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Discussion Starter · #1 ·
Hi. The rear suspension of my 2017 Duke 390 seems to bottom out. When I reached out to the service center they say that the suspension needs to be changed. I have done only 9000km. I had changed my rear tyre at 5500km. Now my doubt is whether I can recondition the monoshock from a nearby mechanic? Is it advisable? It costs only 30% of the new suspension. Please suggest as I do not have much idea on this.
 

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Discussion Starter · #3 ·
How much do you weigh? Have you tried setting the preset to max?
I weigh 85 kg. I tried to adjust the preload by 3 steps. But the suspension feels so hard at that point and there doesn't seem to be much action from the suspension. Basically it feels like all the spring action is gone.
 

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If you have ridden this bike for 9,000km you must know if this is a recent occurrence or if it has been like this all the time.
Can you see if there is an oil leak?
Refurbishing the shock is very doable and if your mechanic knows what he/she is doing it should be as good as new.
 

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Discussion Starter · #5 ·
If you have ridden this bike for 9,000km you must know if this is a recent occurrence or if it has been like this all the time.
Can you see if there is an oil leak?
Refurbishing the shock is very doable and if your mechanic knows what he/she is doing it should be as good as new.
Hi. There is no oil leak and this has been a gradual degradation.
I started to feel the tail tidy hitting the rear tyre hugger around 6 months back. It started to become gradually more and more to the point where when I have a pillion it is sure to touch on a small pothole.
When I asked the service center about this (my warranty periods was alive at this point), they said the problem is with the tail tidy and not the suspension. Now after the warranty is over they say that it needs to be changed!
 

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Obviously, this has nothing to do with altering the mudguard.
It could be that the oil valve plates inside the shock are not functioning as need be and let through too much oil during compression.
I would definitely have the shock checked and rebuild, perhaps even fill it off with a 1 point heavier oil.


Hi. There is no oil leak and this has been a gradual degradation.
I started to feel the tail tidy hitting the rear tyre hugger around 6 months back. It started to become gradually more and more to the point where when I have a pillion it is sure to touch on a small pothole.
When I asked the service center about this (my warranty periods was alive at this point), they said the problem is with the tail tidy and not the suspension. Now after the warranty is over they say that it needs to be changed!
 

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Discussion Starter · #7 ·
Obviously, this has nothing to do with altering the mudguard.
It could be that the oil valve plates inside the shock are not functioning as need be and let through too much oil during compression.
I would definitely have the shock checked and rebuild, perhaps even fill it off with a 1 point heavier oil.
Sure. Thank you so much. May be now I ask my mechanic to do a rebuild for me.
 

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Don't rebuild a faulty shock absorber. Unless you have a shock absorber oil leak or excessive bottoming even after adjusting the suspension, there's not point rebuilding, once replacing is the option. Try stiffening your suspension and see if it helps.

Good luck.

Cheers!
VJ
 

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What a very strange reply/advice?
On what do you base this?
What do you mean by 'stiffening' if the OP clearly stated the deterioration of the shock was gradually over the past 6 months and he cracked up the preload by 3 klicks without the desired effect?
If, like you perhaps, you have the cash to through around I would advise fitting an Öhlins, K-Teck or Bitubo fully adjustable shock.

Don't rebuild a faulty shock absorber. Unless you have a shock absorber oil leak or excessive bottoming even after adjusting the suspension, there's not point rebuilding, once replacing is the option. Try stiffening your suspension and see if it helps.

Good luck.

Cheers!
VJ
 

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ya know -- it's funny because I woke up the other night thinking about this thread...

and it suddenly occurred to me that, if his gas charge leaked out somehow,

the shock could then cavitate and cause a worthless AF condition...

because it would then exist in a perpetual condition of trying to damp foam.

If he had a friend with a crank-based shock dyno and he viewed the force diagram as a continuous circular plot...

just past TDC (of the dyno chart), when the shock is supposed to be slowing down, the force plot would continue to rise.

Right, because the compressed emulsion condition would cause positive flow to persist longer.

Anyway... it's just a thot.
 

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So I thot you guys might get a kick outta this:

Here's an example of what I was trying to say... because I realize sometimes words alone just don't do [justice, in general].

These two plots are from two different forks; however, both are options for the same vehicle.
The light colored plot is a pretty standard representation of generally good pressure balance --
only a very slight trend toward continued force rise in the upper right quadrant of the cyclic pattern, suggesting some minor fluid gassing. But nothing severe.

But now look at the darker colored plot.

In the zone designated 'A', the force plot continues to rise, even though the fork is currently slowing down toward the position of maximum compression.
The reason this is currently happening is because the accumulator of the fork is being over-driven as the fork's main piston fluid-flow stalls, turning to a semi-gaseous state (on its downstream side).

Yes, the gas force was very carefully tested and deducted prior to running either fork on the dyno at higher speed.

Finally, look at the zone designated 'B', for the darker colored plot.
The fork's piston is now moving backward, through the emulsion it just created.
As a consequence, the accrued force is severely lagging behind the relative change in piston velocity, then it suddenly ramps back up once the majority of the gaseous emulsion has passed back through the rebound piston.

This particular fork had a tendency to 'blow through the stroke' when out on the track; all because it was continually gassing the fork oil; ergo, no damping.

It was also 'beating the heck outta' the rider, because it was 'kicking back' at him so hard on rebound; ergo, no damping.

The dyno cleared up the matter of what/why, without disassembly, then we yanked it apart and corrected the real problem. It was a very cool day, because 3 people I know were suddenly "much more better".

Oh yeah -- the pic:

F vs D plot 001.jpg
 

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What a very strange reply/advice?
On what do you base this?
What do you mean by 'stiffening' if the OP clearly stated the deterioration of the shock was gradually over the past 6 months and he cracked up the preload by 3 klicks without the desired effect?
If, like you perhaps, you have the cash to through around I would advise fitting an Öhlins, K-Teck or Bitubo fully adjustable shock.
Cracking can happen to anyone KTMasean. It can perhaps be an isolated incident. Let me share what happened to me, I had a leaky rear shock, the company replaced it for free, how can you rebuild a leaky shock. If you have a faulty spring that has lost its temper, perhaps you can re-temper and re-use. But a shock that's leaky, it isn't worth the labor, time and what not to be repairing in the hope it doesn't re-surface. The newer 2015+ shocks have shrouds which help prevent them exhaust heat and wheel muck, hence improved life. In my case, it's holding up well.

Cheers!
VJ
 
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