Gearing question

[abacall]

I'm looking to get some shorter gearing for the bike, and trying to get some options. I don't really want to go with the full 520 -1/+2 conversion as I still tour a good amount in the summer.
I need some clarification on the whole gearing issue.
I understand the benefits of less rotational mass. I understand shorter gearing also, and I think the Fizzer can stand some shorter gearing.
At the same time, I don't want to be spinning 10K while cruising on the highway.
Any input is appreciated as I'm pretty clueless when it comes to gearing.

Also, does replacing sprockets necessitate a new chain?

 

[OZXJR]

I.ve got a 15 t ready to go on mine ,just waiting for a s/healer.I will be interested to see what effect it has and no,you don't need a new chain if you are just swapping out the front sprocket.

 

[Hollywood416]

I was in the same situation I do alot of touring and highway riding so I went with the -1 front leaving everything else alone and it is great. Turns about 6k@65, 7k@75 etc in 6th and gave me a good bit more low end torque. A little buzzier on the highway but no issues.

 

[abacall]

Anyone else care to chime in?

 

[Wolfman]

I had the -1 530n sprocket on my FZ6...definitely an improvement, and nowhere near as radical as the 520 conversion, -1, +2 combo...

But i would say, that you could even go -1 at the front & +1 rear in a 530, and it would be a little better again for pick up, without being too silly in the revs department....dont know the math, but i am sure someone here does, would be interesting to know how that combo would work....cant recall reading in here, where anyone has got -1, +1 530 combination...

:thumbup:

 

[abacall]

I will be interested to see what effect it has and no,you don't need a new chain if you are just swapping out the front sprocket.

Do I need a new chain when changing the rear sprocket?

What's the service interval on the Vortex AL one?

 

[Oscar54]

You can determine what your rpm will be at depending on the changes you make in the final drive configuration by knowing that the diameter of your rear wheel is 24.84 inches for a 180/55-17 Dunlop. This equates to circumference of 78.04 inches. Therefore your rear wheel has to turn 812 times to move 1 mile. (5,280' X 12" / 78.04" = 812 revolutions.

The formula to use is Engine RPM = primary reduction ratio (1.955) X 6th gear reduction ratio (1.083) X final drive reduction ratio (46/16 or 2.875) X rear wheel RPM.

Since the rear wheel must turn 812 times to cover 1 mile, then at 60 miles per hour the rear wheel must turn 812 times in one minute.

Therefore, the RPM at 60 MPH is 1.955 X 1.083 X 2.875 X 812 = 4,942 RPM.

So now just change the final reduction ratio and you can determine your RPM.

Wheel RPM at 70 MPH is 70 / 60 X 812 = 950 RPM. etc.

Hope this helps.

 

[abacall]

Excellent information, very helpful. Repped.
So, the only variable that will change will be the final drive reduction ratio. Therefore changing it from 46/16 to 47/15 or 3.133.
That would mean with a -1/+1 change I should be spinning 5,386 RPM. Or a +444 RPM change at 60 mph.
At a more reasonable 75 mph I should be spinning 6,733 RPM, where stock it would be 6,178 RPM. A difference of +555 at 75 MPH.
I can live with that.


How about the chain?

 

[Oscar54]

Excellent information, very helpful. Repped.

How about the chain?

I bought a new 520 43t rear sprocket on ebay for $12 and when my stock chain spec's out I think i will go with the 520 chain conversion. Its cheaper and should be lighter? I'm thinking of staying at +1 up front with the -3 on the back for a 2.53 final. I want better mileage since I commute 100 mile round trip.

So, since you should use a new chain on new sprockets generally, I guess if I were going to change my sprockets I would convert to the 520.

Anyway enjoy your experiment. I hope it gives you the performance you are looking for.

 

[Hollywood416]

Excellent information, very helpful. Repped.
So, the only variable that will change will be the final drive reduction ratio. Therefore changing it from 46/16 to 47/15 or 3.133.
That would mean with a -1/+1 change I should be spinning 5,386 RPM. Or a +444 RPM change at 60 mph.
At a more reasonable 75 mph I should be spinning 6,733 RPM, where stock it would be 6,178 RPM. A difference of +555 at 75 MPH.
I can live with that.


How about the chain?

Something is off about that calculation.. not sure what but I know for fact mine turns almost exactly 7k rpm's at 75 with just the -1 front. Just wouldn't want you making a decision off sqewed info. :thumbup: Maxes out 147 at rev limiter(14k) on the dyno.

 

[abacall]

Ok, so here's another question.... What are the downsides of a 520 conversion?

 

[Doorag]

There's a huge thread on this already. Try using the search.

 

[Oscar54]

Something is off about that calculation.. not sure what but I know for fact mine turns almost exactly 7k rpm's at 75 with just the -1 front. Just wouldn't want you making a decision off sqewed info. :thumbup: Maxes out 147 at rev limiter(14k) on the dyno.

The formula is correct.

