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Decat the 1290!

PostPosted: Mon Jul 21, 2014 9:23 am
by ktmguy
I got the spare cat box today thanks to Scotman623, much appreciated!

Got the angle grinder out and had a look how to proceed. Decided to cut along the weld so I can tig it up later without too much giving away.
Seems to be the right decision in after making the cut.
It is basically a double box so when you get the first part of it looks like this:
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After making the second cut all around again you need to drill out these 3 welds at the top middle with a 8mm drill.
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Result!
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This is how the gas flows. Black in trough the cat, Blue back from behind the baffle chamber via the 3 smaller pipes, red out towards the end can.
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Ran out of time for now and won't be able to do much this week.
Will have a think how to proceed from here to cut the unwanted bits out and create a smooth flow but retain some damping.
I'll keep you posted on the progress.

Re: Decat the 1290!

PostPosted: Mon Jul 21, 2014 10:26 am
by OZsuperduker
Thanks for the insight. Good to know what they did. Did this on a V4 and good gains were had. Not the best solution, but it did offer gains. The down sides were not enough back pressure and didn't perform as well as proper exhaust systems. Keen to see results on a twin. Finding many differences and I could be completely of course here

Re: Decat the 1290!

PostPosted: Mon Jul 21, 2014 10:26 am
by abc
What are you trying to do guy :?:

Re: Decat the 1290!

PostPosted: Mon Jul 21, 2014 10:35 am
by OZsuperduker
Stock look with e4 stamp I suspect? Otherwise beats me why you would bother with all the weight

Re: Decat the 1290!

PostPosted: Mon Jul 21, 2014 10:36 am
by ktmguy
abc wrote:What are you trying to do guy :?:


Cheap improvement for those who want it.
Might not be that easy as due to the double skin it will be a pain to modify.
See ho we go.

Re: Decat the 1290!

PostPosted: Mon Jul 21, 2014 10:37 am
by ktmguy
OZsuperduker wrote:Stock look with e4 stamp I suspect? Otherwise beats me why you would bother with all the weight


Not that heavy when the cat part is out.

Re: Decat the 1290!

PostPosted: Mon Jul 21, 2014 11:13 am
by abc
So if I understand correctly, its a decat with a resonator and a stock look that you are after?

Re: Decat the 1290!

PostPosted: Mon Jul 21, 2014 11:22 am
by Joe Biker
ktmguy wrote:
OZsuperduker wrote:Stock look with e4 stamp I suspect? Otherwise beats me why you would bother with all the weight


Not that heavy when the cat part is out.


personally i would just gut the whole inside
and weld it back up just like the akra system
the stock muffler should give you enuff
back pressure :twisted:

Re: Decat the 1290!

PostPosted: Mon Jul 21, 2014 6:13 pm
by Heipaal
My ImageImage :

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Cut off the 2 flages in red, lose the whole vessle and welt a pipe (yellow).....

Re: Decat the 1290!

PostPosted: Mon Jul 21, 2014 6:44 pm
by scotman623
Glad to see you finally got it, I mailed it out on July 9th.. Good Luck with what you are trying to accomplish. Scott

Re: Decat the 1290!

PostPosted: Mon Jul 21, 2014 9:07 pm
by jmann
Comrade Guy: Looks pretty similar to the arrangement that Scottsduke revealed on the 990. I also did that at one stage and eventually concluded that the amount of argon I'd used wasn't worth the effort. Still nice to know what's inside. It always amazes me how small that hole is that goes backwards. No wonder these bikes feel like they want to breath more freely from the factory.

Re: Decat the 1290!

PostPosted: Mon Jul 21, 2014 10:09 pm
by ktmguy
Joe Biker wrote:personally i would just gut the whole inside
and weld it back up just like the akra system
the stock muffler should give you enuff
back pressure :twisted:


The akra system has a big pot in the middle, where the cat is on the original, is a resonator.

Heipaal wrote:
Cut off the 2 flages in red, lose the whole vessle and welt a pipe (yellow).....


That was the last step I was going to take after the rest, will do it with a bend like the bodis. I do this as an experiment and we'll see what works the best.

jmann wrote:Comrade Guy: Looks pretty similar to the arrangement that Scottsduke revealed on the 990. I also did that at one stage and eventually concluded that the amount of argon I'd used wasn't worth the effort. Still nice to know what's inside. It always amazes me how small that hole is that goes backwards. No wonder these bikes feel like they want to breath more freely from the factory.


I don't pay that much for the argon here, $140 for a G size. Yes G size. Need to shop around though, the rent can be a burden but at $18 a month it's cheaper than smoking...

Re: Decat the 1290!

PostPosted: Tue Jul 22, 2014 12:55 am
by jmann
ktmguy wrote: ... but at $18 a month it's cheaper than smoking...


And a lot more useful :D

Re: Decat the 1290!

PostPosted: Tue Jul 22, 2014 2:06 am
by abc
I would be tempted to weld a piece of half round pipe between the flanges and weld another piece of perforate pipe to mate to the half round pipe. Then just gut the cavity and you have yourself a resonator chamber that looks stock. Just upgrade the can and map and you have a cheap complete system that supplies adequate back pressure so you keep the strong midrange. Keep us posted on your progress Guy.

Re: Decat the 1290!

PostPosted: Tue Jul 22, 2014 3:03 am
by ktmguy
abc wrote:I would be tempted to weld a piece of half round pipe between the flanges and weld another piece of perforate pipe to mate to the half round pipe. Then just gut the cavity and you have yourself a resonator chamber that looks stock. Just upgrade the can and map and you have a cheap complete system that supplies adequate back pressure so you keep the strong midrange. Keep us posted on your progress Guy.


