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XR600R 15/42 or 15/40

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Ok so I recently just upgraded from 14/45 to 15/45 and the highway riding improved as is less buzzing. However I'd like to cruise at highway speed (65-70mph) as comfortable as possible. And achieve good mpg. My riding is about 90/10.

 

I've read a lot about this topic but it mostly seems to come from 650 users and not 600r. I feel that 15/42 will certainly get me there, but is 15/40 better? How much better? (Not mathematically, but in your opinion) Will it end up being too damn tall that at a stop light she'll want to just fly right away? Lastly, can it be harmful to the tranny to run this, seems like it will be working harder in the first 4 gears..

 

Thanks.

 

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Not sure if you would even notice the two teeth difference.  Might want to try 3-5.  Depending on your pockets you can buy a variety of sprockets and dial it in to your own liking.  Good luck,  you will be happy when your done.

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Youd most definitely notice two teeth difference.

Im all street on one xr6r. Street tires, street suspension, cush hub. Built it first with a stock motor with 15/43... then rebuilt motor with the nx fifth. And went to 15/45. Best yet and 100 is very likely. But I stayed around 85 very comfortably.

Get an nx fifth from www.motobike.jp, a gasket set, and a new set of rings. Youd be done in a day if you have all the tools

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Not sure if you would even notice the two teeth difference.  Might want to try 3-5.  Depending on your pockets you can buy a variety of sprockets and dial it in to your own liking.  Good luck,  you will be happy when your done.


Yeah I kind of figured in the long run I'd end up with a box full of various sprockets.

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Youd most definitely notice two teeth difference.
Im all street on one xr6r. Street tires, street suspension, cush hub. Built it first with a stock motor with 15/43... then rebuilt motor with the nx fifth. And went to 15/45. Best yet and 100 is very likely. But I stayed around 85 very comfortably.
Get an nx fifth from www.motobike.jp, a gasket set, and a new set of rings. Youd be done in a day if you have all the tools


Ok, never heard of that but will have to look it up. Thanks.

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You won't hurt your tranny as long as you don't lug it, just might wear your clutch a little more on take off but that is minimal.

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I use 15/40 and love it. I can cruise comfortably at 60-70 but would go to 38 if I was trying to ride on the freeway all the time. Better to mod fifth gear or I remember someone mentioning about changing first and maybe second so it was better with the very tall final drive ratio.  Joerc51? I like the closer ratio of the xr600r transmission. You could also change the ratio from the crank to the clutch with 650L parts. I was thinking about doing that. 

Edited by ricky racer
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Its the best thing to do to this bike, besides giving it MORE power


After a bit of research, wow, yes this seems like the very best option, and still be able to do trails too..

Quick question though, is this the part number I'd be looking for..?
23491-MW2-780
Or am I way off here...

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I use 15/40 and love it. I can cruise comfortably at 60-70 but would go to 38 if I was trying to ride on the freeway all the time. Better to mod fifth gear or I remember someone mentioning about changing first and maybe second so it was better with the very tall final drive ratio.  Joerc51? I like the closer ratio of the xr600r transmission. You could also change the ratio from the crank to the clutch with 650L parts. I was thinking about doing that. 

 

Awesome, thanks. Yeah 40 sounds like a good option then for me because that's really all I'm looking for (for now). I am definitely considering the fifth gear mods for the future.

 

But how is 15/40 on the streets? How do the first few gears feel?

If it's manageable I'd go for this, but if not, then I might just wait to do the fifth mods.

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23491-MW2-780

motobike.jp

Hardest part of the switch is getting the clutch basket off! (Impact, not hard), get circlip pliers. And a gasket set.

If youre trying to have that low end pull, dont go smaller in the rear. My exact reason initially to put the nx fiftg in and go up from 43 to 45t in rear. Im sure 40 is ok. 38 is probably fine. Unless your driveway is a hill. Beauty with the rear, you can switch it easier than an in the case tranny gear.

Keep in mind you can always swap from 14 to 15 and have a nice torque change.

But I want to say that before my fifth mod,  I rode 15/43, changed oil regularly, I got thrust washers shavings. I did a weekly 100 mile (100up, 100 back so 200 miles additionally each week.) On freeway. Pushing 80. Tattered up my oil pump. Called for a full rebuild, so I put in the nx fifth. Haven't had thrust washer issues. Could be affiliated, could be coincidental.

If you go in and everything is 25 years old, get more new parts.

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8 hours ago, BoaConstrictor said:

 

Awesome, thanks. Yeah 40 sounds like a good option then for me because that's really all I'm looking for (for now). I am definitely considering the fifth gear mods for the future.

 

But how is 15/40 on the streets? How do the first few gears feel?

If it's manageable I'd go for this, but if not, then I might just wait to do the fifth mods.

