Stock Muffler Question....for a 2003

khibb · September 7th, 2020, 07:28 PM

Hi All,

New to the group and just posted up about the 2003 that I've just acquired. Excited to learn more about the bike from the crew here.

Quick question, The PO must have removed the end caps from the stock mufflers at some point. I want to return the mufflers to stock form and quiet them down a bit so I'm going to make end caps. Can anyone who has stock end caps measure the side of the center hole in the stock cap so I can get the correct size?

Thanks so much and we'll see how this goes.

Triple Jim · September 7th, 2020, 07:54 PM

It's not just an end cap. It looks like a tube is missing too. There should be a tube about 3/4" in diameter that extends 6 or 8 inches in, with perforations in the rear part. If you can replace that and plug the four rivet holes you'll be back to stock I think, but you need to try and find one to copy if you can.

You put this in the 2008-2012 Ninja 250R Tech Talk section, so maybe a mod can move it for you.

DannoXYZ · September 7th, 2020, 11:07 PM

Here’s what factory end-cap looks like.

Looks like they drilled out two of holes way over sized on yours. To fit same-sized rivets all around, you may want to tack-weld/braze some washers over huge holes to reduce ID to same as others so same rivets can be used all around.

The ridge/fold in centre is to make cap more rigid so centre tube doesn’t wiggle around. Which would end up causing cap to crack over time. You can replicate that by welding on reinforcement washer onto cap on outside or inside. Reinforcement should contact both inner tubing and cap.

Another function of ridge at end-cap is to allow flow-reversal from outer-chamber through gap between inner tube and outer one. Then exhaust reverses one final time into centre of inner tube and out end-cap. Without that ridge for reversal, you can have convex cap that seals against outside edge. Space it away from existing end with some spacers over rivet holes.

DannoXYZ · September 7th, 2020, 11:38 PM

You’ll want inner tube to reach deep into muffler with perforations at far end with closed tube.

Perhaps easiest to get pre-made universal unit and modify to fit. Slice off mounting ring to result with flat cap that’ll fit right into end of muffler.

https://www.ebay.com/i/222190529373

As mentioned, inner tube should be about 20mm to give exhaust room to flow forward to end with perforations.

Triple Jim · September 8th, 2020, 05:44 AM

Quote:

Originally Posted by DannoXYZ

You’ll want inner tube to reach deep into muffler with perforations at far end with closed tube.

That's not what my '05 has. Mine has an open ended 3/4" tube that reaches within about an inch or so of the first internal baffle plate. The tube has perforations in about its near half, but is plain for the far half, opposite of what your photo shows. The perforations are numerous and smaller than in your photo.

Also I don't see how the bulge in the plate could allow any flow reversal, based on the OP's photo of what's under it. It's just blocking the space between the large tube in his photo and the 3/4" tube.

I have no idea if this changed over the years. My mufflers are nice and quiet though.

Ideally it would be good to find some giveaway crash damaged mufflers and swipe their plate-tube assemblies.

khibb · September 8th, 2020, 05:47 AM

DanoXYZ,

Thanks so much for this info! I clearly didn't realize that there was an entire assembly that slid in there. That makes a lot of sense based on baffles that I've swapped out on my Harley.

I'll check out the universal part that you linked and good catch on the 08-12 Tech Talk. How do we ask the Mods to move it?

Thanks again!

September 7th, 2020, 07:28 PM	#1
khibb ninjette.org newbie Name: Kent Location: Acton, MA Join Date: Aug 2020 Motorcycle(s): 2003 Ninja 250, Harley Sportster 1250 Posts: 6	Stock Muffler Question....for a 2003 Hi All, New to the group and just posted up about the 2003 that I've just acquired. Excited to learn more about the bike from the crew here. Quick question, The PO must have removed the end caps from the stock mufflers at some point. I want to return the mufflers to stock form and quiet them down a bit so I'm going to make end caps. Can anyone who has stock end caps measure the side of the center hole in the stock cap so I can get the correct size? Thanks so much and we'll see how this goes.

September 7th, 2020, 11:07 PM	#3
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	Here’s what factory end-cap looks like. Looks like they drilled out two of holes way over sized on yours. To fit same-sized rivets all around, you may want to tack-weld/braze some washers over huge holes to reduce ID to same as others so same rivets can be used all around. The ridge/fold in centre is to make cap more rigid so centre tube doesn’t wiggle around. Which would end up causing cap to crack over time. You can replicate that by welding on reinforcement washer onto cap on outside or inside. Reinforcement should contact both inner tubing and cap. Another function of ridge at end-cap is to allow flow-reversal from outer-chamber through gap between inner tube and outer one. Then exhaust reverses one final time into centre of inner tube and out end-cap. Without that ridge for reversal, you can have convex cap that seals against outside edge. Space it away from existing end with some spacers over rivet holes. Last futzed with by DannoXYZ; September 8th, 2020 at 12:15 AM.

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September 7th, 2020, 07:54 PM	#2
Triple Jim Guy Who Enjoys Riding Name: Jim Location: North Carolina Join Date: Jul 2016 Motorcycle(s): Ninja 250 Posts: A lot. MOTM - Oct '18, Aug '17, Aug '16	It's not just an end cap. It looks like a tube is missing too. There should be a tube about 3/4" in diameter that extends 6 or 8 inches in, with perforations in the rear part. If you can replace that and plug the four rivet holes you'll be back to stock I think, but you need to try and find one to copy if you can. You put this in the 2008-2012 Ninja 250R Tech Talk section, so maybe a mod can move it for you.

September 7th, 2020, 11:38 PM	#4
DannoXYZ ninjette.org certified postwhore Name: AKA JacRyann Location: Mesa, AZ Join Date: Dec 2011 Motorcycle(s): CB125T CBR250R-MC19 CBR250RR-MC22 NSR350R-MC21 VF500F CBR600RR SFV650 VFR750F R1M ST1300PA Valkyrie-F6C Posts: A lot. MOTY - 2018, MOTM - Nov '17	You’ll want inner tube to reach deep into muffler with perforations at far end with closed tube. Perhaps easiest to get pre-made universal unit and modify to fit. Slice off mounting ring to result with flat cap that’ll fit right into end of muffler. https://www.ebay.com/i/222190529373 As mentioned, inner tube should be about 20mm to give exhaust room to flow forward to end with perforations.

September 8th, 2020, 05:47 AM	#6
khibb ninjette.org newbie Name: Kent Location: Acton, MA Join Date: Aug 2020 Motorcycle(s): 2003 Ninja 250, Harley Sportster 1250 Posts: 6	DanoXYZ, Thanks so much for this info! I clearly didn't realize that there was an entire assembly that slid in there. That makes a lot of sense based on baffles that I've swapped out on my Harley. I'll check out the universal part that you linked and good catch on the 08-12 Tech Talk. How do we ask the Mods to move it? Thanks again!