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Discussion Starter #1
Over the winter I installed 15T front and 42T rear sprockets.

Front was KTM part 58033029115 - a dampened 15T sprocket.

For the rear I went cheap for the initial switch because I was not sure I'd like it. So a basic steel AFAM 42T sprocket for rear.

Reused the stock chain - no changes in chain length required as has been noted in other comments re this change. Also my bike only has ~2k km of mostly not-driving-in-anger on it so there is minimal chain wear/stretch. I'm not too worried about reusing the same chain on new sprockets.

Driving difference is immediately very noticeable. My butt-meter definitely measures a difference in low-mid grunt.

Personally I cannot see anything except positives re this setup. Well, maybe just that redline comes quite a bit quicker now in 2nd - just need to acclimatize to that.

RPMs at 100 kph are approx 4400 +/- a bit.

Highly recommended inexpensive mod for those mostly interested in enjoying lower end get up and go. I will stick with it and prob upgrade the 42T rear to a alum/steel lighter weight version sometime this year.

I also note that while traversing down my laneway at my usually leisurely ~30kph now that the RPMs are a bit higher the bike handles these slow speeds a lot smoother than before and I do not experience the annoying intermittent surging in the engine at those speeds as I was previously.

Anyway, just another subjective opinion on the 15/42 setup to add to the mix.
 

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Can I ask what is the OEM sprocket configuration front and rear, before you went to 15T/42T setup? Thanks.
 

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That's very interesting and a good report. I rarely use anything over 4th gear when going for it on our overcrowded roads so 6th is a motorway gear and I try to avoid those.

I'm troubled by the low speed surging so this might be a solution that cures that and gives me some more shove
 

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2020 790 Duke, 2006 SV 650, 2008 Hot rodded KLR, 1991 Honda Hawk NT 650
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For those trying this out I'd suggest doing only the front sprocket first. You might not require the effort and expense of replacing the rear one.
 
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2020 790 Duke, 2006 SV 650, 2008 Hot rodded KLR, 1991 Honda Hawk NT 650
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2020 KTM 790 Duke
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Discussion Starter #8
For those trying this out I'd suggest doing only the front sprocket first. You might not require the effort and expense of replacing the rear one.
Def agree with this approach. This is why I cheaped out on the 42T rear sprocket for now - I was not sure if I was going to like/keep the setup. But in my case, after trying the complete swap to 15/42 first, maybe 20min into my first ride out I pretty much decided "this is it" for me.

But as @Eon790duke said, you could certainly try swapping out just 1 to start and play with that - pretty sure some people on the forum have done just one.
 

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You can always play around on gearing commander to see what the changes will make for speed in gears. As for the 15/42 gearing, it would make a wheelie-prone bike even worse.

 

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I see the genuine damped 15t sprocket is 3 times the price of an aftermarket one. Do you feel a benefit to having a damped one or is a plain steel one as good?
 

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Discussion Starter #11
I see the genuine damped 15t sprocket is 3 times the price of an aftermarket one. Do you feel a benefit to having a damped one or is a plain steel one as good?
Whether it make a significant diff or not I cannot say, sorry.. but I note that the stock 16T sprocket is damped so I just decided to replace it with the same sprocket type.

I'm not sure about your local pricing, but to me:
1 58033029115 CDN$36.32 ENGINE SPROCKET 15 T DAMPED - ENGINE SPROCKET 15 T DAMPED
did not seem overly expensive so I went with it without exploring other options.
 

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Aftermarket one is £11 and the genuine KTM one is £34. If the non OE one creates more noise or vibration there's no difference I'll save the money and that'll pay for the rear one!
 

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I see the genuine damped 15t sprocket is 3 times the price of an aftermarket one. Do you feel a benefit to having a damped one or is a plain steel one as good?
Damped ones are supposed to be quieter. Could not see the point in cheaping out tbh. IIRC was about 15€ difference here. There is I think a US company that offers damped wheel sprockets too.
 

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Discussion Starter #14
Aftermarket one is £11 and the genuine KTM one is £34. If the non OE one creates more noise or vibration there's no difference I'll save the money and that'll pay for the rear one!
£34 is surprising. Here in Canada the KTM damped is only about £20. But still, considering the bike you're buying for, is even £23 really worth cheaping out on? 🤷‍♂️
 

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No, if the damped one offers a benefit. If there's no discernable difference there seems little point
 

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What price are REAR sprockets there? Here seem to be in the 30 Euro range and about 20% more for the KTM OEM.
 

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Discussion Starter #17
What price are REAR sprockets there? Here seem to be in the 30 Euro range and about 20% more for the KTM OEM.
I paid CDN$60 (~40 Euros) for an AFAM 42T steel sprocket.
KTM 75010051042 (42T stealth) is CDN$80
The KTM orange-alum/steel hybrid (OEM Supersprox I think) is CDN$100 (I think this is KTM 5841005104204 but I may be wrong on that).
 

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The KTM orange-alum/steel hybrid (OEM Supersprox I think) is CDN$100 (I think this is KTM 5841005104204 but I may be wrong on that).
Over here the Supersprox Stealh (hybrids) are 70 Euros - including made to measure (different tooth count)
The Supersprox all Steel is 27Euros. This is what the 42 tooth steel looks like
 

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That's very interesting and a good report. I rarely use anything over 4th gear when going for it on our overcrowded roads so 6th is a motorway gear and I try to avoid those.

I'm troubled by the low speed surging so this might be a solution that cures that and gives me some more shove
for those that are forced to endure city riding
before you get to the ride I’ve found by switching to rain mode the bike lives city traffic. It smooths things out nicely. After I hit the twisties I switch back to street or spirt
Mode.
 

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Aftermarket one is £11 and the genuine KTM one is £34. If the non OE one creates more noise or vibration there's no difference I'll save the money and that'll pay for the rear one!
You will pay allright! 😂
 
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