Forum Main Tech Help/Race Shop FMF 4.1 RCT repacking tip request

FMF 4.1 RCT repacking tip request

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Neek

Vital MX member Neek 10722 Neek https://p.vitalmx.com/photos/users/10722/avatar/c50_98382000_1252912321.jpg?1294184848 https://www.vitalmx.com/community/Neek,10722/all 06/26/08 1 21 104

Posts: 125

Joined: 6/26/2008

Location: FRA

6/10/2018 11:55 PM

Hi Fellows,

My FMF RCT muffler needs repacking.
While dissassembling this bad boy yesterday, I noticed a metal fabric pressed/welded on the inner pipe as you can see below :

Photo
Photo

Should I remove this metal fabric or not ? I really want to clean all carbon deposit on the inner pipe, the bike is loud as hell. I am afraid not being able to put it back correctly since it seems pressed...

If I do not remove it, can I warm this metal fabric with blow torch to burn all carbon residue ?
Any suggestion with the packing material to reinstall ? Stick with FMF original stuff ?

Thank you guys !

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CarlinoJoeVideo

Vital MX member CarlinoJoeVideo 41118 CarlinoJoeVideo https://p.vitalmx.com/photos/users/41118/avatar/c50_jessy1_1471467436.jpg?1471466703 https://www.vitalmx.com/community/CarlinoJoeVideo,41118/all 11/30/13 17 53 https://www.vitalmx.com/community/CarlinoJoeVideo,41118/setup 130 6590 53 5 2

Posts: 6720

Joined: 11/30/2013

Location: Portland/Los Angeles, CA USA

6/11/2018 4:49 AM

Is there blockage on the inner pipe? I’ve never had to clean that out. Just leave that metal wrap and use the new packing, should be all it needs.

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Premix

Vital MX member Premix 41619 Premix https://p.vitalmx.com/photos/users/41619/avatar/c50_image_1407289457.jpg?1407288819 https://www.vitalmx.com/community/Premix,41619/all 01/05/14 1 https://www.vitalmx.com/community/Premix,41619/setup 50 1361 2

Posts: 1411

Joined: 1/5/2014

Location: AS, USA

6/11/2018 5:00 AM

Leave it on. Wrap your choice around the outside.

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Neek

Vital MX member Neek 10722 Neek https://p.vitalmx.com/photos/users/10722/avatar/c50_98382000_1252912321.jpg?1294184848 https://www.vitalmx.com/community/Neek,10722/all 06/26/08 1 21 104

Posts: 125

Joined: 6/26/2008

Location: FRA

6/11/2018 5:20 AM

CarlinoJoeVideo wrote:

Is there blockage on the inner pipe? I’ve never had to clean that out. Just leave that metal wrap and use the new packing, should be all it needs.

By lighting the inner pipe, I can see many holes obstructed with carbon residue...
That's why I'd like to remove this metal whool but I think my packing will burn faster if I cannot put it back like it is.

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Neek

Vital MX member Neek 10722 Neek https://p.vitalmx.com/photos/users/10722/avatar/c50_98382000_1252912321.jpg?1294184848 https://www.vitalmx.com/community/Neek,10722/all 06/26/08 1 21 104

Posts: 125

Joined: 6/26/2008

Location: FRA

11/9/2018 4:25 AM

Quick update on the repacking.

I kept the metal whool on the inner holed pipe and packed with FMF packing kit, strictly followed the advises from FMF.
Bike is quite loud, it was 117DB at the tech inspection during my last race and officials almost clipped me for the day...

I'll remove this whool, clean the holed pipe and wire it back.
Any advise regarding that ?

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swtwtwtw

Vital MX member swtwtwtw 9808 swtwtwtw https://p.vitalmx.com/photos/users/9808/avatar/c50_IMG_20180213_174109_497_1519139052.jpg?1519138744 https://www.vitalmx.com/community/swtwtwtw,9808/all 04/16/08 3 44 1200 70

Posts: 1245

Joined: 4/16/2008

Location: Apple Valley, CA USA

11/9/2018 3:25 PM

Use the spark arrester insert it’ll silence it a few decibels. You could run a hone thru the pipe to remove most of the carbon

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Motofinne

Vital MX member Motofinne 41595 Motofinne https://p.vitalmx.com/photos/users/41595/avatar/c50_JP_Purtilo20200830_BM0I161720200830_1605809939.jpg?1605809255 https://www.vitalmx.com/community/Motofinne,41595/all 01/04/14 3 https://www.vitalmx.com/community/Motofinne,41595/setup 100 9088 14

Posts: 9188

Joined: 1/4/2014

Location: FIN

11/10/2018 2:52 AM
Edited Date/Time: 11/10/2018 2:57 AM

I have no real advice to you but i'll tell you my experience with FMF and sound problems.

I had the 4.1 (stainless steel) system on my 2014 SXF 450 and there was no way that i was able to get it under the sound requirements in the Finnish races (FIM rules). I tried everything to get it under the limit but i had to go back to the stock pipe.

A friend of mine that only rides for fun got the titanium 4.1 system for his 2018 YZF 450 and the moment i heard the bike i said to him that there is absolutely no way that he would pass the sound tests in a race with that exhaust. I have never heard a louder bike in my life.

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nascarnate326

Vital MX member nascarnate326 44900 nascarnate326 https://p.vitalmx.com/photos/users/44900/avatar/c50_bliss_1486915553.jpg?1486914598 https://www.vitalmx.com/community/nascarnate326,44900/all 11/03/14 54 2831 6 1

Posts: 2886

Joined: 11/3/2014

Location: Charlotte, MI USA

11/12/2018 5:38 PM

Motofinne wrote:

I have no real advice to you but i'll tell you my experience with FMF and sound problems.

I had the 4.1 (stainless steel) system on my 2014 SXF 450 and there was no way that i was able to get it under the sound requirements in the Finnish races (FIM rules). I tried everything to get it under the limit but i had to go back to the stock pipe.

A friend of mine that only rides for fun got the titanium 4.1 system for his 2018 YZF 450 and the moment i heard the bike i said to him that there is absolutely no way that he would pass the sound tests in a race with that exhaust. I have never heard a louder bike in my life.

You need to hear a Kx250f. Mine was loud stock and with the 4.1 it was crazy loud.

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