I think its fine but my bike is heavily modified. Not much clutch slip at all to take off. I can also blow right through that gearing almost as fast as I can shift. First is a little tall and the rest are still close feeling to me. It will now go way faster than I need to go on a dirt bike! Bike accelerates faster than it will stop hahaha.

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6 hours ago, notoriousE-R-I-C said:

23491-MW2-780

motobike.jp

Hardest part of the switch is getting the clutch basket off! (Impact, not hard), get circlip pliers. And a gasket set.

If youre trying to have that low end pull, dont go smaller in the rear. My exact reason initially to put the nx fiftg in and go up from 43 to 45t in rear. Im sure 40 is ok. 38 is probably fine. Unless your driveway is a hill. Beauty with the rear, you can switch it easier than an in the case tranny gear.

Keep in mind you can always swap from 14 to 15 and have a nice torque change.

But I want to say that before my fifth mod,  I rode 15/43, changed oil regularly, I got thrust washers shavings. I did a weekly 100 mile (100up, 100 back so 200 miles additionally each week.) On freeway. Pushing 80. Tattered up my oil pump. Called for a full rebuild, so I put in the nx fifth. Haven't had thrust washer issues. Could be affiliated, could be coincidental.

If you go in and everything is 25 years old, get more new parts.

Yeah most people spin to many RPM on the freeway leading to premature wear and oil temp problems.

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9 hours ago, BoaConstrictor said:

But how is 15/40 on the streets? How do the first few gears feel?

The only one that matters is first gear, all the rest are fairly uniform jumps from there.  Try starting out in second gear sometime, which will be higher than first gear will ever be even with the most extreme high gear sprocket combination.  An XR650 can make a pretty smooth start in second gear, so there shouldn't be anything to be concerned with.  As long as you don't feel like the engine is bogging down after you let the clutch out, you're fine.

One time as an experiment, I tried starting out on a flat surface in each of the five gears.  It was fairly easy in first, second and third, and I was able to do it in fourth and fifth too, although I wouldn't expect my clutch to last very long if I kept doing that.

Personally, I feel that 15/45 is optimal for street use on an XR650L, but I'm sure my bike would work just fine if I had 15/40 gearing.  I wouldn't want to ride it off road with that gearing, though, and usually prefer to go at least 14/45 in the dirt.

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3 hours ago, ScottRNelson said:

The only one that matters is first gear, all the rest are fairly uniform jumps from there.  Try starting out in second gear sometime, which will be higher than first gear will ever be even with the most extreme high gear sprocket combination.  An XR650 can make a pretty smooth start in second gear, so there shouldn't be anything to be concerned with.  As long as you don't feel like the engine is bogging down after you let the clutch out, you're fine.

One time as an experiment, I tried starting out on a flat surface in each of the five gears.  It was fairly easy in first, second and third, and I was able to do it in fourth and fifth too, although I wouldn't expect my clutch to last very long if I kept doing that.

Personally, I feel that 15/45 is optimal for street use on an XR650L, but I'm sure my bike would work just fine if I had 15/40 gearing.  I wouldn't want to ride it off road with that gearing, though, and usually prefer to go at least 14/45 in the dirt.

The op has a xr600r which is why he needs higher gearing than you. 15/45 on his bike would be to high RPM's while trying to cruise at 70. 50-55 is ok at 15/45.  IMO 

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23491-MW2-780
motobike.jp
Keep in mind you can always swap from 14 to 15 and have a nice torque change.


Definitely one of the reasons now I want to do the fifth mod now.



Tattered up my oil pump. Called for a full rebuild, so I put in the nx fifth. Haven't had thrust washer issues. Could be affiliated, could be coincidental.


Hmmmm.. how long did you drive at 15/45? Did it never seem to pose issues?




If you go in and everything is 25 years old, get more new parts.


It's a 97 so almost there..

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Yeah most people spin to many RPM on the freeway leading to premature wear and oil temp problems.



Yeah this is exactly what I'm worried about.

Makes me want to install a tachometer.

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Try starting out in second gear sometime, which will be higher than first gear will ever be even with the most extreme high gear sprocket combination. 


I've actually done this on accident quite a few times and honestly it felt like first to me, I could hardly tell until I caught a little speed.



An XR650 can make a pretty smooth start in second gear, so there shouldn't be anything to be concerned with.  As long as you don't feel like the engine is bogging down after you let the clutch out, you're fine.


I see. Ok. But I have an xr600r..



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The op has a xr600r which is why he needs higher gearing than you. 15/45 on his bike would be to high RPM's while trying to cruise at 70. 50-55 is ok at 15/45.  IMO 



I totally agree. 50-55 is best, 60 is 'ok', 62-65 is .... meh... manageable..

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