TO: Nyroc / Everyone Else,

I'm about 1 week away from doing the Nyroc Mod to my P650 exhaust, and I am planning to do a few things different than your original plans for the Nyroc Exhaust Mod. I would like your opinion/constructive criticism of my planned changes.

First, I am going to use 1/2 inch holes instead of 3/8 inch holes for more air flow, but many folks have already done this, so its not novel.

Second, I plan to space out the 6 holes a little differently. I plan to drill 2 holes side by side near the 12 o'clock position, 2 holes side by side near the 6 o'clock position, then drill 1 hole at the 3 o'clock and 1 hole at the 9 o'clock position. I'm thinking that it may be best to have 2 holes near the top and 2 holes near the bottom of the baffles so as to free up the air flow coming into the muffler from the 2 intake pipes -- which are located one on top of the other near the 12 and 6 o'clock positions.

Third, I plan to fabricate a new baffle/spark arrestor using 2" (or 1.75") diameter pipe by drilling holes into it and wrapping it with a stainless steel mesh...it will be the same design as stock baffle/spark arrestor, only larger. This fabricated baffle/spark arrestor will then be welded in placed of the old one (attached to end cap and mounted at a 45 degree angle).

What do you think of these changes??? I'm hoping it will be freer flowing and still relatively quiet.

 

Although the muffler must be very different on my 360 --I did a sort of Nyroc muffler mod and drilled out my spark arrestor and tailpipe ann replaced with a copper inch and a half elbow from Lowes. Bike sounds great and noise is blown into the ground. Next time I cut back of muffler off (again) I am going to try to fabricate some kind of spark arrestor into my mods.

 

The stock spark arrestor is a little more than that. I'm not sure what makes a spark arrestor a working arrestor. The stock arrestor is about a 2 inch dia. tube roughly 4 or 5 inches long with a 1 1/2 inch preforated steel tube inside of the 2 inch tube. Packed in between the walls of the tubes is some sort of material. I made the mistake of cutting mine out so that I would have a little more air flow but now I'm illegal and can't ride certain places where a spark arrestor is required.

 

RebelDS,
Interesting! So you are saying that the small perforated 1.5" tube (which is about 4 or 5 inches long) is totally SURROUNDED by a solid (no holes) 2" tube that is also about 4 or 5 inches long? I didn't realize that.

If what you said is true about the 2" tube surrounding the 1.5" perforated tube...perhaps I can simply cut and remove both the 1.5" and 2" pipes BEFORE I cut into the weld around the outside of the end cap and then cut holes into the 2" pipe (to make it perforated) and wrap it with wire mesh. That way I can reuse the 2" pipe and discard the old peforated 1.5" pipe.

Also, I could add a 2.5" solid pipe and weld it so its surrounding the 2" (newly perforated) pipe to mimick the original design. What do you think of this idea?

 

The packing material at the end is for reducing noise. It is not a spark arrestor. It can't stop all sparks by itself. Any forest ranger that just looks for that part of your muffler is up in the night.

The spark arrestor is the maze of baffles that sparks must travel thru to get out. They are heavier than air and if the air has to change direction, the sparks hit something and go out before leaving the muffler.

The entire muffler was sent by kawasaki to be tested for approval by hooking it onto a machine that blows sparks into it. If you modify it at all, technically your muffler does not meet USFS approval anymore.

Mikey, good job on the muffler Ideas. The 1/2 holes will make it louder and perform better. The 12 o'clock 6 o'clock stuff probably will make no difference IMO, once the air gets out of the main tubes the position of the holes won't really help or hurt. Are you interested in trying something funny? Try many smaller holes of different sizes. 6 1/4" holes, 6 5/16" holes, 3 3/8" holes. I wonder if that would cut the sound more, if that would make the air pressure wave go slower through the smaller holes and cause attenuation. I wish I had tried that.

However, if you make a good noise reducer on the end, hopefully that will make the noise go down and you will still have the power that the other people that drilled 1/2 inch holes do.

Please send me photos if you think the noise reducer tip worked out well.

 

Mikey, I wish I could draw a picture on here, but I can't. If you look at the back of your muffler, you will see where the exhaust comes out of a 1.5" pipe (inner pipe) and that pipe is inside of a 2" pipe (outer pipe). Those two pipes extend inside the muffler about 4 or 5 inches. On the inside end, the outer pipe tapers down at the end and connects to the inner pipe. So to remove the inner pipe, you have to take some sort of saw and cut from outside of the muffler in between the two pipes, going all the way around the inside circumference of the outer pipe. Then you have to cut the cap off of the muffler. Then you cut through the baffler at the inside end right before the outer pipe tapers down to weld to the inner pipe. Then the inner pipe can be pulled out (with the packing maybe) and you'll be left with the outer pipe for the exhaust pipe. I'm not sure if any of that makes any sense.

