Well I have read some about the 17-tooth front sprocket swap for the 919. I know it lowers the RPMs at all speeds just a little bit, which is especially helpful for lowering the vibrations at highway speeds.

Have any of you 919 owners made this modification?

I have a few questions about it:

Does it affect the speedometer at all? (I figure it would if the speedometer pickup is on the front sprocket)
Are there any side effects to the precision with which fuel is delivered to the engine? (I am all about OEM, and I don't want to disrupt anything)
What sort of RPM drop can I expect in 6th gear?
Besides a minor loss in acceleration, are there any drawbacks to this modification?

Does it affect the speedometer at all? (I figure it would if the speedometer pickup is on the front sprocket)
Any gear changes affect the speedo. :wink:

The 919 speedometer is off anyway, mine seems to be a little more off than normal. Indicated 80mph is really about 73 on my gps...Changing the front to a 17 is supposed to bring the speedometer closer to being accurate. Since our bikes don't read off the front wheel, changing the gears will change the speedometer. Also, having the biggest sproket will make it easier on your chain. Here the thread where I was talking about doing the same...

http://www.honda599.com/forums/showthread.php?t=7634

There's some good info in there

Makes sense, I like that calculator tool for gearing changes.

Let me know if you change yours, I would be curious to hear your firsthand experience.

Any gear changes affect the speedo. :wink:

The speedometer accuracy would not be changed by a different sprocket if the speed was picked up from the front wheel.

The speedometer accuracy would not be changed by a different sprocket if the speed was picked up from the front wheel.
Right. But it's not. ;)

It's as much as 10% too optimistic in stock form. Typically 5-7%. Gearing it up will make it more "true", while gearing it down will make the discrepancy worse.

I used the little formula have my bike as close as it could be at 70. Mine reads 70mph at 4000rpm. So, I'll probably go to a 17/41 instead of the stock 16/43. but it's been brought to my attention that is pretty extreme. But I want the lower rpm's for the longer distance riding I like to do.

Yeah I want to shift mine for long distance riding too, but I realize that this will shed some of the fun-factor of running through the gears. I like a small change like the 17t front, but I don't know that I would want to go much more than that.

It's nice that sprockets aren't too expensive, and it can be easily undone!