Ninja throwing star sprocket?

[jezebel]

So today we were joking that if my ninja was black I should get leathers that looked like a ninja costume, katana-looking handlebar grips.. and ninja throwingstar sprockets..

I looked, and.. yeah - I kinda want them!

http://cgi.ebay.ca/VORTEX-CAT5-REAR-...#ht_2853wt_905

[Snake]

That would look totaly cool on any color Ninjette. Great find.

[greatwhiteninja]

the white SE ninjas actually have a little ninja guy throwing stars.. its in the black part of the graphics.. didnt even notice it at first until i peeled them off and was up close on them..lol! actually all over the side fairing vinyl and near the rear seat has little throwing stars very faint like shadows.. kinda cool.

[kkim]

is that made from aluminum? if so, I wouldn't recommend them.

[greatwhiteninja]

they say it is.. Made from 7075 T6 aluminum

[rusninja]

because aluminum wears quick? if so how long you think?

[Alex]

It varies. But significantly quicker than steel sprockets.

[rusninja]

do they make steel colored sprockets :O

[CThunder-blue]

That's a 47T sprocket

[rusninja]

man we need a 60t poping wheelies all day x] jk XD

[CZroe]

Uhh... that looks more like a saw blade.

[jezebel]

so 47t is bad?

And maybe a saw blade, but to me it looks like a throwing star

[CThunder-blue]

47T will increase acceleration but reduce how much top speed you get. Generally speaking, people go lower than the stock 45, not higher. You can use http://www.gearingcommander.com/ to figure out what speed you would be at with what kind of gear combo. The ninja 250 is in the database so just use the menu to select it and you can play around with it.

[jezebel]

Originally Posted by CThunder-blue

47T will increase acceleration but reduce how much top speed you get. Generally speaking, people go lower than the stock 45, not higher. You can use http://www.gearingcommander.com/ to figure out what speed you would be at with what kind of gear combo. The ninja 250 is in the database so just use the menu to select it and you can play around with it.

Dude you're a wealth of knowledge! Thanks!
That site is pretty cool, though I'm not sure I understand it. I think if I read right, if I went with a 17/42 setup, I could hit a top speed of over 200km/h - but I don't see anywhere that it refers to accelleration affects... any ideas?

[CZroe]

While it will increase the speed at a given RPM, it doesn't actually increase your top speed unless you were rev-limited (on a Ninjette, you weren't). Same HP vs. Wind resistance = about the same top speed

Now, a 16 tooth front sprocket requires you to modify the sprocket cover. A 17 tooth might not be easily possible. Taking the rear down to 39 would have about the same effect as that extra front tooth, so 16:39 is possible.

[CThunder-blue]

Originally Posted by jezebel

Dude you're a wealth of knowledge! Thanks!
That site is pretty cool, though I'm not sure I understand it. I think if I read right, if I went with a 17/42 setup, I could hit a top speed of over 200km/h - but I don't see anywhere that it refers to accelleration affects... any ideas?

You can generally gauge the acceleration affects by the first few numbers in the first gear category. When the number goes up, your acceleration will decrease. When it goes down, acceleration will increase. Just keep in mind that you also want to keep track of your cruising RPM in 6th gear. I find that website is pretty accurate in it's calculations.

Here's an example:
stock gearing/ sprockets


15/45 sprockets: Notice the numbers- the speed in MPH- goes up in relation to the RPM? Since the Final Drive Ratio is now taller, the speed is now higher at a given RPM. However, what this means is that it takes longer to reach that speed.


13/45 sprockets: Conversely, lowering the number means you will accelerate faster, but lose the top speed in 6th gear. Notice how in the stock 14/45 setup at 12.3K RPM the speed is maxed out at 99.8, but with a 13/45 setup at 12.3K RPM the speed would be maxed out at 92.7.


Hope that helps

[CZroe]

Originally Posted by CThunder-blue

...
13/45 sprockets: Conversely, lowering the number means you will accelerate faster, but lose the top speed in 6th gear. Notice how in the stock 14/45 setup at 12.3K RPM the speed is maxed out at 99.8, but with a 13/45 setup at 12.3K RPM the speed would be maxed out at 92.7.

Just to clarify, since the rev limiter isn't set to 12.3K RPM (doesn't even redline until 13K), the bike's top speed is not increased, just the speed at that given RPM. Basically, the top RPM attainable with the taller front gear is now lower because the wind resistance will overcome the HP sooner. Ultimately, you will reach the same top speed at a lower RPM.

[CThunder-blue]

Originally Posted by CZroe

Just to clarify, since the rev limiter isn't set to 12.3K RPM (doesn't even redline until 13K), the bike's top speed is not increased, just the speed at that given RPM. Basically, the top RPM attainable with the taller front gear is now lower because the wind resistance will overcome the HP sooner. Ultimately, you will reach the same top speed at a lower RPM.

I think your explanation was more confusing than mine. LOL. However, theoretically, with the taller gear, the top speed does increase if you have enough HP to push it. I didn't want to mix in HP into the explanation since she was only asking how gearing relates to acceleration. To me, it's just easier using the larger numbers to show how different the Final drive becomes.

Sorry to derail the thread though.

[CZroe]

Originally Posted by CThunder-blue

I think your explanation was more confusing than mine. LOL. However, theoretically, with the taller gear, the top speed does increase if you have enough HP to push it. I didn't want to mix in HP into the explanation since she was only asking how gearing relates to acceleration. To me, it's just easier using the larger numbers to show how different the Final drive becomes.

ONLY if you had enough HP to hit the rev limiter in top gear before the gearing change. Without the rev limiter artificially limiting the top speed prior to a gearing change, it has the same top speed as determined by HP vs. wind resistance... you will just be running lower RPM when you hit it and the engine will not be capable of hitting the same RPMs it hit prior to the gearing change.

[jezebel]

wow you guys know your stuff -
so if I understand, I can't increase my top speed because even if the sprockets would theoretically allow for it (understanding a decrease in acceleration), the bike doesn't have the HP to get there? is that right?

I really should write a post about this on my site - just not sure I get it yet :P

[CThunder-blue]

Every bike and rider is different. For instance my bike has jetted carbs, shimmed needles, brt tis ignition, and a 15/43 combo. I've never tried to hit top speed because it's pretty fast. I can do 80mph in 6th at only 9k and the bike still feels like it can go faster. I believe that the bike could max out the speed at over 100. I know I hit 90 on it once with the stock sprockets and it was still pulling when I let off the throttle. I wouldn't write off the ninjette as not having enough hp to increase your speed.

[Alex]

Originally Posted by jezebel

so if I understand, I can't increase my top speed because even if the sprockets would theoretically allow for it (understanding a decrease in acceleration), the bike doesn't have the HP to get there? is that right?

Pretty much. If the bike was capable of hitting the redline (max speed for engine) in top gear, then by making the gear ratios taller, the top speed would increase right up until the point the bike hit redline once again, or it didn't have enough hp to pull the bike any faster through the air.

Since we already hit that equilibrium in top gear and can't pull to redline (assuming a reasonably stock bike and stock gears), changing to taller gear doesn't improve top speed much at all, if any.

With most motorcycles, people make the gearing shorter to improve acceleration. A typical sportbike gearing, has it hitting redline in top gear at 170+ mph+ for a 600 and 190+ mph for a 1000, though they are often electronically limited to 186 mph anyway. By making the gearing shorter (smaller front sprocket and/or larger rear sprocket), it improves the acceleration of the bike in real-world conditions, and while top speed is affected, nobody needs to go 160+ on the public roads anyway.

The ninjette is a special case with our tremendously short gearing already, so people often go the other direction and make it taller (larger front sprocket and/or smaller rear sprocket), which lowers the revs at a given road speed, and making things slightly calmer on the highway.

[Lowspeed Lowside]

One thing to keep in mind is that it is beneficial to choose sprockets and a chain length with a coprime number of teeth/links with the idea to spread wear the most evenly.

[CZroe]

The rev limiter is actually a bit past redline (14K, IIRC. redlines at 13K) but you may be looking at redline for top sustainable/safe cruising speed. Because it increases your speed for a given RPM, it does increase the speed that you can reach while staying under redline. You kinda have to be going downhill and 105+MPH indicated to do that with stock gearing and that's about the top speed regardless of gearing anyway. I routinely see almost 110 indicated (~100MPH actual) when going downhill with 15:41 and I'd probably be in the red at 14:45 but, as long as it doesn't require over 14K RPM, it can do it at any gear ratio.

[Alex]

Good point, redline doesn't necessarily equal rev limiter.