Restriction of Stock Exhaust With Ear Shave - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
Engine / Exhaust / Cooling
\ From the radiator, through the case and out
the exhaust. If it has to do with the cooling,
engine or exhaust, discuss it here!

 2Likes
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 11 (permalink) Old 05-03-2019, 11:22 AM Thread Starter
Senior Member
 
Jason Pittenger's Avatar
 
Join Date: Apr 2018
Location: Northern Illinois (Not Chicago)
Posts: 231
iTrader: (0)
 
Garage
Restriction of Stock Exhaust With Ear Shave

I intend this to be informative to people wondering about how removing the stock mufflers affect flow/tuning while keeping the Goats Belly. As I've read through this forum, I've had a hard time finding information on how the bike runs in my exact setup. Namely, an Ear Shave with the Goats Belly, and straight pipes after the GB. Many have the Ear Shave with stock exhaust, or Ear Shave with aftermarket exhaust, or stock intake and aftermarket exhaust. Not many appear to have done my particular arrangement.

Last night, in preparation to pull my carbs (again), I started and idled my bike to drain all the gas out. Since the only goal was to drain the carbs, I slid my mufflers back on to the GB to keep noise to a minimum. With my ear shave, 38/138 jets, 1 shim and 4 turns on the screws, this made it rich to the point of not needing the choke when cold. It also make the exhaust gas visibly black as it warmed up. I was amazed how much restriction it added at idle!

Removing the mufflers did not have this drastic of effect before the ear shave. Previously, pulling the mufflers had little to no change on the richness or idle speed.

Therefore, I would conclude:
1. The stock mufflers do not seem to have much restriction when used with the stock air intake.
Or more specifically, the stock intake is much more restrictive than the stock exhaust is.
Therefore, only removing the mufflers results in no needed changes to the tuning.

2. Doing an ear shave with the stock mufflers seems to lean out the mix a bit, but not a lot.
This seems to be the experience with people on the forum running 38 pilots with 132-138 mains with an ear shave and stock exhaust.

3. After an ear shave is complete, the mufflers become the most restrictive portion of the bike.
The combination is greater than the sum of the parts!
This seems to be the experience with people on the forum running 40-42 pilots with 140-142 mains with an ear shave and aftermarket exhaust.

4. The Goats Belly does not seem to have much restriction, and running straight piped after it is comparable to a full aftermarket exhaust.

Once I have my jets tuned in, I'll post back with my results.


'89 Vulcan 750 Bought 4/12/18 @ 17805.9 miles $800
Purchased stock. Wrecked once
22490.0+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB
110/90 Front Tire
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages
Ear Shave (wo/ coasters) 40/140 NO shims 45MPG
MCCT conversion

Planned modifications:
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance
Jason Pittenger is offline  
Sponsored Links
Advertisement
 
post #2 of 11 (permalink) Old 05-03-2019, 12:51 PM
Super Moderator
 
Join Date: Feb 2013
Location: SW Florida
Posts: 2,442
iTrader: (5)
 
ear shave and stock exhaust in my case didnt need any change of jets, just adjusting the air bleed (idle mixture screw). which tells me that mine was properly jetted from the factory.

2005 VN750

Sold 11-27-17
michiganteddybear is offline  
post #3 of 11 (permalink) Old 05-03-2019, 07:37 PM
Junior Member
 
warbike's Avatar
 
Join Date: Sep 2011
Posts: 18
iTrader: (0)
 
I have the same setup on my Vn700, ear shave, goats belly and the the stock mufflers but baffles removed so basically straight piped after the GB. Only just recently got it running and I don't know what jets are in the carb so I don't have any experience with how it runs yet. I'll be interested to see what you end up doing with the carbs.

Sent from my moto z3 using Tapatalk
warbike is online now  
 
post #4 of 11 (permalink) Old 05-03-2019, 08:59 PM
Super Moderator
 
Join Date: Feb 2013
Location: SW Florida
Posts: 2,442
iTrader: (5)
 
the thing to remember is EVERY situation is different. while mine was fine with stock jetting (I am at sea level), others with slightly different altitudes may need different jetting.

basically, just because it works for one person, does NOT mean it will work for you!

2005 VN750

Sold 11-27-17
michiganteddybear is offline  
post #5 of 11 (permalink) Old 05-03-2019, 09:05 PM
Junior Member
 
warbike's Avatar
 
Join Date: Sep 2011
Posts: 18
iTrader: (0)
 
True, I don't know where Jason is located but if he let's me know at least above sea level attitude, I'll be able to adjust based on my +4000 ft level and fine tune from there.

Sent from my moto z3 using Tapatalk
warbike is online now  
post #6 of 11 (permalink) Old 05-04-2019, 07:20 AM
GDI
Senior Member
 
Join Date: Aug 2017
Location: Madison, WI
Posts: 170
iTrader: (0)
 
Jason is down in Northern Illinois, so probably 750ft (just guessing).

