[nasirkaka]

Installing a 15T front sprocket on Triumph Scrambler 400x.

The gearing on the Scrambler 400x is short. First two gears feel like they don't even exist. Even at the top, one keeps searching for the 7th gear.

Speed 400 comes with a 15 teeth front sprocket. Scrambler 400X comes with 14 teeth. I am not too convinced with the idea of reducing one tooth on the 400X. Speed itself is sort of short-geared which makes the Scrambler super short-geared. It definitely adds to the peppiness but at the cost of snatchy and jerky nature in the first two gears. Even on the trails/offroad, the throttle modulation is a bit tricky and one may end up feathering clutch more than required. Or end up spinning the rear with some accidental extra throttle inputs causing trouble. These were not aligning with my riding requirements.

Digging a bit on the subject revealed that many riders (mostly abroad) have installed 15 teeth front sprocket on the 400X to increase the gearing and make the rideability calmer and relaxed. At the first service, I had requested to replace the front sprocket with Speed's, but the service center did not have it in stock. Chain/sprockets are basic consumables and not having them in stock for a bike which is been in the market for more than a year, is just not acceptable.

Some more digging revealed that the sprocket for the Duke 390 and Dominar 400 is 19T and fits the 400x. The locking mechanisms differ but essentially the basic sprockets are similar in design and can be used on each-other (all come from the same parent which is Bajaj). People had already tried them and it was easy to follow the route.

I've been trying to source one from KTM and they also sell the complete sprocket kit with the chain. Have not been successful with Bajaj as well.

Last Saturday I met another BHPian Redliner at Indiranagar, Bangalore. He rides a 390ADV and is well versed with the Bajaj / KTM service center which is on 17th Main. He has also experimented with various sprockets on his 390Adv and knows the service team there. With his PR skills and charm, we managed to get a 15T sprocket for KTM 390. May be you can try there next time to source one. They only cost Rs. 270.



Spent the better half of yesterday trying to swap the sprocket. Being Sunday, most garages would be closed. I had seen some videos of sprocket swap on YouTube and it appeared simple enough to self attempt. I had big size Hex sockets too (24mm for wheel and 27mm for sprocket nut). So thought to attempt this as DIY, only to later realise that it was not as simple as it appeared in the videos.



First step was to loosen the rear wheel nut and chain tension nuts generously and push the rear wheel forward so as to achieve good amount of slack on the chain.

It was easy to remove the plastic sprocket cover, which reveals a sheet metal secondary cover inside. This cover is also easy to remove but one struggles a bit to remove the plastic cable manager tags which are snap-slided in place. Removing the secondary sheet metal cover reveals the front sprocket. In about 6 weeks of ownership, there was lot of muck (dust and sand mixed with chain lube) accommodated around the front sprocket area. Cleaned it nicely and removed the sprocket bolt which required a bit of effort and strength.



Now this sprocket bolt was given very generous application of Blue thread lock at the time of factory assembly. The liquid had penetrated around the sprocket shaft jamming it all together. We can see some remains of the thread lock around the area.



There is also a special washer to prevent the sprocket nut from loosening. This is bent on one side to prevent accidental loosening of the nut. I had to pry it open with a screwdriver and remove the washer. No worried there, that's how its done. It would be ideal to replace that washed with a new one, but I had to re-use it as I did not have a spare. People in most of the videos I saw also had re-used the same.



Main trouble I had was to get the old sprocket out. As mentioned, it had jammed on the shaft serration due to seepage of thread lock. With great difficulty and lots of effort with make-shift tools like a crowbar, I managed to get the stock sprocket off the bike. After that it was easy to replace the sprocket with the new one, and tighten them all back in place.



Post installation of the new sprocket, took the bike out for a short spin of 25kms. I must add, this is one of the best mods out there on the 400X which Rs. 270 can buy. The bike is much calmer, and the first two gears are now actually useful. We can be in 2nd and potter around at 20kmph without straining the engine. Definitely the snappy acceleration is slightly compromised but it still pulls strong with some added throttle input. This is a modification which everyone must try who is looking for a more calmer, more relaxed rideability at low speeds as well at cruising at higher speeds. Even the 6th gear feels much more relaxed and longer. The overall vibrations also seem to have settled down. I did some offroading for couple of km, and feel this sprocket works better there too. Bike feels more in control while standing up on the pegs and riding. Earlier I was shifting frequently between 1st, 2nd and 3rd. Now I was able to ride the same stretch in mostly 2nd gear.

Technically this sprocket change is suppose to make a difference of 7% in each gear, but its much more prominent in real life. Barring those riders who really enjoy to keep the revs boiling and ride hard and fast, and love that quick snappy acceleration, this mod works well for the rest. I certainly feel like I will be sticking with this setup. Lets see how I feel in longer run. Its not an expensive modification and easily reversible too, so worth a try for sure.

[Axe77]

Originally Posted by nasirkaka

Installing a 15T front sprocket on Triumph Scrambler 400x.

Thanks for this fantastic update Nasirkaka. Good to read your observations on this. This is one of the Mods I have had my eye on but want to ride with the stock a bit more before considering the change. The good thing I guess is that it doesn't cost much to toggle between each front sprocket and see what works better for each individual.

[aston_martyr]

Originally Posted by nasirkaka

Last saturday i met another BHPian Redliner at Indiranagar, Bangalore. He rides a 390ADV and is well versed with the Bajaj / KTM service center which is on 17th Main. He has also experimented with various sprockets on his 390Adv and knows the service team there. With his PR skills and charm, we managed to get a 15T sprocket for KTM 390. May be you can try there next time to source one. They only cost Rs. 270.

