Gearing Up (or down) 401
- Thread starter BISavage
- Start date
OP
BISavage
champion rider
That looks better than I thought it would.
Vintage Veloce
pro rider
The center section is 4mm thick and the edge 6mm.
What are you using for sprocket nuts?
Vintage Veloce
pro rider
Picture of the back. The big circles seem to have been stamped from this side. The bolt holes seem machined.
OP
BISavage
champion rider
I cleaned the original ones and continue to use them.
They match the rest of the screws.
Have consider prettier ones.
Not the top of my list though as my chain comes off like every other month.
OP
BISavage
champion rider
Vintage Veloce
pro rider
Wow, that looks different. I guess that is a Husqvarna / KTM specific bolt!
Vintage Veloce
pro rider
I noticed that the stock sprocket and the new Driven on have the appearance of the bolt holes being a bit uncentered between the lightening holes. The KTM Adventure stock sprocket earlier in this thread is also like this.
Stock 401:
Driven:
I called Driven about this out of curiosity, and they admitted it was so. The lightening holes are punched and They aren't they aren't as well located as one might hope. They said the bolt holes and sprocket concentricity (is that a real word?) should be good. That is hard to meaure, but will be easy to check when it is on the wheel and spun. ;-)
They also said the Aluminum sprockets are more accurately made, something about the steel ones being cheaper. I'm betting that maybe the aluminum ones are all machined instead of punched.
Stock 401:
Driven:
I called Driven about this out of curiosity, and they admitted it was so. The lightening holes are punched and They aren't they aren't as well located as one might hope. They said the bolt holes and sprocket concentricity (is that a real word?) should be good. That is hard to meaure, but will be easy to check when it is on the wheel and spun. ;-)
They also said the Aluminum sprockets are more accurately made, something about the steel ones being cheaper. I'm betting that maybe the aluminum ones are all machined instead of punched.
OP
BISavage
champion rider
Perfectly normal.
Worst issue I had was on a dual material sprocket where the aluminum was cut too little in the center hole and it required rework to fit on the sprocket holder.
Worst issue I had was on a dual material sprocket where the aluminum was cut too little in the center hole and it required rework to fit on the sprocket holder.
Vintage Veloce
pro rider
Anyone have the torque spec for the 2020 401 rear sprocket? It's M8-1.25.
I'm thinking about 35Nm?
I'm thinking about 35Nm?
OP
BISavage
champion rider
Same as the pre-20's normally, as the parts are the same; 25nm with Loctit 243
Vintage Veloce
pro rider
25Nm? That seems light? Are you sure?
I did some digging and the 390 Adventure shows 38Nm without loctite.
I have new nuts, so I am gong with loctite... but 25 seems low?
I did some digging and the 390 Adventure shows 38Nm without loctite.
I have new nuts, so I am gong with loctite... but 25 seems low?
Vintage Veloce
pro rider
You are correct, as usual!
The 2019 Svart 401 manual:
The 2020 KTM 390 Adventure manual:
The 2020 has flanged locknuts and no Loctite, so maybe that is the difference?
The 2019 Svart 401 manual:
The 2020 KTM 390 Adventure manual:
The 2020 has flanged locknuts and no Loctite, so maybe that is the difference?
Vintage Veloce
pro rider
Full installation report follows
Stock 2020 45T Sprocket: 1140g
Stock Sprocket Locking Flange Nuts (6): 48g
Driven Racing Steel 45T Sprocket: 745g
Titanium Sprocket Nuts (6): 26g (because they look pretty).
So the new sprocket and nuts save 417g or 0.92 pounds!
The sprocket nut torque is missing from the 2020 owners manual. And the Ti nuts say to torque to the normal manual specs.
The 2019 Svart 401 manual says 25 Nm with Loctite 243, but the 2020 KTM 390 Adventure Manual says much higher, 38 Nm without loctite. So I went with 27 Nm with loctite as that is an even 20 Lb-Ft on my torque wrench.
I marked them with a touch of red paint so I will notice any loosening.
As I have found with other bolts on this bike, a couple of the sprocket bolts had pretty rough threads and needed to be run through a die to clean up the threads.
It was the first time I removed the rear wheel on this bike. It was necessary to remove the chain guard, but then it was possible to maneuver the tire out past the brake caliper without removing that. (I disposed of the rear possum catcher long ago, so that wasn't an issue.)
It's a vanity sprocket, I just didn't like how the stock one looked and I wanted a lighter one. And of course it saves nearly a pound of unsprung weight!
Now the stock chain looks ugly...
Stock 2020 45T Sprocket: 1140g
Stock Sprocket Locking Flange Nuts (6): 48g
Driven Racing Steel 45T Sprocket: 745g
Titanium Sprocket Nuts (6): 26g (because they look pretty).
So the new sprocket and nuts save 417g or 0.92 pounds!
The sprocket nut torque is missing from the 2020 owners manual. And the Ti nuts say to torque to the normal manual specs.
The 2019 Svart 401 manual says 25 Nm with Loctite 243, but the 2020 KTM 390 Adventure Manual says much higher, 38 Nm without loctite. So I went with 27 Nm with loctite as that is an even 20 Lb-Ft on my torque wrench.
I marked them with a touch of red paint so I will notice any loosening.
As I have found with other bolts on this bike, a couple of the sprocket bolts had pretty rough threads and needed to be run through a die to clean up the threads.
It was the first time I removed the rear wheel on this bike. It was necessary to remove the chain guard, but then it was possible to maneuver the tire out past the brake caliper without removing that. (I disposed of the rear possum catcher long ago, so that wasn't an issue.)
It's a vanity sprocket, I just didn't like how the stock one looked and I wanted a lighter one. And of course it saves nearly a pound of unsprung weight!
Now the stock chain looks ugly...
Last edited:
OP
BISavage
champion rider
So, this is the next setup:
Esjot 15t - 196g (1g less than JT)
Esjot 45t - 308g (suprisingly weights 2g less than the 44 tooth, looks like the 44t has more similar cutouts to the 43t and the 45t has larger cutouts)
MXZ4 112 links
Esjot 15t - 196g (1g less than JT)
Esjot 45t - 308g (suprisingly weights 2g less than the 44 tooth, looks like the 44t has more similar cutouts to the 43t and the 45t has larger cutouts)
MXZ4 112 links
Vintage Veloce
pro rider
That looks great! Post pics when mounted please...
OP
BISavage
champion rider
Changed both tires and found it to be a good opportunity to upgrade all the grease to BelRay & hook up the drive kit; the other one needs a bath.
Didn't wanna bust out with fresh tires on a Friday night before their scrubbed though... and the rear shock will probably need about 2 turns softer with the shorter wheelbase.
does look good n Svart-ish now.
Didn't wanna bust out with fresh tires on a Friday night before their scrubbed though... and the rear shock will probably need about 2 turns softer with the shorter wheelbase.
does look good n Svart-ish now.
OP
BISavage
champion rider
Vintage Veloce
pro rider
White text in the tires!
But more importantly, nicely packed with mud.
But more importantly, nicely packed with mud.
Last edited:
OP
BISavage
champion rider
I went through a freshly plowed field just because I could 
Back on point, the Aluminum Sprocket is awesome!
It makes the chain seem quieter and smoother.
Cant comment on the handeling yet as im still fine tuning the preload.
Back on point, the Aluminum Sprocket is awesome!
It makes the chain seem quieter and smoother.
Cant comment on the handeling yet as im still fine tuning the preload.