GDI
GDI is online now  
post #7 of 11 (permalink) Old 05-04-2019, 12:27 PM
Old Fart
 
Knifemaker's Avatar
 
Join Date: Jun 2004
Location: Catawissa, MO
Posts: 11,603
iTrader: (4)
     
Garage
You should also keep in mind that a less "restrictive" exhaust is not necessarily a good thing. The goats belly is referred to by Kawasaki as the "tuning chamber"... balancing out the exhaust pulses from both cylinders and providing the needed back pressure to provide the best compromise over the entire rpm range.
Straight pipes work fine for WFO operation, but not at speeds right off idle.
As much as the bike does love being opened up, many owners seem to prefer riding at lower rpms (this is one of the attributes of a "cruiser")

I also must mention that those with open pipes who claim gains in horsepower have not offered dyno data to support this, and seem to miss the idea that switching to simple straight pipes just removes a lot of weight from the bike, the entire stock system is freaking heavy.
roadpouring likes this.

If You Are Not Sure If I Am Joking or Not....I AM !!Photos:
http://www.flickr.com/photos/knifemaker1954/sets/
Knifemaker is offline  
post #8 of 11 (permalink) Old 05-04-2019, 09:40 PM Thread Starter
Senior Member
 
Jason Pittenger's Avatar
 
Join Date: Apr 2018
Location: Northern Illinois (Not Chicago)
Posts: 231
iTrader: (0)
 
Garage
Quote:
Originally Posted by Knifemaker View Post
You should also keep in mind that a less "restrictive" exhaust is not necessarily a good thing. The goats belly is referred to by Kawasaki as the "tuning chamber"... balancing out the exhaust pulses from both cylinders and providing the needed back pressure to provide the best compromise over the entire rpm range.
Straight pipes work fine for WFO operation, but not at speeds right off idle.
As much as the bike does love being opened up, many owners seem to prefer riding at lower rpms (this is one of the attributes of a "cruiser")

I also must mention that those with open pipes who claim gains in horsepower have not offered dyno data to support this, and seem to miss the idea that switching to simple straight pipes just removes a lot of weight from the bike, the entire stock system is freaking heavy. [IMG class=inlineimg]/forum/images/smilies/icon_wink.gif[/IMG]
This is why I left my GB on. (That, and I am too cheap/lazy to replace it 😉 ). I can't claim more HP or anything. I only observed that the stock intake is more restrict than the stock mufflers, and after an ear shave, the mufflers are restrictive enough to change the tuning. However, the mufflers are not restrictive enough on their own that removing them requires tuning changes.

I rode it today (briefly) with the mufflers back on, and it stumbled and bucked at WOT.

As a side note, I don't care for the ear shave intake noise with stock exhaust. I never heard it before, because I always had the mufflers off.


'89 Vulcan 750 Bought 4/12/18 @ 17805.9 miles $800
Purchased stock. Wrecked once
22490.0+ miles

Completed modifications:
Removed mufflers, straight pipes out of GB
110/90 Front Tire
Pick-up coil re-gapped to .020"
Compufire 55402 r/r series regulator
USB Outlet + Voltmeter
Repainted Metallic Blue w/ new tank bages
Ear Shave (wo/ coasters) 40/140 NO shims 45MPG
MCCT conversion

Planned modifications:
Custom LED turn signals
Windshield
Highway Pegs
(Possible) ignition advance
Jason Pittenger is offline  
post #9 of 11 (permalink) Old 05-05-2019, 08:06 AM
Senior Member
 
Spockster's Avatar
 
Join Date: Nov 2012
Location: WV
Posts: 6,490
iTrader: (5)
   
Fired mine up with the mufflers removed, it hesitated bad off-idle.

2003-21k mi
Shaved w/UniPK92+Stock Jets-TPE/MOSFET-Shinko Tires-AGM batt-bags-chrome-LEDs...more
__________________________________________________ ____________
Repair Manual: http://www.mediafire.com/file/mj7z81..._Catalogue.pdf

Owner's Manual: http://www.mediafire.com/file/nscb5f...ers+Manual.pdf
Spockster is offline  
post #10 of 11 (permalink) Old 05-06-2019, 05:52 AM
Members who have donated towards server costs
 
Join Date: Nov 2007
Location: Chandler, Arizona
Posts: 2,848
iTrader: (0)
 
I can guarantee that a completely stock bike with the pilot screws turned out a little will be faster and make more power than a bike with modified intake/exhaust. More noise almost always equals less power. Running what amounts to an open intake and open pipes puts it beyond the tuning range of the carbs (one of the only advantages of EFI) An open intake and pipes is great for full throttle. That's why I run my drag race car with a K&N screen and open headers. It also has a tunnel ram manifold, and ported and polished heads, and a high lift long duration cam with a short ramp speed. All of that has one purpose. To get as much power out of it at high RPM. And since it has a carb, it does not run well at all at lower rpm, though putting a restrictive filter and a set of Flowmasters makes it drivable on the street, once you get the hang of it. I do not race my motorcycle, and would not want it to run that way. I want good low end torque and decent midrange. I don't ride it at full throttle. I always used the Vulcan 750 as a touring bike.

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
VN750Rider/Jerry is offline  
Sponsored Links
Advertisement
 
Reply

Bookmarks

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

Once registered, your User Name"cannot be changed". We can make exceptions within 7 days, but after that, it is set in stone.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome