Cut my chain??!

[jenndiggity]

Has anyone changed out your Wheel sprocket to smaller teeth for more low end torque? I heard I need to cut the chain and it will make it noisy???

[Alex]

Plenty of people have made various sprocket swaps. Here's the first DIY that pops up:

http://www.ninjette.org/forums/showthread.php?t=10273

The most common switch seems to be going slightly taller gearing, either changing the front sprocket to a 15-tooth (from stock 14), or lowering the rear from the stock 45-tooth to a 42 or a 43. Going in that direction lowers revs slightly for a given road speed, making the bike a little less "busy-feeling" on the highway. But it would lower effective torque at the same road speed.

Going in the other direction to make the gearing shorter is a bit rarer, though some have done it. This could help the feeling of torque pulling from a stop, but would cause the bike to be running higher revs while cruising. For what it's worth, one of the folks that went to a very tall ratio (15 front / 41 rear), found that gave him the best quarter mile acceleration, so the results aren't immediately intuitive with our bike. To figure out how the revs would actually change depending on gearing, this site is quite helpful to play around with: www.gearingcommander.com

With any of these, if you're only adding a tooth or two, it's unlikely the chain would have to be shortened or lengthened; the stock chain would still work fine.

[alex.s]

Originally Posted by Alex

For what it's worth, one of the folks that went to a very tall ratio (15 front / 41 rear), found that gave him the best quarter mile acceleration

waaaaahhhh????


who is this. i have questions for them.

[flynjay]

Originally Posted by alex.s

waaaaahhhh????


who is this. i have questions for them.

I believe it would be the difference between shifting once and shifting twice.

If you slipped the clutch significantly on take-off, you could get over the initial torque hump to get to a higher 1/4.

[Alex]

Originally Posted by alex.s

waaaaahhhh????


who is this. i have questions for them.

Sorry - I was wrong; he was running 14/41, not 15/41: link

[Alex]

Also - good wiki entry on sprockets:

http://www.ninjette.org/wiki/Should_...ocket_sizes%3F

[alex.s]

oh!... ok.

i'm guessing his 60-80 time was somewhere in the dirt with that configuration?

[alex.s]

that makes me wonder if you went to like 14/50 and started in second if you could get decent starts... i wonder how much the reduced rotating mass adds on smaller sprocket setups like a 13/40. increased sprocket wear for sure

[choneofakind]

Originally Posted by Alex

Sorry - I was wrong; he was running 14/41, not 15/41: link

I actually did notice this phenominon when doing 0-60 runs. I had 14/47 gearing at the time. While each gear was individually quicker, I had to throw in an extra shift to hit 60, but the launch with 14/47 was not any faster than the launch with 14/45. After riding 15/45 for a while, i feel just as quick to 60, but less quick when rolling on in high gears. Unfortunately my camera is broken and any actual evidence of this is going to have to wait till next season when i have a gopro.

It also shifted around my power band (the efi did this in part as well) so I can actually hit an indicated 105 pulling hard at the top of 5th with a shift to 6th still possible, which would put me back in the power band for more. I ran out of road at that point though... The difference is at the track with 14/47, i was hitting a wall at 13.5ish at an indicated 112ish.
Posted via Mobile Device

[Alex]

Originally Posted by alex.s

i wonder how much the reduced rotating mass adds on smaller sprocket setups like a 13/40. increased sprocket wear for sure

The rotating mass argument when applied to sprockets is poppycock. The difference in weight from a 13 tooth to 17 tooth, or a 40 tooth to 50 tooth, is almost inconsequential, and the overall weight of the sprocket is a rounding error when you look at it as compared to the wheel and tire assembly. Not to mention that the sprocket is at the very center of the rotating assembly, making its relatively small weight have very little effect on rotating inertia anyway.

The change in performance due to sprocket changes is overwhelmingly due to the difference in the gearing itself, allowing the engine to apply more force over the appropriate time that it is needed.

