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breakwellmz

Is this a very restricted exhaust?

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Hi

 

Just out of interest it took the back end off my silencer and pulled out the baffle.(It`s a dual sport 300cc 4 stroke)

Is this particularly restricted? There don`t seen to be too many holes for the exhaust to get out! 

I definitely do NOT want a noisy bike or ANY loss in bottom end power but wonder if i could get any performance gain by making this less restrictive?

 

Cheers

Exhaust 003 (Small).jpg

Exhaust 001 (Small).jpg

Exhaust 002 (Small).jpg

Exhaust 004 (Small).jpg

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You will gain low end tq by opening up the quiet core/baffle not lose it as long as the jetting is right for the freeing flowing pipe. Every time I made a loud pipe quieter I lost bottom end power and every time I opened up a stock restricted muffler I gained bottom power.

I'd cut the end off the baffle here, if you want it even louder cut the baffle off shorter, the shorter that pipe the louder it will be.

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Hi

 

"Gain low end torque" sounds a very good opening to me! ☺️  

I`ll do that straight away. I have a range of pilot jets, mains and one more notch left on the slide needle as well.

Thank you.

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Cutting out that end plate will increase flow substantially, but will also increase noise by quite a bit.  Rather than going all in at once, you may want to try drilling a good sized hole in the end plate and try it out.  The larger the hole, the better the flow, and the louder it will get.  Experiment before going all the way and finding it it too loud.  Then you will have to find a welder to fix it.  

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Opening the muffler up will only make it noisy. You must do the air box, carb, jetting to get any gains. There is more to it than just chopping up a baffle. A proper performance exhauist is the way to go along with everything else. Air fuel in----exhaust out.

Make/Model/Year???

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Opening the muffler up will only make it noisy. You must do the air box, carb, jetting to get any gains. There is more to it than just chopping up a baffle. A proper performance exhauist is the way to go along with everything else. Air fuel in----exhaust out.
Make/Model/Year???
Gain huge powah with this one weird trick!20190125_084417.jpeg
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  • Haha 4

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If you find it too loud you can always  flatten the open end a bit where you cut it off.

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Make all those holes 1/4 inch then see how she feels. Clean air in always equals the stinky air out, so a larger main jet will also be needed to keep the stinky level the same. There is no way to avoid the increase in noise so chose what you want most, or just exercise some throttle restraint in sensitive areas.

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It'll be louder , but I don't think it's going to be as everyone thinks , the tube with the end cut off is all most quiet inserts are for aftermarket exhausts.

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Cutting off or adding a hole in that end plate is going to make it a lot louder since the sound can go straight through and out.

Try adding or enlarging the holes along the side first.  I doubt you will notice much difference unless you also check the jetting, but it may sound faster.

Edited by mbrick
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I would do 1/8th inch holes a few at a time.

 Be sure and get the next 3 main jet sizes larger.

You will need to rejet.

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6 hours ago, mbrick said:

Try adding or enlarging the holes along the side first.  I doubt you will notice much difference unless you also check the jetting, but it may sound faster.

That's what I would do. This, along with other free mods and proper jetting, you will probably feel a noticeable difference in power. It will be louder but I wouldn't think too much.

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With no other changes besides removing the baffle, the XR400 that I had got a big boost in low end power and snappiness.

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Thank you all guys.

I think i will go the route of opening out the current holes in stages to see how it goes/sounds, the baffle can be out, drilled and back in again in no time.

 

Cheers

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If you haven't already started cutting/drilling, I'd suggest first getting some jets and figuring out what you'd need to do to the airbox.  Then as a first test, try just running with the baffle completely removed and the airbox as open as it will get without permanent mods.  My wife's CRF230F had a cork in the pipe and a plate in the airbox that both needed to be removed. And a few bikes also have an exhaust restricter between the head and pipe.  So check for that as well.  You will need to re-jet for fully un-corked.  And usually the manufacturer or some decent online sources can tell you what jet to use in that case.

The reason I suggest this is you want to know what the worst (best?) case is before doing anything you can't easily undo.  You may find the bike is quite nice fully un-corked, and that's a state you can revert to stock easily.

Edited by DirtAndBass

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Hi

Thanks for your input and i`ve not cut or drilled anything yet.

Just back in from having a poke and a prod as well as taking a couple of photos.

Here is the inlet to the airbox, it has an area of 6 x 1 inches, there are no unnecessary restrictions between it and carb but no room for scope either i don`t think. Perhaps this post should now be " Is this a very restrictive inlet?" 

I did start it with baffle out but end cap on, it settled down to a loud idle and became VERY LOUD when the throttle was opened! (There is a church graveyard behind me and i`m sure i disturbed some of the residents!)

Poking down the exhaust there doesn`t seem to be any obstruction between piston and baffle.

It does have a VERY long header pipe which i understand promotes torque at lower engine speeds which is what i want. 

This is a South African designed and built bike and i get the impression that they are the other end of the spectrum when it comes to choking the life out of an engine compared to some US states! (300cc KLX clone with a claimed 28bhp at 8500)

Any advice much appreciated.

 

Cheers

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