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can somebody tell if i modified my exhaust right?

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i know it has been talked a lot in here and i read a lot pages myself also,but i end to be confused...

i have a 2002 xr 400 and my exhaust is this:HM KCY A1

i try to apply gordon s mod,step by step and i d like to know if i have done it right,so i post my exhaust s picture

IMG_20140603_152718.jpg

IMG_20140603_152733.jpg

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With the "A1" version, I don't know if drilling would do anything or not. That version you can actually pull out the entire assembly you drilled and still keep the spark aresstor functioning. The A1 also has a smaller opening with the insert in than the A2 does. Here is a pic of an A1 and A2 side by side. I do not have the insert in the A1 so the opening is much larger and the A2 I show is drilled out with about 5 holes. I like the A1 with open end better myself but a lot of people feel it is to loud that way.

 

A2 on left / A1 on without insert on right

006-1.jpg

 

Side view, same orientation

005-1.jpg

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With the "A1" version, I don't know if drilling would do anything or not. That version you can actually pull out the entire assembly you drilled and still keep the spark aresstor functioning. The A1 also has a smaller opening with the insert in than the A2 does. Here is a pic of an A1 and A2 side by side. I do not have the insert in the A1 so the opening is much larger and the A2 I show is drilled out with about 5 holes. I like the A1 with open end better myself but a lot of people feel it is to loud that way.

 

A2 on left / A1 on without insert on right

006-1.jpg

 

Side view, same orientation

005-1.jpg

i feel too that if A1 is fully opened is really loud.well i will try it this afternoon,hear how it sounds with the 3 holes i made,see how the bike performs(i have removed my snorkel,got a Twin air filter and the bike was running great when the exhaust was full opened).

in a video i saw(for xr250 though) another guy suggests the holes to be made like this in the picture.could this work in my exhaust?

vlcsnap-2014-06-03-16h06m44s143.png

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another guy suggests the holes to be made like this in the picture.could this work in my exhaust?

That bypasses the spark arrestor.

Edited by Trailryder42

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i tried the bike with the insert in this afternoon.it is too silent for my taste!and the the real  case is that the bike is not as fast and snappy as it was with the insert out so decision is without insert for sure!

if anyone has another suggestion how to make the exhaust a little bit quieter but without so much power loss,i would be glad to hear! :rolleyes:

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From my understanding of the Gordon mods you didn't drill the holes in the correct place. I drilled my A1 the same way that's shown in m'400's A2. 

I also did a Uni filter and removed the airbox lid, rebuilt my carb with 135 (one step richer) main jet. I only drilled 2 holes so far, but the bike is a little louder and runs a little stronger.

Aren't you at sea level? Maybe your carb isn't jetted correctly to begin with, too rich?

 

cheers

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. I drIlled my A1 the same way that's shown in m'400's A2. 

Can you provide a link on this?

And yes i am at sea level.

Thank you guys for helping!!

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If you or a friend has access to a lathe, you can get a pc. of aluminum rod stock and make a reducer for the A1 without the stock insert in. Use the same M4 scres to hold it in place.

 

It would be approx. 1.375" OD to fit into the A1. Make the ID approx. 1" to 1.0625" and make it the same length or just a little longer (important) than what is needed to go the entire length of the outlet pipe in the SA (maybe 3 or 4", can't remember for sure). Taper the interior end (or thin them out) that hang out some so they are not square. Drops a few decibels that way and the flow / power is much better when going through a single opening vs. a bunch of small holes.

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If you or a friend has access to a lathe, you can get a pc. of aluminum rod stock and make a reducer for the A1 without the stock insert in. Use the same M4 scres to hold it in place.

 

It would be approx. 1.375" OD to fit into the A1. Make the ID approx. 1" to 1.0625" and make it the same length or just a little longer (important) than what is needed to go the entire length of the outlet pipe in the SA (maybe 3 or 4", can't remember for sure). Taper the interior end (or thin them out) that hang out some so they are not square. Drops a few decibels that way and the flow / power is much better when going through a single opening vs. a bunch of small holes.

i do have access to a lathe(a friend of mine will do the job).what you mean by :1.375" OD?excuse me i don t get it..(don t know much about mods nor i am a mechanic type of guy)

do you have a pic of this or  video to see?if you can make it clearer to me,it would be fine.thanks a lot for the help and don t bother uploading something to explain,i don t want to steal your time :thumbsup:

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I'll try and remember to take a pic of mine when I get home. Basically, the A1 like I show on the pic I posted, has an outlet diameter of apprx. 1.375" or the same diameter as the insert you drilled. Let me see if I can make an approx. drawing with MS paint or something and post it.

