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Gearing - 13/43 vs. 13/40

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When I bought my used 2016 LRP back in March it came with 13/43 gearing.  While I like the low-end grunt of the first three gears I often find myself hunting for 7th gear when I'm on faster paved roads.  While I don't ride on the highway very often and don't need to go 70+ mph for long stretches, it would be nice to be able to cruise comfortably at 60-65 mph for an hour when I need to without the engine screaming.

Since I already have the 43 on the back, going down to a 42-tooth seems almost pointless, as I doubt I'd be able to tell the difference.  Or am I wrong about that? 

My question is how much low-end grunt would I sacrifice by going down to a 40-tooth on the rear?  I ride a mix of light off-road, gravel/dirt roads with some paved county roads and hardly any highway.  But I regularly get up to about 60-65 mph when on pavement.  I'm struggling to choose between a 40-tooth and a 42-tooth.  I intend to keep the 13-tooth up front.  I'm looking for that perfect combo, and I don't want to give up too much low-end torque while gaining some higher speed cruising capability.

Edited by Ocaptainmycaptain

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I did 13 40. I switched back to 14 40. Cut too of airbox off and drilled 8 holes in the baffle. Helped slightly. I prefer 14 40 for milage purposes

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A cheap way to achieve almost 13/40 is to go 14/43. Both these combos are 3.07 and are for all intents and purposes, identical ratio's. To work this out, divide the big number by the small number ie 43 divided by 14.

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30 minutes ago, huckinnz said:

A cheap way to achieve almost 13/40 is to go 14/43. Both these combos are 3.07 and are for all intents and purposes, identical ratio's. To work this out, divide the big number by the small number ie 43 divided by 14.

I thought about doing this, except I don't have enough slack in my chain (which I just bought and installed) to accommodate a 14-tooth sprocket, so I'm committed to the 13 for now.  When my current chain wears out I'll likely change to 14/43 or 14/42 at that point.

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I originally ran 14/42 on my bike. I recently switched to 13/42 really like the low end power and still have enough for the road at higher speeds.

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On 9/30/2019 at 5:34 PM, Ocaptainmycaptain said:

it would be nice to be able to cruise comfortably

It really is amazing what a difference good quality foot pegs can do in this regard not to mention bars and grips. I am currently running 13/44's and often have the same thoughts as you. I think I would like to run 14/44's  just to see ...    

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23 hours ago, gnath9 said:

It really is amazing what a difference good quality foot pegs can do in this regard not to mention bars and grips. I am currently running 13/44's and often have the same thoughts as you. I think I would like to run 14/44's  just to see ...    

I ended up installing a 40-tooth Supersprox on the rear that I got on Ebay.  Took her out for a quick 25-mile spin last night, and I love it.  It's perfect for me.  First gear is still low enough to be very useful off-road, but now I'm not rowing through all six gears very quickly.  5th and 6th still pull strong enough, and the engine isn't screaming at 55 mph.  It actually makes the volume of the FMF exhaust more tolerable, since I've been recently contemplating going back to stock exhaust.

I agree with you on good quality pegs.  My normal go-to pegs on all my bikes have been the Moose Racing pegs. They're great pegs. But after putting a set on my CRFL I found out that I won a set of IMS pegs from some organized moto event I rode last year.  The IMS rep let me choose any of their pegs that I wanted, so I opted for the monster Rally pegs, and these things rock!  So much room, and very comfortable for standing.  See comparison pics below. Top peg is the Moose Racing peg and the Rally right below it.  Piece of white bread for comparison. ?

CRF250L-40-tooth.jpg

CRF-IMS Rally-left peg.jpg

CRF-Top view of IMS Rally pegs.jpg

Edited by Ocaptainmycaptain

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When I installed the 40-tooth Supersprox I mangled the existing sprocket bolts a bit.  I assume they're the stock bolts (I'm not the original owner), but man are those hex holes soft and easy to strip.  I realized afterwards that the hex holes are really just to hold the bolt in place while all the force should be applied to the sprocket nuts.  Oh well, I've learned my lesson.

