Goats Belly (Catalytic Converter) Replacement

It is called several things but "it" is the canister under the center of your bike into which all exhaust pipes flow. Inside the canister is a catalyst that processes and cleans up the gasses your bike exhales while, at the same time, smothering any remnants of the great V-Twin sound so many of us enjoy.

You can replace the "Goats Belly" with aftermarket pipes which generally cost from $300 on up. If you're looking for "loud" then pipes are the route you should probably take. A nearly "cost free" alternative is gutting the Goats Belly. If, on the other hand you're just looking for a little bit of rumble at idle, an authoritative roar when hard on the throttle but a sound level no louder than stock (at least from the drivers perch) while cruising then read on. This is the modification you need. Some who've done this modification say they can feel a power increase. I haven't noticed any extra punch but the sound makes the project well worth the price and effort.

It all begins with the order of a replacement pipe from the friendly folks at Motorshop de Mammoet. The product? It's fondly known on this side of the big pond as the "Dutch Bypass" and it's available from this web page http://www.motorshopdemammoet.com/mammoet_specials.htm
You can order via fax or e-mail (use 2 messages to ensure security of your credit card number) through the number/address provided on the web page. Be certain to indicate whether you have a carburated or fuel injected Nomad. The pipes are slightly different. You'll be working with Marianne who's extremely helpful and will certainly be able to answer any questions that aren't covered here. The price? Well that might be a problem. In 2001 when I purchased mine they were $135. Toward the end of 2003 the same product was being quoted at $255. Maybe it's the exchange rate and pricing varies day to day. You'll have to check with the company for current pricing.

You'll also have a decision to make about gaskets. You "WILL" need new crush gaskets where the exhaust pipes connect with the cylinder heads. You can not get around this, not no way, not no how. They'll be about $6.00 each through your dealer. There are other places you can find them for half the price so look around a little if you'd like. You can even use the Harley Davidson gasket set which some perfer to the crush type. (photo here) The other gaskets are inside the "Goats Belly" and can be re-used. You have to be extremely careful extracting them (they tear easily) or you just order four new ones from your dealer. If I had it to do over again that's the way I'd go. Save yourself half an hour of pounding on pipe trying to get the things out, worrying all the while that you're going to ruin them. If you do, you're dead in the water without a bike to ride until the dealer can come up with a replacement. The part number (you'll need four) is: 11009-1865 for the carburated Nomad, for the F.I Nomad you'll need two 11009-1865 and two 11009-1667 gaskets. Please Note: There are two different part numbers for the FI. If you re-use your old gaskets, keep track which "ports" they come out of so you can put them back correctly in the bypass. Just remember "muffler outlet" or "header inlet".

Needed (and handy) tools:

  • 10, 12 and 14mm sockets (deep will work better)
  • socket wrench (breaker bar will be handy to break both bolts loose holding the goats belly to the bike)
  • Extension (makes removal of cylinder head cap nuts easier)
  • Rubber Mallet (for when you get tired of trying to wiggle the mufflers into their gaskets)
  • Chisel or old flat blade screwdriver (to open flanges of goats belly to remove gaskets if you're re-using them)
  • Hammer (to beat on the chisel or old screwdriver with)
  • Needle nose pliers (for removing old gaskets from goats belly)
  • Anti Seize compound or high temperature grease. I recommend the former because it won't smoke and stink when you fire the bike up. Anti Seize is available in tubes from every automotive outlet. You probably already have some on hand for replacing spark plugs (steel plugs in aluminum cylinder heads) right?

Ok, so much for "what you'll need". What follows is a combination of the instructions provided by Mammoth and items I'm adding to make installation go a little smoother (or at least give you a heads up what to watch for). I'll number the Mammoth instructions in blue, mine in red so you'll know the difference. In the end you'll have a great sounding Nomad that won't annoy the neighbors when you leave for work or on those long rides at O-dark-30 in the morning.

Ready to spend a couple of quality hours with your bike? Ok, lets roll!!