Brilliant mod, and it is one I am waiting to try out as well. With 8k on the ODO I know for sure that this would help while touring as well.
God knows that I have been trying to do this mod for several weeks now and with no luck in procuring the sprocket. I've tried 2 service centers of KTM and both of them denied selling the front sprocket alone, "It comes as a full set" is what they say. Will try to check and source from Bajaj now.

[Aditya]

Installing a 15T front sprocket on Triumph Scrambler 400 X - Posts moved to a new thread.

[Samarth 619]

Sprocket change has been one of the best & cheapest mod I ever did in my life too.

My Pulsar 180, which became 208 after the block piston upgrade saw many chain sprocket size changes over her life, when I was young and free for this kind of life.

My present bike, a 2013 Duke 390 is in a league of its own now. Its 152 kgs,44 bhp, BS3 machine, and now its undergeared by a huge margin using a chain sprocket kit from Duke 250.
I don't remember exact dimensions but the stock rear 44 has now become 46.
Front I don't remember, it was 15, now I'm not sure, maybe its 14 now.

But its a peppy city monster now. Can do an easy 60 kmph in 6th gear now. Can do 20 kmph in 3rd. As I only commute for now, I'm enjoying this change every day!

I don't think 0-100 must've improved as I touch 100 in 4th gear now, and gearshifts take time. But it is accelerating far better with-in gears.


I also wrote an article on sprockets, something by the name "World of Sprockets" on my first site Xbhp.
I can copy it entirely if Team-bhp can benefit from it, should I do that?

[Axe77]

Originally Posted by nasirkaka

Installing a 15T front sprocket on Triumph Scrambler 400x.

Hi Nasirkaka. I also shifted to the 15T but simply haven’t had the time to put highway miles on the bike with the change. Within the city, the bike is certainly not as snappy and it’s a lot more relaxed to potter around.

I had a question on the top end. No doubt it might feel a bit calmer and the acceleration also a bit muted but I wanted to know if you think what kind of difference did it make beyond 90 - 100 kmph. Does it cruise easier at early triple digit speeds now?

Thanks.

[nasirkaka]

Originally Posted by Axe77

Hi Nasirkaka. I had a question on the top end. No doubt it might feel a bit calmer and the acceleration also a bit muted but I wanted to know if you think what kind of difference did it make beyond 90 - 100 kmph. Does it cruise easier at early triple digit speeds now?
Thanks.

Hello!
I havent done much of highway ride with the 15T sprocket. Whatever little highway sections I have done over the last two weekends (in search of trails) has been mostly riding at around 90-100 kmph and not beyond. Also, I changed the front sprocket to 15T just after the first service, therefore do not have a clear point of reference as to how the bike felt at higher speeds with 14T sprocket.

Technically it should help I guess and even improve the top speed. I do remember watching some videos of the conversion and riders had positive things to say about high speed ride character with the 15T sprocket.

Yesterday, we did trails around Bettamugilalam which had some sections comprising of uphill climbs with loose gravel. I did notice that I was shifting to first gear frequently where as with 14T sprocket, I may have been in 2nd gear for those sections. No complains as such, just a matter of getting used to. Overall very happy with the 15T sprocket for my riding requirements. But for someone who like their rides to be aggressive, 14T may suit better.

[AulusGabinius]

Hi, so out of sheer curiosity I checked Gearing Commander and the stock setup for the Scrambler is 14 teeth front and 46 teeth rear. The datasheet looks like this for the stock and the combos are there as well:



Seems like going up one tooth at the front and down one or two at the rear sprocket would work out to a nice balance between both characteristics.

[boniver]

Upgraded to a 15T front sprocket on my KTM ADV250 after riding 20k kms on the stock setup (14T front), and I only wish I'd made this change earlier. The bike feels much smoother at highway speeds since the RPM at each speed has decreased now (resulting in a ~5kmph higher top speed in every gear as well).

Since my main gripe with the stock bike was the vibrations post 110kmph in 6th gear, this is a welcome change for me. The only downside is I now have to rev more to get going if I come to a stop on an uphill slope, but the trade-off is well worth it for me. I do need to shift gears more frequently in city limits now, but I don't ride much in peak traffic and hence it doesn't affect me much.

Good upgrade for someone who doesn't care much about acceleration and wants better cruising ability at high speeds. My bike is currently at 22,700 kms.

[nr07]

Hi,

Is there a similar mod I can do for the Speed 400? I was reading that it already comes with 15T rear sprocket.

I am not well-versed in these technicals. Would really appreciate some guidance.

[AulusGabinius]

Originally Posted by nr07

Hi,

Is there a similar mod I can do for the Speed 400? I was reading that it already comes with 15T rear sprocket.

I am not well-versed in these technicals. Would really appreciate some guidance.

Check out Gearing Commander for some guidance. As in the above post, I would suggest a rear sprocket with one or two less teeth. The gearing details from that website is below:



As you see, a rear sprocket with 2 teeth down should give it longer legs but retain some of the snappy acceleration.

[Renaissance Man]

Originally Posted by Axe77

I had a question on the top end. No doubt it might feel a bit calmer and the acceleration also a bit muted but I wanted to know if you think what kind of difference did it make beyond 90 - 100 kmph. Does it cruise easier at early triple digit speeds now?
Thanks.

Let us know if you see a difference on the top ahead. I don’t like the gruffness that is there at 100-110 and would be interested in knowing if the 15T helps.