The Goats Belly Pre-Muffler what's inside and why - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 25 (permalink) Old 12-10-2011, 02:01 PM Thread Starter
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The Goats Belly Pre-Muffler what's inside and why

Okay, so I've searched this forum and found no real answer to the above question, and lot's of speculation about sound deadening material and a cat converter being inside. No cut-away pictures that I could Google. Today I was at our local bike graveyard and spotted a mangled 2000 VN750. I offered the yard owner $10 bucks, he said it was worth $30 and I said I was just gonna cut the f'er up to look inside, he said BS, I said I'll do it right here right now, he said prove it and I'll charge you $10 bucks.

So I got the saw out of the truck and split it lengthwise across the weld. What's inside is a) on the left intake is a 9 inch pipe with a reverse gentle 90, this balances the exhaust pipe length from the rear cylinder to the front length and directs the gas flow back towards the right side outlet, b) there's a 2 inch stub on the right side for the front cyl that dumps straight into the chamber, and on the rear exit of both sides is a 2 " stub leading to the muffler clamps.

No packing, no cat converter or baffle plates like on the VN800 and beyond. Keep in mind this was on a 2000 model.

So the pre-muffler balances the exhaust lengths and the chamber provides an early pressure reduction before the exhaust hits the muffler baffles.

We were all laughing so hard at why I was doing this in the junk yard that I forgot to take at least a phone camera pic!

Now you should be able to understand why there IS a power loss when you de-goat, and you should be able to figure out why the carb mixture will be off and near impossible to balance without fiddling with all the jets and the slide vacuum ports, and you should be able to figure out why it's not a great idea even if you add an H-pipe which won't balance the exhaust path (but that's better than just what you see in the Verses, for sure!)

Turns out the Kawasaki engineers aren't as dumb as a redneck with a hacksaw.
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post #2 of 25 (permalink) Old 12-10-2011, 02:41 PM
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Thank You. It is worth $10.00. I was told by the Kaw Mechanic that this engine is built and carburated to run with the back presure that the stock exhaust has. It sounds like they have made every effort to balance the system. As a side note I really like this forum because of the knowledge that is available here.

Mcneuby

Last edited by Mcneuby; 12-10-2011 at 02:42 PM. Reason: spelling
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post #3 of 25 (permalink) Old 12-10-2011, 03:16 PM
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Originally Posted by Mcneuby View Post
Thank You. It is worth $10.00. I was told by the Kaw Mechanic that this engine is built and carburated to run with the back presure that the stock exhaust has. It sounds like they have made every effort to balance the system. As a side note I really like this forum because of the knowledge that is available here.

Mcneuby
My butt and my buddies who looked at the rear end of my bike a lot more often afterward says different,you will lose a little on the bottom end but with a set of right side exiting pipes you almost balance the length out.And since it was called a premuffler it does change the sound a little.

The carburetor balance and mixtures can be achieved with patience and more air pulls more fuel burned efficiently at a higher rate of speed thru any engine provided the AF mixture and ignition timing is correct makes more power.Period

And if there is so much knowledge here why do you ask one mechanic at a dealership(who often have no clue) about something several on here have already tried and used with success and then slap us all in the face with it

If you want to keep your bike stock ,fine,but don't try to convince us that it is best,when we have already found out different.if you want to leave it stock that's fine,we don't care ,it is yours to do with as you please,you don't have to justify it to us.But we have been there and done that and wanted better and found it.




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92 vn750(sold)
Current ride 05 1500 Classic FI
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post #4 of 25 (permalink) Old 12-10-2011, 05:08 PM
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Wow, I didn't mean to upset you.

When I first got my vn750 I took it to the dealer and had them look at it. Since then I found this forum. I guess I don't care to go any faster than the stock bike will go. If that is what you want to do that is fine. I have kept mine stock and am satisfied with it. Like you say you do as you want with yours and I will do as I want with mine. But the bike does run pretty well stock. This is a good sorce or any modifications that you may want to make as well as just keeping it running.