[rojoracing53]

I'm running a 15-42 with a 150/60 rear to keep the revs low on the hwy. not sure what my 0-60 time is, after all bragging about how fast my 250 is seem kind of pointless. Throughing around 0-60 times also seems odd since I'm sure there is a huge fluctuation in riders ability to launch the bike even at the semipro racer level.

[rojoracing53]

I think my KOSO Instrument panel has a 0-60 Timer built in, I could give that a test and let you know.

[Jiggles]

Originally Posted by rojoracing53

I'm running a 15-42 with a 150/60 rear to keep the revs low on the hwy. not sure what my 0-60 time is, after all bragging about how fast my 250 is seem kind of pointless. Throughing around 0-60 times also seems odd since I'm sure there is a huge fluctuation in riders ability to launch the bike even at the semipro racer level.

But my 250 IS faster than your 250!

[alex.s]

Originally Posted by Alex

The rotating mass argument when applied to sprockets is poppycock. The difference in weight from a 13 tooth to 17 tooth, or a 40 tooth to 50 tooth, is almost inconsequential, and the overall weight of the sprocket is a rounding error when you look at it as compared to the wheel and tire assembly. Not to mention that the sprocket is at the very center of the rotating assembly, making its relatively small weight have very little effect on rotating inertia anyway.

The change in performance due to sprocket changes is overwhelmingly due to the difference in the gearing itself, allowing the engine to apply more force over the appropriate time that it is needed.

damn, why you gotta twist peoples arms with your fancy "logic"

[Alex]

[alex.s]

cheater.

[choneofakind]

Originally Posted by rojoracing53

I'm running a 15-42 with a 150/60 rear to keep the revs low on the hwy. not sure what my 0-60 time is, after all bragging about how fast my 250 is seem kind of pointless. Throughing around 0-60 times also seems odd since I'm sure there is a huge fluctuation in riders ability to launch the bike even at the semipro racer level.

yes, that's what we've concluded; the launch is a huge part of it, just like with any car/bike. Does that make it useless to compare 0-60 times in cars as well? No, because it quantifies what the vehicle is capable of for comparison purposes. Its also a good way to have a friendly competition that everyone can take part in and learn from while having a little fun on their ninjette.

Its no more pointless to compare acceleration to 60 than it is to raise your gearing so far that you're running twisties in 1st or 2nd. We just have a different idea of what we want from the bike that's all. If I was doing longer distances on the highway, I would be running 15/43 instead of 15/45 to keep the rpms lower to haul comfortably at 75. But I don't, so I have some fun with acceleration and enjoy my bike the way it is.
Posted via Mobile Device

[rojoracing53]

Originally Posted by choneofakind

yes, that's what we've concluded; the launch is a huge part of it, just like with any car/bike. Does that make it useless to compare 0-60 times in cars as well? No, because it quantifies what the vehicle is capable of for comparison purposes. Its also a good way to have a friendly competition that everyone can take part in and learn from while having a little fun on their ninjette.

Its no more pointless to compare acceleration to 60 than it is to raise your gearing so far that you're running twisties in 1st or 2nd. We just have a different idea of what we want from the bike that's all. If I was doing longer distances on the highway, I would be running 15/43 instead of 15/45 to keep the rpms lower to haul comfortably at 75. But I don't, so I have some fun with acceleration and enjoy my bike the way it is.
Posted via Mobile Device

I'm not dissing the comparison of 0-60 times with any seriousness that's just my sense of humor
As far a the importance of launching, just thinking about it makes me smile because I can't help but think back to when we'd show up to regional race event(AFM, WSMC, WERA) and there'd be guys taking the holeshot from the fifth row.

Not to ignore the original topic but when I bought my bike the guy had be running a 14-42 with 104 links and it was all the way to the front of the swingarm slots. I can't wait to wear out this current chain and get back to 106 with a bit of adjustability.