Stock muffler performance mod?!

So I have been contemplating cutting apart my Exhaust to see if I can improve on it without spending big bucks for a aftermarket muffler... WHY? Because I am cheap and have had great luck in the past with some mods of my own.

First I have 3 Goals to accomplish -

Keep the stock look with performance improvements of an aftermarket muffler
Remove the Catalytic converter in case it ever does get plugged, and free up the exhaust flow restricted by the stock CAT.
Completely remove the Exup device in the exhaust tube... (it most likely will cause air disturbance and could just be another thing restricting the exhaust flow.)

In theory, I don't see why these wont improve power, speed and throttle response, but we will see...

So to start... the bike!


I removed the plastic cover on the exhaust, the 2 bolts holding the muffler on and the bolt clamped around the header pipe.
First thing to do... Cut the pipe at the pint it starts to expand.. that is where I expect to find the Catalytic converter.



Theres the CAT! looks pretty small actually!




Time to remove it!... 2 Minutes with the metal saw and wallah!


Looking into the muffler from the Cat end now cut open.. there is not much in there... just a baffle and around the corner I can feel with my hand a hole for the exhaust gasses to go through.


Side View


On the end with the muffler cap I drilled 2 holes about 5/16" to open up a stright flow abit more. No pics sorry....
Back up to the other end I need to now remove that damn exup valve... not as easy but a bit of grinding and hacking, it's out!






15 min. later I have a new piece of metal welded in place where the old Valve was


Clean it up a bit and it looks great and is now a straight through pipe with NO WORRY the exaust valve might choke the engine!!!


next to bolt back the pieces on the bike and tack weld them together so they fit later on


Time to weld the pieces all back together


Now to use my new green backs and clean up my messy quick welds! :)




Put the exhaust back on my bike and take her for a spin to see if there is any noticeable difference... (Right now I am not sure... I am slightly pessimistic thinking it wont do much but I could be wrong)

All back together and it looks like stock... cant even tell unless you know to look closely for the exup valve and find it missing!
You can see the area where the exup valve was, but I think it looks just fine as is now for looks





So... the true test... I started it up, let it idle for a few minutes and took it on a nice ride around town trying to stay as unbiased as possible to any gains or downfalls the mods may have had.

Right out of the driveway I noticed it sounded different... seemed a bit lower pitch... NOT LOUDER.. just a bit lower pitch... I got on it and got the front wheel up a bit... I noticed it did seem a bit louder when under heavy throttle but not anything near obnoxious or illegal sounding. lol.

I did not want to say this, but It definitely does have more mid and High end power. as for low end grunt... it feels the same but a slightly quicker throttle response I think.... I took it up on the high way and reached an indicated 86.4MPH on my GPS... It still felt light it had some left in it, but too many cars around to push it further...

To keep from getting a barrage of questions on mods, the mods and specs so far are -

AIS Removal
Flapper for air box is screwed down
K & N Filter with extra screen insert
Exup wires clipped
Harbor Freight diy windshield
Dunlop D606's
Klotz racing oil
13/43 Stock Gearing

So far, it seems like one of the best and Cheapest mods I have done so far!
Next week I get a fmf programmer as I am sure I am running a bit leaner now!

EXUP wires clipped?

What exactly did you do? What does "clipped" mean?


I love the stock exhaust modification, however I think I'd have left the EXUP on it for a bit just to see if the thing had any relative advantage for low end grunt.
(that's part of the theory as to why it's there)

Otherwise....NICE JOB!

Great job

motokid wrote:

EXUP wires clipped?

What exactly did you do? What does "clipped" mean?

I just cut the wires and put a 7.5k 1W resistor on them.... Used lots of Silicone and then taped it up out of sight... seems to work great... no CEL.

Nice work

Interesting to see approximate drawing of muffer internals. I don't think such a big holes in CAT can significant stop gasses. There are should be something else..

Cuted mine today on the same place and ... was dissapointed. Euro version has not the same muffler as US. My catalyst is longer. I guess about 15 cm and it will be not easy to cut it. I used a screwdriver and a hammer to brake it. Tomorrow i'll try to ask help from local welder.
Do I need one more cut to drill some new holes inside?

hell0men wrote:

Cuted mine today on the same place and ... was dissapointed. Euro version has not the same muffler as US. My catalyst is longer. I guess about 15 cm and it will be not easy to cut it. I used a screwdriver and a hammer to brake it. Tomorrow i'll try to ask help from local welder.
Do I need one more cut to drill some new holes inside?

Awesome!
I still douth such CAT can affect gassed throughput its onlu heavy, may be there are some snake pipes at the end of the muffer, that prevent direct gasses out. Same seen at some EU Shadows. Did you cut another side of the muffer?

I wonder how he got there.

hell0men wrote:

I wonder how he got there.

У него америкосовская модель, там всё иначе :)

Hi got USA muffer model, they completely differ from EU...

The photo on rickramsey's site is what you see when you remove the end cap. Not sure if the Euro muffler looks different inside the end cap.

I did the same on mine... drilled about 6 or 7 holes (1/4" diameter). A noticeable crispness in throttle response without having touched settings on my FMF programmer.

skrew wrote:

hell0men wrote:

I wonder how he got there.

У него америкосовская модель, там всё иначе :)

Hi got USA muffer model, they completely differ from EU...

Будем потихоньку развивать русскоговорящее комьюнити.

Я тоже так решил что разные. В евро сложней система. Даже не знаю теперь оставлять эту или все таки разориться на FMF.

I guess they differ too. My cap is welded to can. It's not to easy to get inside. Thinking about FMF can again. Let's see what master will say.

Why?

MotoJunkie wrote:

The photo on rickramsey's site is what you see when you remove the end cap. Not sure if the Euro muffler looks different inside the end cap.

I did the same on mine... drilled about 6 or 7 holes (1/4" diameter). A noticeable crispness in throttle response without having touched settings on my FMF programmer.

Can I do this without a programmer? I have a foot long 1/2 inch drill bit, wondering if one or two holes with it would make a difference.

I bought this pipe and got another deal going if someone wants it.

https://wr250rforum.forumotion.com/t6653-stock-muffler-performance-mod

So Retto, how is the performance with the modded stock pipe?