Mcneuby
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post #5 of 25 (permalink) Old 12-10-2011, 05:42 PM
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Quote:
Originally Posted by AlwaysOnTwo View Post
Okay, so I've searched this forum and found no real answer to the above question, and lot's of speculation about sound deadening material and a cat converter being inside. No cut-away pictures that I could Google. Today I was at our local bike graveyard and spotted a mangled 2000 VN750. I offered the yard owner $10 bucks, he said it was worth $30 and I said I was just gonna cut the f'er up to look inside, he said BS, I said I'll do it right here right now, he said prove it and I'll charge you $10 bucks.

So I got the saw out of the truck and split it lengthwise across the weld. What's inside is a) on the left intake is a 9 inch pipe with a reverse gentle 90, this balances the exhaust pipe length from the rear cylinder to the front length and directs the gas flow back towards the right side outlet, b) there's a 2 inch stub on the right side for the front cyl that dumps straight into the chamber, and on the rear exit of both sides is a 2 " stub leading to the muffler clamps.

No packing, no cat converter or baffle plates like on the VN800 and beyond. Keep in mind this was on a 2000 model.

So the pre-muffler balances the exhaust lengths and the chamber provides an early pressure reduction before the exhaust hits the muffler baffles.

We were all laughing so hard at why I was doing this in the junk yard that I forgot to take at least a phone camera pic!

Now you should be able to understand why there IS a power loss when you de-goat, and you should be able to figure out why the carb mixture will be off and near impossible to balance without fiddling with all the jets and the slide vacuum ports, and you should be able to figure out why it's not a great idea even if you add an H-pipe which won't balance the exhaust path (but that's better than just what you see in the Verses, for sure!)

Turns out the Kawasaki engineers aren't as dumb as a redneck with a hacksaw.
Glad someone finally did that. I had a pretty good idea that is how it worked, and why it was a bad idea to remove it with otherwise stock pipes. Maybe someone on here who is absolutely certain the goats belly is a bad thing and has removed theirs but still has it laying around somewhere will be nice enough to cut it open and post pictures. But from your description, it sound pretty clear how it works to me.

I have removed a lot of parts from my Vulcan, all the emissions crap, even the right front brake and the "decel" or "push" throttle cable, because IMO they were not necessary and actually counterproductive. But the goats belly stays, because I feel it is necessary to make the bike run right with stock pipes.

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
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post #6 of 25 (permalink) Old 12-10-2011, 05:43 PM
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Quote:
Originally Posted by Mcneuby View Post
When I first got my vn750 I took it to the dealer and had them look at it. Since then I found this forum. I guess I don't care to go any faster than the stock bike will go. If that is what you want to do that is fine. I have kept mine stock and am satisfied with it. Like you say you do as you want with yours and I will do as I want with mine. But the bike does run pretty well stock. This is a good sorce or any modifications that you may want to make as well as just keeping it running.

Mcneuby
My point exactly ,and you are right about them having plenty of power in stock form .I am one of those people who think good enough really never is,and do this not this ,you have good reason you have a bike,thats enough to make most

P.S.Sorry if I sounded harsh.




If you see it on my bike I did it
VROC#30324
92 vn750(sold)
Current ride 05 1500 Classic FI
lovin' the new scoot



Quote:
"When all is said and done,usually more is said than done" UNK
Click on one x and drag to the other to read between them.

Psalm 40:1...
XI waited patiently for the Lord; and he turned unto me, and heard my cry. X

Last edited by denny6006; 12-10-2011 at 05:47 PM.
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post #7 of 25 (permalink) Old 12-10-2011, 06:58 PM
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It's cool to know what's inside of that thing so thanks for gutting it. Figured it was something to balance out the ex. since even though its on there, the tails of the mufflers are still staggered. Probably would be a lot more if no GB was employed. I can understand both sides of the argument to mod or leave alone. I, like Denny and many others want a little more if it can be obtained reasonably. In my case, it may be the fact that I went from a 4 cylinder GS1100 to my Vulcan. The Vulcan is quick but that GS was a rocket. And if you weren't a decent sportbike, on a straightaway... you weren't touching that thing. I was afraid of it. Stupid fast it was.
Anyway, I think both views are legit. If you're happy and you know it, leave it alone. They do perform very well without anything changed. But if you're not 100% then hey, have at some mods, what the hell. Yeah maybe there's some data that proves the life of the bike will be shortened, all be it very little I'd say if properly cared for, but if you enjoy riding it more because it's got a lil' more spunk, DO IT. Have fun with your bike, period.

