DIY: Installed KTM's 15T Sprocket on my Triumph Scrambler 400 X

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.

BHPian nasirkaka recently shared this with other enthusiasts.

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

The gearing on the Scrambler 400x is short. First two gears feel like they dont 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 endup feathering clutch more than required. Or endup 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 ridebility calmer and relaxed. At the first servie, i had requrested 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 apprearted 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. Rmoving 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) accomodated 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 threadlock 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 threadlock 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, thats 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 tigethen 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 ridability 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 kms, 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.

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