  1. De-mount the entire exhaust system
    1. The heat shields (chromed tin) are held on by hose clamps. Once loosened, slide these clamps toward the "end" of each shield and they'll come off easily. The long shield attached to the front exhaust pipe has three clamps. One at each end and one in the middle. The middle clamp slides "up."
  2. Remove the pipe clamps from the pre-muffler chamber (goat bladder)
    1. If you spend some time noting the orientation of the clamp bolts it could save you a lot of time later when you're trying to put the heat shields back on.
  3. Remove the bolts and make the opening of the clamp a bit wider (because the replacement pipe is a bit thicker)
  4. Before you screw the bolts back into the clamp, put some anti seize (or other high temp lubricant) on the inside of the bolt.
    1. The newly expanded clamps "might" need a little persuading with a pair of pliers or vice grips to pinch it together enough to get the bolt threading again. Don't cross thread these things. If you've put a little lubricant on the bolts they'll turn easily.
  5. If you are re-using the original gaskets Very carefully, remove them from the "goat bladder" or the exhaust pipe. This works more often than not. If not, you'll have to purchase 5 new gaskets from your Kawasaki dealer (part numbers noted above)
    1. Having someone hold the "Goats Bladder" while you whack a chisel (or screwdriver) with a hammer to make the opening slightly wider will make your task easier. Bending back the tabs just a little (we're not trying to ruin the thing here) will make it much easier to grab the gasket with needle nose players. Wiggle the gasket out of the hole by working around the edge and pulling. After about the third one you'll probably wish you'd just ordered new gaskets. For F.I bikes, keep track of where these gaskets are coming from. There are two that fit the muffler pipes and two that fit the exhaust pipes coming from the engine. There must be a difference, Kawasaki has two different part numbers for them. If you're living a truly charmed life, some, if not all of the gaskets will have simply slid out along with their respective pipes. I want you to start picking my lotto numbers.
  6. Mount the clamps and gaskets on and in the bypass pipes. Do this carefully! If you noted the clamp position before removing them from the "goats belly" refer to your notes and orient them the same way now.
  7. Put some anti seize on the ends of the exhaust pipes where they'll side into the gaskets and a bit inside the gaskets themselves.
  8. Now you're ready to start putting it all together. Mount the rear exhaust pipe to the cylinder head using a new crush gasket. (Don't tighten it down tight yet) Slide the appropriate port of the bypass pipe onto the pipe. Attach the bypass pipe to the underside of the bike using the original (right hand side) bolt that runs through a vibration damper.
    1. The flat face of the crush gasket goes toward the cylinder head, the crushable side toward the pipe. You might want to shoo any youngsters out of the garage while you're trying to turn the bolt into the mounting tab for the bypass pipe. If you're really skilled (lucky) the bolt and hole will line up no muss no fuss and the bolt won't try to cross thread itself. For the rest of us this, and one other part of the installation may require some creative verbiage.
  9. Now you can add the right side muffler. Same routine, a little anti seize compound on both the pipe and gasket (if you didn't already) and slide into place. Bolt up the muffler (but not tight yet).
  10. Slide the front exhaust pipe into the appropriate bypass pipe hole and mount to the front cylinder using a new crush gasket.
  11. Go over to the left side of your bike and slide the muffler pipe into the bypass. (you remembered to grease it up a little right?) Wiggle, wiggle wiggle till it slides home. Bolt up the muffler.
  12. Now wiggle things around, go to the rear of the bike and be sure mufflers are straight and level. Start tightening. Tighten your cylinder head cap nuts first and work your way down and back. Tighten each clamp (don't force it) and the bolt holding the bypass pipe in place.
  13. Time to put the tin back on.... A little anti seize on each clamp will make things easier several thousand miles down the road when you want to remove mufflers to pull the rear wheel.
    1. Remember that "creative verbiage" thing from above? Re-installing the heat shields could exercise your patience a little the first time you do it. The most difficult piece is the cover for the rear exhaust pipe. Here's help. Each piece has a small notch in the bottom. This indicates where the hose clamps will go when you slide everything into place. Especially helpful for the center clamp on the front exhaust pipe.
  14. Now start your bike, check for exhaust leaks and ride!


Additional tip from KenSW

I purchased 1 3/4" P clamps from JC Whitney. I used these to affix both pipes to the original goats belly mounting holes. All that was needed was a couple of long bolts, and I had to bend the P clamps to have the holes lines up. This eliminated ALL vibration that one typical gets when losing that central mounting point. It is the same cause of the vibration we sometimes hear about when the pipes are changed.

[Gadget Note: The clamps Ken purchased from JC Whitney are chrome and are in the "exhaust" section of their MC catalog. If you can forgo the chrome you can probably find the clamps at any hardware store.]

Where do I get one? Here is the JC Whitney Link or you may be able to find one at a hardware store
Ken's Installation Photo Here

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