Looking for feedback on 15/45 sprockets on a 919 - Wrist Twisters
 
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post #1 of 14 Old 06-26-2008, 11:52 AM Thread Starter
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Looking for feedback on 15/45 sprockets on a 919

I'm looking to pick up a little straight line acceleration from my 9'er and am considering going to a 15/45 sprocket setup. Does anyone with this setup have any feedback? Was the acceleraton increase quite noticeable? How did things change at cruising speed on the highway?

'02 919
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post #2 of 14 Old 06-26-2008, 01:24 PM
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Reportedly, while the 15/45 combination has a high "WAHOO!!" factor, the front end is very difficult to keep on the ground in the lower gears so it's overall acceleration is slower due to having to carefully feather the throttle.

As for highway cruise, with stock gearing 75 mph is 4700 rpm, but with the 15/45 it's 5260 -- a significant jump.

For "a little" more acceleration you might try a 15 tooth countershaft sprocket with the stock rear for a ratio of 2.867:1 -- almost right between the 15/45 and stock. Plus, if you have 112 links in the chain, it would probably not need to be shortened.

Rob

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On the other hand, if it has not been done never assume it is impossible to do it.
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post #3 of 14 Old 06-26-2008, 01:31 PM
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thats the setup I have on my 9'er and I LOVE IT. It is harder to keep the front end on the pavement but if your thinking about doing something like this I doubt you'll really mind too much. I don't do too much highway riding but when I do its not unbearable.

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post #4 of 14 Old 06-26-2008, 01:37 PM
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ride to your local interstate
wind it up to about 70mph
down shift twice
ride around for two hours and get back to us

it's like losing a gear and a half w/ the approx rpm changes at any given speed up top

so that's the general impact up top, you lose that gearing and it's as if you're riding around in 4th and a half gear all the time (kind of annoying on the highway)

BUT

the upside comes on the low end, your first and second gear are changed quite noticeably. you can feel a brutal first gear that is mostly unusable unless you stay all over the front end. (meaning if you whack it to WOT, she's gonna stand right up)

2nd gear pulls nicely and goes by quickly
3rd gear and she starts to mellow out again with the regular electric motor like torque of the standard 9r setup

it's an easy inexpensive change that yields everything needed for the stoplight hero.

put it this way, swap out the gears and go for a ride w/ your regular riding buds, they'll be asking you, 'hey, whuddya do to your ride mang?'

having said all that, she runs right out of gas up top, you're gonna max out below 115mph so for a track setup, it'd have to be a real tight little course to make it worth it.

oh yeah, and it'll make the 9 fast enough to stay w/ a pinging, out of tune, 30yr old kawi turbo <g>

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post #5 of 14 Old 06-26-2008, 01:43 PM
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pretty much what rob said

and i'll say this, everyone who thinks about this should really check out a throttle plot from the pc3 if they have one or just pay attention...how much or how long do YOU actually have your throttle pinned 100&#37; WFO ?????

cause that's the deal down low, like rob said, if you can bury it, what's the point? if you can't manage a 16/44 or 15/43 in first, you're gonna lose the benefit in first and really only get max benefit out of 2nd/3rd

having said that, ride w/ the 15/45 for a spell and happen to be one of the larger sized riders and well, you can thrash the snot out of it

still, have after a few hours i start thinkin about changin the gearin to somethin a little less brutal...i never do, but i think about it

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post #6 of 14 Old 06-26-2008, 02:39 PM Thread Starter
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Thanks for the replies guys! It sounds like the 15/45 is going to be a little too much down low and not enough up top. What are your recommendations for the best overall 1/4 mile drag setup? Stock traps were around 114-115 in 4th gear.

'02 919
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post #7 of 14 Old 06-26-2008, 03:18 PM
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Hell I'm gonna do it but I'm also gonna get a 17 tooth job as well so I can really screw with it. Changing sprockets is really not that big a deal. I read somewhere that the 3:1 is where best performance is

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post #8 of 14 Old 06-26-2008, 03:30 PM
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Thanks from me, too, I do mostly highway and don't really want to compromise that.

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post #9 of 14 Old 06-26-2008, 04:03 PM
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I split the difference and went with 16/44 (2.75:1), after trying 17 (2.53:1)then 15 (2.86:1) with the stock rear sprocket.
As mentioned above, it's fairly cheap and really easy to swap out the gearing so you could buy a 44 and 45 rear and a 15 and 17 front and have fun trying all the different ratios out. Keep what you like and sell the rest. But it's quicker and cheaper just to do the quick math and find a ratio that will put you in the ballpark of where you want your power to be. I found 2.75:1 to be a very good overall ratio.
Sorry I can't help you with a drag-strip setup.

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post #10 of 14 Old 06-26-2008, 05:36 PM
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You guys rock, thanks for sharing.

.XLS spreadsheets only go so far in heling me understand functional changes something like this makes.

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post #11 of 14 Old 06-27-2008, 08:26 AM
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I run a 45 tooth rear and switch the front around between a 16 and 17 tooth. I drag race some and the 16/45 is really to short. It lifts the front end hitting 4th. I've mod'ed the bike some and it's total weight with fuel and my 210lbs is 605lbs. I run low 11s with the 16/45 but it's almost impossible to get the front end down. I'm going to the track July 2nd with the 17/45 and right now it feels quicker because it pulls longer in each gear. Time slips will tell. Changing to a 45 rear is nice and it gives a ton of options.

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post #12 of 14 Old 06-27-2008, 12:20 PM
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I have a 15/45 setup. It's a bit too aggressive for long-term highway usage, but I can keep up with my sport bike friends...

Michael Reyes

2002 Honda 919 / 2009 Honda Civic Si Sedan
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post #13 of 14 Old 03-28-2012, 06:45 PM
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Wow, Im a little behind but still this helped with all my questions. Im going to have to pass on the 15/45....I like the freeways most of all. Im going 16/44 or back to factory15/43.

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post #14 of 14 Old 03-28-2012, 07:09 PM
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Quote:
Originally Posted by danny.means View Post
Wow, Im a little behind but still this helped with all my questions. Im going to have to pass on the 15/45....I like the freeways most of all. Im going 16/44 or back to factory15/43.
factory is 16/43. if you like the freeways most of all, you'll LOVE the 17/44 combo, i promise you! give it a whirl, you wont regret it.

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