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KTM Duke 390: Overhauling brakes & replacing the rear wheel bearing

23rd January 2024, 17:00 by Brij Gawde

Both KTM and Bajaj service centers did not have the new part so had to clean and reuse the old seal.

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Next up the rear brakes. I went to a Bajaj dealer and I got a seal kit for a pulsar. Pretty much all Bajaj and dukes use the same rear caliper so it should work, hopefully. I popped into the KTM dealership and got a couple of new front caliper bolts since the old ones looked tired. Once I was back home, I remembered I should have gotten a new battery belt as the one on the bike now was close to breaking. Oh well, there is always a next time.

This is how the old stuff looked

First step was taking off the wheel. I had never taken off a rear wheel before - I struggled a LOT with it. I just knew for some reason I'd suck at this and I did not disappoint myself heh. Hopefully, I don't ever have to remove the rear wheel again!

Took off the old rotor and ABS ring. This is 9 years of muck hidden behind the rotor.

After a few rounds of cleaning.

Things weren't so clean on the other side as well. There was a TON of rubber powder? as well as melted rubber.

Gave it a round of cleaning too and came up well

Insides of the swingarm were given a deep clean, and all old traces of chain lube and dirt were removed.

With the wheels done, I focussed back on the caliper. I made sure I removed the pads and extended the piston as much as possible by pumping on the pedal as much as possible. I pulled out the caliper and found the insides pretty clean with only a few black flakes.

The new caliper seal I bought was loose. Sigh. The smaller square seal was fine but the main square seal was very loose.

The old seals weren't leaking anyway so kept them as is. The piston had some kind of damage? It had a significant lip that stopped the piston from going back in. Filed off the excess and I could put it back in the caliper.

Rear caliper is ready for reassembly. The caliper now moves far far smoother with the proper lubricant for the pins. Replaced the bleed screw with a new unit since the old one was almost rounded.

New parts going in - Rotor, pads, ABS rings, bolts for ABS rings, rotor bolts, and new cush rubbers. I painted the rotor with the same color as the silver I've used on footrests.

New parts were all assembled and it was time to put the wheel back in. While struggling with the spacer that goes on the sprocket hub, I noticed what looked like two balls just hanging out just inside the oil seal? So I took out the oil seal and was greeted with this.

Few days back, I adjusted the chain and tightened it. While riding it, I heard a loud BANG when moving around 20KMPH. I slowed and stopped, but couldn't find anything wrong and carried on. A day alter, I asked my mech why does my chain whine a LOT after tightening it? He told me I had over-tightened the chain and now it's making a racket. oh well, I thought I could fix it during the rear overhaul but oh boy was I wrong...

Next day, I tool the sprocket hub to my mechanic. He used his tools to take out the old bearing race that was stuck inside. It was time to put in a new bearing - A 6005RS. But wait, it's too small.What's going on?

The Indian parts catalog clearly says it's a 6005RS (highlighted in yellow) but it doesn't fit. Turns out I needed a 6205. Even the nuts holding the sprocket are mentioned as M10x1.25 (highlighted in pink) but in reality, they are M8 nuts. So I bought a pack of 6 M8 ss nyloc nuts to replace the plain black ones.

The EU/USA parts catalog had the right dimensions and parts. It's rare to see a mistake at this level though.

The old oil/dust seal for the sprocket bearing was CAKED with metal shavings and parts of the bearing cage. Both KTM and Bajaj service centers did not have the new part so had to clean and reuse the old seal. The inner lip is damaged in a couple of spots. I have placed an order for a new seal and will replace it whenever it arrives.

Rear is finally done and assembled back. Bleeding the rear caliper as always was a B***H but it was done.

With the rears done, I wanted to finish off the front as well. Propped up the front using two more jack stands on the leg guards and took off the wheel.

New parts for the front including EBC HH brake pads. This time I went with matte black for the front rotor like the new Dukes.

Everything is put back together. Phew.

The excessive paint wore off almost immediately. This left nice clean lines where the pads don't make contact and will prevent that part of the unused rotor from rusting in the future. The rear brakes are now more effective than before BUT they still suck. At this point, I have overhauled everything in the rear brake circuit except for the ABS pump. Oh well, the front feels much better thanks to the new rotor and EBC HH pads.

There are more electrical gremlins. The horn stopped working after one honk, I suspect some water got into the fuse box, caused a short, and blew the fuse. Turning on the key sometimes does not turn on the Speedo console and I have to turn it off and then on, it works. Pressing the start button there is half a crank, everything goes silent for half a second, the crank resumes, and the bike starts. I'm guessing it's the bad battery that's causing these problems. I'll be out of towen this weekend and will give the battery for replacement during that time. It takes a few days for it to complete so I should get the new battery once I'm back.

Oh, the rear seat lock refused to work at the KTM service center when I went to buy a new battery belt. Putting the seat back and pressing did nothing. Rode back slowly to my mechanic, he had a look and said the locking portion isn't retracting to lock the seat and needed replacing. Oh great more parts to replace. Sigh. I later tried again and the seat locked!! Opened it up, tried again to be sure and it worked again lol. I'll open the bottom panel and probably grease the lock again. If the problem recurs, I'll replace it.

I had to go to Bangalore for a few days for work and decided to use the bike instead of the train. Managed to put about 400KMs and had a great time on the highway.

While I was at the town I went to Khivraj and got the Sprocket/Coupling dust seal! Also got a set of Husqvarna indicators and Brembo sintered brake pads as spares.