When I did mine, I didn't have a saw that would cut around the inner circumference of the outer pipe (only had a big blade reciprocating saw) so I took a 1/4" drill bit and drilled holes all the way around between the inner pipe and the outer pipe. I cut the inside end off and used a screw driver to pick all of that packing out. Now I still have an inner pipe, but also exhaust can go out between the inner pipe and the outer pipe through all of those little 1/4" holes I drilled. It probably doesn't make sense what I did, but it seemed to work. Now I have a better sound and less restrictive flow.

 

RebelDS,
Thanx for the detailed descriptions! Now I can picture the inner and outer tubes in my head.

What I might try is to cut out the perforated inner tube while leaving the solid outer tube. Once I carefully hack off the end cap from the body of the muffler, I can then drill many small holes in the outer tube so it will be perforated like the inner tube was. Then I might wrap the entire outer tube in a stainless steel mesh (to make this outer tube into a home-made spark arrestor) and then reweld the end cap to the muffler (after drilling six 1/2 inch holes on the inside baffles of the muffler).

Right now, I'm not sure if its worth trying to weld a new 2.5" solid pipe onto the end pipe so as to SURROUND the 2" tube. If I did this plus add packing between these two tubes, it would closely mimick the design of the original (smaller) piece. While it seems like adding a new 2.5" solid pipe should make the muffler quieter, it would be at the expense of restricting the air flow going thru the end cap much more so than just having a 2" perforated pipe with steel mesh. I guess I'll have to think about that.

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

Nyroc,
FYI: I just finished with my Nyroc Modded muffler this morning (the hi-heat paint is drying on it as I type this message).

I ended up drilling 2 side by side holes (each hole was 1/2 inch wide) on top and 2 more side by side holes on bottom (all 4 were directly in line with the 2 head pipes coming into the front of the muffler).

Also, I removed the smaller (perforated) tube from the endcap while leaving in the larger (2" diameter) pipe intact. My thinking was this 2" pipe is good to keep because its pointed down at a 45 degree angle (like the original smaller pipe was) and this will help move the sound down towards the ground. I drilled about 150 to 200 tiny holes into the 2" pipe so that air could pass thru it from the underside of this angled pipe.

Also, I mounted a stainless steel wire mesh to the inside of this 2" pipe so that it would act like a home-made spark arrestor and also keep stuff out of my muffler (like small sticks, small rocks or whatever floats in the water where I ride). I had a HECK OF A TIME trying to find a stainless steel wire mesh. They don't sell it ANYWHERE near my house as most wire mesh is now sold as aluminum, brass or copper. I checked everywhere(auto parts, bbq pitt retail stores, arts and crafts places, Home Depot, Lowes, Welding and Fab shops)! I ended up using a 3" diameter Kitchen Sink Strainer piece that is supposed to mounted over the drain in the sink. They sell it at Lowes for $2 or $3 and its cone shaped (perfect!).

BTW, I took some pics during the process so you can see my changes and I plan to send them to you after I get the pics developed and scanned into my PC. What is your e-mail address?

Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]

 

I sent you a PM. Email away.

 

UPDATE:
The custom spark arrestor screen and baffle that I have on my Nyroc Modded pipe paid off this weekend in a VERY MUDDY/WET cross-country race (a local race). The mud was very deep in some parts of the course and it splashed up into the end of my muffler (which now has a 2" diameter opening following my Nyroc Mod) and some of it caked at the bottom of this opening (about 1/2 inch thick or so). I also discovered some of the mud caked onto the screen that I installed inside the baffle to act as a home-made spark arrestor and barrier to keep objects from going into my muffler. That tells me that without having the 2" baffle and screen, I would have likely gotten mud into my muffler with no way to get most of it out! So I'm very happy that I installed the screen and retained the 2" baffle tube! Luckily, it was easy to clean out the mud -- by just running my finger on the screen after the mud dried on it, the mud just flaked right off!

PS - I took 1st place in the utility division and 1st place overall in the B class race (out of 17 quads - most of which were sport quads like Raptor, Preditor, z-400, 400ex). Its nice to have 4wd and mud tires in muddy conditions like that!


NYROC,
This weekend, I sent you 6 pics of my muffler. Let me know if you received them all.


Happy trails...[img]i/expressions/face-icon-small-smile.gif[/img]