went on a dyno before getting stripped. Neither made 160bhp and one was 8bhp up on the other. So in theory if I had used the gearing calculator on those two bikes in stock trim I would have had two very different power deliveries from the same model motorcycle.

Stuff like that is for guide only, gives you a starting point. I am amazed people are handing out the info as if it is knowledge or experience.

[tatt2dude]

What about the chain? Do have to change it if I change from 44 to 38 teeth rear sprocket?

Yes your going to more than likely have to split it and drop a link out. It's not difficult to do just arse ache. You may get away with a split pin link in the chain if you are going the top end direction, although you should really stick to a riveted link on a thou.

If you are going that direction then switch to race sprockets and run a 520 chain, have a look at renthal's they make pucker sprockets.

It keeps you standard chain etc exactly that as a spare. And should you find you don't like your new gearing (which I don't think you will) then you can at least change straight back to standard with no extra cost.

Seriously dude: Don't go 8 teeth.

[VocalNeal]

I changed from a 42 to a 40 on my bike to take advantage of extra power and primarily to improve mid range 'cruising" during a commute. It works fine for that. But it is a little slower off the line but only for the first 10m.

I do notice however that at my level of riding when I am in Khao Yai that in some slow corners I am in between gears. Too slow for 2nd too fast for 1st. But then I still get passed on the straights.

Edited January 13, 2010 by VocalNeal