For instance with my stock gearing at 46/16, my tachometer read 5,770 RPM when the speedometer read 70MPH, the formula above calculates 5,766 RPM. I think that is pretty close? So, in abacall’s case, if he goes -1, +1, his final drive ratio goes to 3.133. So at 5,770 RPM he is actually going 64 MPH but his speedometer will read 70MPH.

Also, the speedometer is driven off the RPM of the output drive shaft as read by the sensor. So it does not matter what you do to your final drive ratio, it has no affect on what you read on your instruments. Yamaha calibrated your speedometer based on a fixed 2.875 final drive ratio and stock tire diameter.

Therefore, if you change the final drive ratio or tire size it has no affect on the reading on your speedometer for a given engine RPM.

I don’t know if you have done anything to your speedometer like the speedohealer. But, if you are getting the readings you say, you may want to check the calibration on your speedometer. Your speedometer should read around 85 MPH for 7K RPM unless you changed the calibration. The formula for your final drive ratio of 3.067 gives a speed of 79.65 MPH at 7K.

 

[Oscar54]

Ok, so here's another question.... What are the downsides of a 520 conversion?

Other than cost, you have to make sure the chain you get is of high enough quality to run on a 750 to 1000cc bike.

So if you get quality sprockets and chain, there should be no downside I can see.

 

[Oscar54]

There's a huge thread on this already. Try using the search.

You are correct sir.

but that is not as much fun!

There are threads of old football games, but people still like to talk about them!

 

[abacall]

Oscar's the man. Thanks again for all your input. I think I'm going to wait a bit and get the 520 conversion with -1/+1. Seems to be a good combination for my intended outcome.

 

[abacall]

There's a huge thread on this already. Try using the search.

You're right. And I did read as much as I could. But there is so much, and it's become so cluttered that it becomes extremely difficult to find the information I'm looking for.
So, thanks for humoring me everyone. :cheer:

 

[Hollywood416]

The formula is correct.

For instance with my stock gearing at 46/16, my tachometer read 5,770 RPM when the speedometer read 70MPH, the formula above calculates 5,766 RPM. I think that is pretty close? So, in abacall’s case, if he goes -1, +1, his final drive ratio goes to 3.133. So at 5,770 RPM he is actually going 64 MPH but his speedometer will read 70MPH.

Also, the speedometer is driven off the RPM of the output drive shaft as read by the sensor. So it does not matter what you do to your final drive ratio, it has no affect on what you read on your instruments. Yamaha calibrated your speedometer based on a fixed 2.875 final drive ratio and stock tire diameter.

Therefore, if you change the final drive ratio or tire size it has no affect on the reading on your speedometer for a given engine RPM.

I don’t know if you have done anything to your speedometer like the speedohealer. But, if you are getting the readings you say, you may want to check the calibration on your speedometer. Your speedometer should read around 85 MPH for 7K RPM unless you changed the calibration. The formula for your final drive ratio of 3.067 gives a speed of 79.65 MPH at 7K.

They shouldn't effect the Tack but they do majorly effect the speedo. Based on that fixed calibration when you change the gearing the engine is turning the same RPM but the tire is turning a different speed for that given RPM.
The speedo would have read about 85mph for 7k in stock form but that was way off. With my changes my speedo was off by 11.6% across the board about 5.5% from the factory and another 5 becasue of the 15/46 gearing. The calculations seem to be off about as much as the factory speedo is which may be the reason for the discrepency in MPH the factory sets them up to read about 5mph fast across the board so the input final drive ratio number may be sqewed and not 100%.
I seem to remember someone else posting a false reading off one of those gearing calulators a while back could be wrong about that but I know mine are 100% correct. I have the speedohealer and my MPH is GPS verified as well as I checked my last Dyno sheet and the MPH/RPM were both the same on there as well which takes out the variables of a problem with the factory settings.
:thumbup:

 

[yamaha rider87]

Do I need a new chain when changing the rear sprocket?

What's the service interval on the Vortex AL one?

You will not NEED to change the chain however I would strongly recommend it so that your new sprockets and new chain are starting their wear cycles at the same point, that way you can change them all as a set instead of having to remember when you have to change what, and the service interval on the Vortex sprockets seems to be between 5-6,000 miles according to guys who posted in my thread about this. I just installed a -1 +2 and had the same concerns as you, but I make it down the freeway at 85 running about 8,000rpms in 6th, which fine for me, but if you don't like your engine spinning that high you can always go with the -1/+1 that wolfman was talking about, as I am sure that would take some stress off the engine at those higher speeds. Gotta tell you though, having done the swap and feeling the difference in pick-up, I will NEVER go back to the stock 16/46 or anything less radical then what I have now. In fact next time I might do Wolfman's -2 front +1 rear and add even more torque to the low end of the powerband!

 

[kdbaum125]

If you search for motorcycle gearing calculator you can find some useful tools in gearing and chain modification.

Gearing Commander: Motorcycle Gearing Ratio Sprocket RPM Speed Chain Calculator