I had a think about it last night and the plan so far is: Take the cap out and stick a 63mm perforated pipe where the cat is till the separation, fit a new plate there where the original is.
Insulate that part with stainless wool and exhaust padding. In the back cut the pipe flush with the wall and close it back up. The last section will be another chamber than.
The trouble part to make a quick fix is that the box is double wall with insulation between it, so welding on the inside skin will most likely burn something...
I have another idea but I need some perforated stainless sheet for that, anyone?? Only need a few pieces roughly 400 x 200mm. Unavailable local...

I doubt that I can do anymore on it this week. Tomorrow is 2x400km to the dealer and the rest of the week I need to make a gate in stainless or aluminium.

Re: Decat the 1290!

PostPosted: Sun Aug 17, 2014 9:07 am
by ktmguy
Next and final installment:
I only did this to prove a point and prevent others from making the same mistake!

All gutted!
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Mock up of the parts, idea is to insulate the top of the cat box to keep the swingarm cooler and to keep some noise damping. Also want to keep it simple.
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Tacked in.
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Stuffing the turkey.
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Welded shut.
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Answers to your questions:
Is it worth it?
No it's not unless you really want to keep the original box for legal purposes or so and load the akra map, otherwise forget it! Buy a Bodis instead!
Does it make more noise?
I compared with the original can and it does a bit but not much.
Does it go better?
It feels crisper.
Is it easy to do?
Again, not really! It is a mission to cut the pipes out as they are hardened due to the heat cycles in the cat, the top bit you can get to with the angle grinder but for the rest you need a dremel or airtool.
The box is made out of thin stainless so it is also not that easy to weld unless you are good. (I'm not BTW)

Anyone commenting that my welds are ugly, go and F yourself!! I only learned to TIG weld last year from http://www.weldingtipsandtricks.com Great site, thanks Jody!

Re: Decat the 1290!

PostPosted: Sun Aug 17, 2014 11:26 am
by abc
Guy,
Did you consider leaving it empty so it can act as a large resonator similar to the Akra Resonator. Then just run it into the stock can with centre baffle removed as a budget improvement. The Akro resonator chamber is basically and open chamber with a perforated half sectioned tube running along its length in the direction of the flow. Interesting mod you have completed though.

Re: Decat the 1290!

PostPosted: Mon Aug 18, 2014 2:19 am
by ktmguy
abc wrote:Guy,
Did you consider leaving it empty so it can act as a large resonator similar to the Akra Resonator. Then just run it into the stock can with centre baffle removed as a budget improvement. The Akro resonator chamber is basically and open chamber with a perforated half sectioned tube running along its length in the direction of the flow. Interesting mod you have completed though.


Yes I did think about that! Main reason why I didn't is the exit tube out, If you look closely that is the most restrictive part and also the smallest diameter.
Unless I change that all the rest is in vain.
No reason to go any further on this just for that alone.
Interesting exercise but pretty pointless performance wise, doesn't even sound better.

Re: Decat the 1290!

PostPosted: Wed Aug 20, 2014 1:15 am
by OZsuperduker
Thanks for your efforts on this Guy!

Re: Decat the 1290!

PostPosted: Sun Dec 28, 2014 12:38 am
by ktmguy

Re: Decat the 1290!

PostPosted: Fri Aug 21, 2015 8:11 am
by ktmguy
New prototype decat. Home made.
Car type resonator 2.5 inch diameter 9 inch long. http://trrautoparts.com.au/resonators-hot-dogs/hot-dog-resonator-mild-steel-sl09250p
2 x 63mm (2.5 inch) 90 degrees elbows in 304 stainless.
Cut flanges of original cat.

Sounds really good, not as noisy as bodis but with nice low rumble.
I didn't have black heatproof paint, I'll paint it in black when I take it off again.

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Re: Decat the 1290!

PostPosted: Fri Aug 21, 2015 12:23 pm
by HYPERMOTO
Looks a neat job KTMGUY.

I wonder how it would compare with the arrow version or similar? (volume wise).

Re: Decat the 1290!

PostPosted: Fri Aug 21, 2015 10:00 pm
by ktmguy
HYPERMOTO wrote:Looks a neat job KTMGUY.

I wonder how it would compare with the arrow version or similar? (volume wise).


A few things are different.
It is almost impossible to get the correct 57mm (2.25 inch) pipework here in Oz.
I can't even get the thin wall exhaust grade stainless here. In New Zealand I could just get that from the local muffler shop.
So I had to use 63mm (2.5 inch) stuff so the resonator is a fair bit bigger than the arrows.

I need to put it on the dyno to see what it does, might do that soon.
The seat of the pants dyno is a bit confused at the moment as balancing the throttle bodies made it much smoother so it feels slow but looking at the speedo it doesn't.
The speedo is also different due to replacing the rings, so all up need to recalibrate a bit.

Next ride I'll do a sound file.

Re: Decat the 1290!

PostPosted: Tue Nov 17, 2015 1:54 am
by tonyteeth
So would it be possible for me to bang out the honeycomb which I assume is located in the first large pipe going in (shown in your pic with the black arrow)? That honeycomb converter has to be restrictive. Thoughts?

Re: Decat the 1290!

PostPosted: Tue Nov 17, 2015 3:08 am
by ktmguy
tonyteeth wrote:So would it be possible for me to bang out the honeycomb which I assume is located in the first large pipe going in (shown in your pic with the black arrow)? That honeycomb converter has to be restrictive. Thoughts?


It's not the honeycomb (cat) itself that is restrictive, it's the labyrinth at the back.
Follow the arrows in the picture and it becomes clear.