Can I use these sprocket nuts/bolts on the new sprocket?  I like that they're black and match the new sprocket.

https://www.rockymountainatvmc.com/parts/bolt-hub-savers-double-locked-sprocket-fastening-kit-p?c=13

Or do I have to specifically use Supersprox bolts such as these:

https://www.rockymountainatvmc.com/parts/supersprox-sprocket-bolt-and-nut-kit-p?v=12948

Pic of the new sprocket:

CRF-IMS pegs.jpg

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On ‎10‎/‎5‎/‎2019 at 8:51 AM, Ocaptainmycaptain said:

Piece of white bread for comparison.

🤣

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I tried both 13/42 and 13/40 when i put on new sprockets and a new chain last.

My very subjective reflection was that the 42 tooth made first gear into a "crawl" gear, and the 40 tooth made sixth into an "overdrive".

The 42 makes you rev the engine higher (i FEEL like its a little to high) at highway speeds, but not miserable. The lower first gear is an advantage in super technical stuff, like going over a log or such. On trails and most terrain i find myself going to second almost immediatley after taking off though. Of course this might just be a habit from years with the 40 tooth.

The 40 tooth leaves the sixth gear just high enough for high speed cruising. If i really want to wring the last power out of the engine, i typically accelerate to 105 km/h in fifth, and go to sixth to keep the revs down. It can be done in sixth too, but fifth gets there faster. First gear is low enough for technical terrain, and i have never felt that the lower first of the 42 tooth would have made a real difference.

I ride my 250 trough anything. Mud, trails, straight into the woods, illegal motocross areas, highways, long distance trips, and i also use it around the farm. The 14/40 is the best compromise for me. Its the lowest one can go without sacrificing highway performance.

If i were to use it strictly offroad i might look into lower gearing, but then i probably would do 13/45 or something. Good clutch technique is a valid replacement for lower gearing on a dual sport.

I have no efi controllers, and an open slipon exhaust.

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Hey I been thinking of going with a slipon. What did you go with?

I tried both 13/42 and 13/40 when i put on new sprockets and a new chain last.
My very subjective reflection was that the 42 tooth made first gear into a "crawl" gear, and the 40 tooth made sixth into an "overdrive".
The 42 makes you rev the engine higher (i FEEL like its a little to high) at highway speeds, but not miserable. The lower first gear is an advantage in super technical stuff, like going over a log or such. On trails and most terrain i find myself going to second almost immediatley after taking off though. Of course this might just be a habit from years with the 40 tooth.
The 40 tooth leaves the sixth gear just high enough for high speed cruising. If i really want to wring the last power out of the engine, i typically accelerate to 105 km/h in fifth, and go to sixth to keep the revs down. It can be done in sixth too, but fifth gets there faster. First gear is low enough for technical terrain, and i have never felt that the lower first of the 42 tooth would have made a real difference.
I ride my 250 trough anything. Mud, trails, straight into the woods, illegal motocross areas, highways, long distance trips, and i also use it around the farm. The 14/40 is the best compromise for me. Its the lowest one can go without sacrificing highway performance.
If i were to use it strictly offroad i might look into lower gearing, but then i probably would do 13/45 or something. Good clutch technique is a valid replacement for lower gearing on a dual sport.
I have no efi controllers, and an open slipon exhaust.

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I think its just some universal one named "Dominator". Took this picture just for you haha

If you are going to invest money, i think you should get the whole system. The bend closest to the cylinder is two walled and kind of thin on the inside, eg restrictive.

2019-10-10 16.52.52.jpg

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I think its just some universal one named "Dominator". Took this picture just for you haha
If you are going to invest money, i think you should get the whole system. The bend closest to the cylinder is two walled and kind of thin on the inside, eg restrictive.
5270873_2019-10-1016_52_52.jpg.f3347f765a5cc629c313f889fab7ec1f.jpg
I was thinking about a whole system but don't want to get a piggyback efi controller. I guess I'll use a wide band afr to see if I need to or not if and when I get a system. This thing doesn't run as lean as people think. Definitely not as lean as a stock 450l. I wish there was a way to read my current o2 sensor. Is it possible?

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