 

Maybe this will help. The dimensions are approximate and should be made to match and work with what you actually have. You need to make it a custom fit for what it's going in. The first step is to remove the insert you drilled out so it looks like the A1 pic I posted with the big opening. The opening is approx. 34mm diameter (1.375 inches). You want to machine an ID of approx. 24-26mm (start small and increase gradually after testing for noise level desired). You can always take more off but you can't put it back once it's gone. I'll try and follow this up with a pic when I get home if you still need but hopefully this will give you an idea of what I'm talking about.

 

IMAG0376_zps42c33745.jpg

Edited by michigan400

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I'll try and remember to take a pic of mine when I get home. Basically, the A1 like I show on the pic I posted, has an outlet diameter of apprx. 1.375" or the same diameter as the insert you drilled. Let me see if I can make an approx. drawing with MS paint or something and post it.

 

Maybe this will help. The dimensions are approximate and should be made to match and work with what you actually have. You need to make it a custom fit for what it's going in. The first step is to remove the insert you drilled out so it looks like the A1 pic I posted with the big opening. The opening is approx. 34mm diameter (1.375 inches). You want to machine an ID of approx. 24-26mm (start small and increase gradually after testing for noise level desired). You can always take more off but you can't put it back once it's gone. I'll try and follow this up with a pic when I get home if you still need but hopefully this will give you an idea of what I'm talking about.

 

IMAG0376_zps42c33745.jpg

 

 

wow!that is help!i don t know how to thank you really for the great info :goofy: .

don t shoot me but i want to ask more.this piece is going to be like a cylinder with outside diameter 34mm and inside diameter 24mm,from one end to the other.do i got it right?and is gonna be as long as the OEM part?thanks again,please don t shoot me and if you can post a photo of your exhaust.

IMG_20140605_011105.jpg

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Yes, a cylinder.

 

Those dimensions are approximate, you need to take off the whole end cap and let the guy turning it measure it up for exact fitment. Make it tight enough that you have to work a little to get it in all the way. I was able to slid mine in by hand up to the last 15-20mm or so, then used a rubber mallet to lightly tap it in the rest of the way.

 

I would also suggest leaving a lip on the outside at the very end so it's impossible to push it all the way in. That way you also have something to grab on to if you need to remove it.

 

Make it the full length of the 34mm section on your end cap at minimum. A little longer is fine, just don't leave it short because that will make a step on the inside and the exhaust will actually make a whistling noise from square face and sharp corner. My 1st one was short and sounded like a bird chirping when the motor was running. I'll be working on the bike later after work and I'll take a pic. I got busy last night and couldn't get to it.

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Why not just use the earlier A1 insert?

you mean the original part?

 

at the moment i m going to try michigan400 suggestions and report back,of course i d like to  hear alternative solutions.

thanks@all!

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It's beat up from making it to tight and removing it but here is a couple pics. Hopefully your friend will do this for a couple beers, don't spend much on it. Good luck!

1402072302766.jpg

1402072325381.jpg

1402072337668.jpg

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Read the following link and you will get some insights into the XR400 and XR650R exhaust that very few people are aware of.  I posted the relevant material  on this thread under the name oldmanrip.  Long story short, the restrictions are not where you think they are.  Drilling holes in the tip (pea shooter) does almost nothing.

 

good luck

 

http://www.thumpertalk.com/topic/1076106-kevins-very-quick-engine-hop-up/

Edited by oldmanrip
  • Like 1

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Read the following link and you will get some insights into the XR400 and XR650R exhaust that very people are aware of.  I posted the relevant material  on this thread under the name oldmanrip.  Long story short, the restrictions are not where you think they are.  Drilling holes in the tip (pea shooter) does almost nothing.

 

good luck

 

http://www.thumpertalk.com/topic/1076106-kevins-very-quick-engine-hop-up/

Now that's an interesting and helpful post, thanks very much. I've got an '02 250R with an A1 spark arrestor, have done the basic Gordon mods (2 holes as in michigan400's A2 tip, Uni filter, carb rebuild with 135 main jet and replaced the spark cap resistor with a piece of solid copper) and was planning to clean up the welds in the header next. I would have removed the exhaust tip already to see about performance gains and loudness but the previous owner stripped that dam torx bolt. I guess next rainy day I need to drill it out and now considering a custom made tip too. Any suggestions?

 

cheers

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That e-bay exhaust piece is way too loud. Too loud is too loud and causes problems here in the US.  The stock piece modded properly works well, has good tone and  still produces great low end torque which is the greatest asset an XR4 has. 

  • Like 1

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