Dave

Mods:
Jetted, shaved & coastered
Home made under-tank single filter
Converted ACCT's to manual (thanks wib714)
Dual vac lines on petcock (my cure for ticking)
LED tail/plate lights
Relocated helmet lock to license plate

Added stuff:
Customized hard bags w/ lights
Chrome levers
Hellcat windscreen
LED running lights
Home made 'Vita-Volt' meter
Foot rests on engine guard
Tunes

Hmm....she was on the back when we left.... ??
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post #8 of 25 (permalink) Old 12-10-2011, 09:27 PM
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Quote:
Originally Posted by DavesVulster View Post
It's cool to know what's inside of that thing so thanks for gutting it. Figured it was something to balance out the ex. since even though its on there, the tails of the mufflers are still staggered. Probably would be a lot more if no GB was employed. ...
... Yeah maybe there's some data that proves the life of the bike will be shortened, all be it very little I'd say if properly cared for, but if you enjoy riding it more because it's got a lil' more spunk, DO IT. Have fun with your bike, period.
X2

I happen to really like the stock look of my bike, including the ears, but after some recent wrenching I want to pitch all the CA crap and shave the ears just to make working on it more enjoyable. I love the way it runs bone stock and love the way it feels in the turns with the new low bars but all the extra tubes that do almost nothing but get in the way have got to go! I'm pretty sure my bike will run cleaner if I enjoy wrenching on it and dialing it in more often without the EPA stuff.

BTW, I like the stock exhaust and the only reason I personally think I would take the GB off would be to remove the heat source under the stock R/R location. I'm not looking for more power... yet.
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post #9 of 25 (permalink) Old 12-11-2011, 12:43 PM
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Quote:
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X2

I happen to really like the stock look of my bike, including the ears, but after some recent wrenching I want to pitch all the CA crap and shave the ears just to make working on it more enjoyable. I love the way it runs bone stock and love the way it feels in the turns with the new low bars but all the extra tubes that do almost nothing but get in the way have got to go! I'm pretty sure my bike will run cleaner if I enjoy wrenching on it and dialing it in more often without the EPA stuff.

BTW, I like the stock exhaust and the only reason I personally think I would take the GB off would be to remove the heat source under the stock R/R location. I'm not looking for more power... yet.
I did remove all the CA evap crap and the complete air injection system form mine. But I have left the engine/intake/exhaust completely stock, other than going from ACCTs to MCCTs. I have never had any need to work on mine. I did remove the carbs twice, when I briefly installed aftermarket pipes, to rejet, then had to remove them again to change the jetting back after going back to stock pipes. Not exactly what I would call easy, but not that hard either. It seems many people try to remove and reinstall the carbs with the gas tank still in place, and that is virtually impossible. If you remove the tank, and tie the "surge tank" up so it can't keep falling down on you, you would be amazed at how easy it is to remove and reinstall the carbs. First completely remove the ducts that go from the carbs to the surge tank, then use LOTS of WD-40 on the manifolds between the carbs and the heads.

I am a motorcyclist, NOT a biker.


1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
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post #10 of 25 (permalink) Old 12-11-2011, 07:07 PM
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Kawasaki referred to the goats belly as a "Power Chamber"... so it really was not a big mystery as to what was inside, but thanks for confermation, too bad we still have no photos..

Removing the GB to take heat off the R/R sounds logical.. But as it is so much easier to simply relocate the R/R compared to removing the GB it really makes no sense...as lopping off the GB will effect power output and make the bike sound like crap.

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