Finally Making the WB R4 Sound Check below 100

2 replies to this topic
  • John_Lorenz

Posted July 20, 2002 - 12:19 PM


Ok her is the Short Version. I am still working on the long and will post a link to it, so not to take up space.

Bottom line is do this mod and the R4 Wb Exhaust will settle in at 100 db or less 98 if you do me secret patch prio to the test..

Here is the Mod,
Cut Accross 4 holes and bend downward into the Baffle.Remeber the Bend must be so the Exhaust flow is flowing into the new arch, I have about 28 or 30 divits made, I would say more then 28 28 is the min..
Posted Image
View from Inside
Posted Image
Wrap one layer of stainless steel wool grade 1, I have 3 pieces of wool cut to size here, they overlap about 1 inch.
Posted Image
Posted Image
Wrap the packing one full wqrap, cutting away the excess, DO NOT OVER LAP butt the ends together, it needs to be loose inside.
Posted Image
Posted Image
Once you have all the packing in and around, rivit the end back on and try it out.

Here is one last addition
if you fail (You Wont) bring it back to the truck and add the following to the end .
The Secret to 98db
Posted Image

Shred a small peice 2 -3 layers of packing and place into the spark arrester cone, you should just see sunlite if you hold it against the sun. Hold it in place with a small wire mesh.

Ride real slow to the sound chk booth, then check.

Hey if it dont work for you then what the heck you still have to by a new pipe anyway.

This has worked on my sns 250 and me 426

I put the secret in prior to the first test at 98 then the second without at 100...
I will post better details In soon.. I have alot of pics and ifo to put in...If you want all the pics wait until Sunday Eve, its taking time to format
Good luck

Oh ya if you ruin the Baffle dont worry you can get one for WB at I think 10 bucks

[ July 20, 2002: Message edited by: E.G.O.**** ]

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • Guest_mxrider426_*

Posted July 20, 2002 - 08:52 PM


Did you loose a noticable amount of power after chopping up your pipe like that? How many db's was the pipe before you modified it?

  • John_Lorenz

Posted July 21, 2002 - 06:30 AM


They tagged me at 107 the first attempt (Stock)

I modified a little and repacked

2nd was 104

I modified again and repacked

3rd = 101.9

I then choppd the heck ut of it and did asyou see in the pics

98db Passed

the had me test again at 5000 rpm as opposed to 4500 99db

then at 7500 = 101 db

I then wacked the throttle and It peeked at 102.2.

No power loss at all, In fact I soundly trounced a ktm520 again. Well at least the rider could not keep up..

Related Content


yz250x vs 450 4t comparisons (preferably desert riding) needed by JakeNorthrupYZ450F

Dirt Bike   Make / Model Specific   Yamaha   Yamaha 2-Stroke
  • 9 replies

Megabomb Fitment by 288yz450

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply

Should I buy this bike? help....... by Numsa Hul

Dirt Bike   General Dirt Bike Forums   What bike should I buy?
  • * * * * *
  • 10 replies
WR Camshaft Swap Info - last post by jamesm113

WR Camshaft Swap Info

  • 0 replies

Snake pit oct 30th by The Anvil

Dirt Bike   Dirt Bike Regional Discussion   California
  • Hot  293 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.