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Discussion Starter #1 (Edited)
I've been talking with several of the local wrenches about the carbs, shave, vac lines, and goat. Here's some items I picked up from them:

  • when removing the goat, replace it with a x-over tube.
  • when removing the vacuum valve/tubes if needed couple vac lines together if needed to maintain vac hose balance.
  • It's more difficult to maintain carb sync if CV carbs don't share the same air box. The shave with filter pods is more cosmetic than functional.
I shaved - for looks - but reinstalled my drilled goat after R/R relocate.
 

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Old Truck Junkie
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I've been talking with several of the local wrenches about the carbs, shave, vac lines, and goat. Here's some items I picked up from them:

  • when removing the goat, replace it with a x-over tube.
  • when removing the vacuum valve/tubes if needed couple vac lines together if needed to maintain vac hose balance.
  • It's more difficult to maintain carb sync if CV carbs don't share the same air box. The shave with filter pods is more cosmetic than functional.
I shaved - for looks - but reinstalled my drilled goat after R/R relocate.
I tried to use the car air filters on mine but they for some reason did not flow enough air. I do not feel that the pods are as good a filter, but the bike runs a whole lot better with them than the others. And it looks a whole lot better with the pods.
 

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"when removing the goat, replace it with a x-over tube."

TRUE. The "belly" is as Kaw calls it a "power chamber". It provides better low end grunt. Think of the system a being like a 2 into 1 setup. It just happens to be more of a 2 into 1 into 2 again thing...

"when removing the vacuum valve/tubes if needed couple vac lines together if needed to maintain vac hose balance."

TRUE. Well, for the most part. The vacuum lines off the carb going to the right airbox are already joined. Any time you connect them they should meet at a shared chamber of some kind.


"It's more difficult to maintain carb sync if CV carbs don't share the same air box. The shave with filter pods is more cosmetic than functional."

Kinda True. The carbs need to have the same "restrictions", but generaly filters like the K+N pods are so unrestrictive that you'd have to be feeding a mighty big engine to over come their limits. This was mostly a problem with old inline fours that had 4 pods across . The outer pods tended to collect dirt faster , to the point that if not cleaned on a periodic bassis they would effect the balance.
And the fact that CV carbs are more dependent on engine vacuum, (engine side of the carb) for metering purposes, air restriction would have to be highly diffrent.

KM
 

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Discussion Starter #4
Good post KM.

One of the people I spoke with on this thread was a crotch rocket builder. His favorites were the FZ Yamaha's with the Pop's Yoshi kits - 4 cyl with 4 into 1. The instructions for the kit was to leave the stock air box in place but drill several 1/2 to 3/4 inch holes in the rear of the box and use a high flo air filter.

I thought this practice was 'old news' until my brother had his Triumph (900 triple) serviced at the dealer. They asked him if he wanted a performance boost free of charge for being a Triumph owner - and they did the same thing: drilled the air box and tuned the carbs. Now I can't keep up with him - it made a big difference on his bike.

What I wonder about when using pods is a vacuum effect that might change our carbs performance. When air is passing by our shaved intakes, is there a vacuum created by the passing wind that effects the tuning and balance vs. the stock air box? The pressure difference at the carb's intake pointing 180 degrees would be different depending on how fast the bike is going.

Just thinking out loud...
 

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What I wonder about when using pods is a vacuum effect that might change our carbs performance. When air is passing by our shaved intakes, is there a vacuum created by the passing wind that effects the tuning and balance vs. the stock air box? The pressure difference at the carb's intake pointing 180 degrees would be different depending on how fast the bike is going.

Just thinking out loud...
Theoretically, yes. The air box is there to provide a still source of air for the carbs. Once it's moving, you've lowered the external air pressure (inversely proportional to speed), and that should affect tuning.

I'm still trying to think about the holes in the airbox and how that boosts performance...(theoretically). Anyone?
 

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Old Truck Junkie
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The only problem that I noticed when doing the ear shave was with the carb vent hose that was pluged to the right ear. Now when riding in strong wind the air tends to go into that hose and push the carb diaphram enough that it tends to slow the bike down and then it speeds up when past the gust of wind. It is not the push on the shield that I refur to.

With the holes in the air box, would one get unfiltered air into the carbs and engine??
 

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The only problem that I noticed when doing the ear shave was with the carb vent hose that was pluged to the right ear. Now when riding in strong wind the air tends to go into that hose and push the carb diaphram enough that it tends to slow the bike down and then it speeds up when past the gust of wind. It is not the push on the shield that I refur to.

With the holes in the air box, would one get unfiltered air into the carbs and engine??
Find you a small in line fuel filter for 1/4 inch fuel line. Most likely in a lawnmower shop or even at Wal Mart. Plug it in the line and hang it high next to the frame under the tank.
Also the holes in the air box have to be before the filter so you don't get unfiltered air in the engine. This allows more air to the filters.
Don't forget when you marble and shave the ears you can use the right side hose from the reed valve to raise the crankcase vent to just below the frame under the tank.
 

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What I wonder about when using pods is a vacuum effect that might change our carbs performance. When air is passing by our shaved intakes, is there a vacuum created by the passing wind that effects the tuning and balance vs. the stock air box? The pressure difference at the carb's intake pointing 180 degrees would be different depending on how fast the bike is going.
Just thinking out loud...

They could, but I doubt they do. The "pod" filters don't really stick out into the airstream like the stock ears. And they pull air in from a 360 degree area around the filter. Both K+N's and Uni filters do this and although differ in design, are about the same size.
The vacuum line that goes into the right stock air box is critical. The post about using a filter and tucking it up under the gas tank is 100 % right-on, as any change in air pressure around this line will effect the carbs performance.

KM
 

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Find you a small in line fuel filter for 1/4 inch fuel line. Most likely in a lawnmower shop or even at Wal Mart. Plug it in the line and hang it high next to the frame under the tank.
Also the holes in the air box have to be before the filter so you don't get unfiltered air in the engine. This allows more air to the filters.
Don't forget when you marble and shave the ears you can use the right side hose from the reed valve to raise the crankcase vent to just below the frame under the tank.
I have the small filter, but I probably don't have it up hidden enough from the air flow.

I still don't understand where they drill the holes in the air box. All the air in the box is filterd air, any hole in the box will cause unfiltered air to go in the engine. The only place that I see that holes can be drilled is at the air intake of the ears around the square intake hole.
 

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You may be confusing the drilled airbox for the Triumph with doing it on the Vulcan.
On bikes that have the exhuast pipes coming from the front of the bike (ie: Triumphs, Nighthawks) the carbs are usually facing towards the back. The air intake is typically a box with a filter in it that sits under the front of the seat and back of the tank. Pretty restrictive air intake since all the air is coming in through a single hole in one side of the box. By drilling holes in the box you are allowing more air to flow to the carbs. The air still passes through the filter before going to the carbs.
 

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You may be confusing the drilled airbox for the Triumph with doing it on the Vulcan.
On bikes that have the exhuast pipes coming from the front of the bike (ie: Triumphs, Nighthawks) the carbs are usually facing towards the back. The air intake is typically a box with a filter in it that sits under the front of the seat and back of the tank. Pretty restrictive air intake since all the air is coming in through a single hole in one side of the box. By drilling holes in the box you are allowing more air to flow to the carbs. The air still passes through the filter before going to the carbs.

I get it now. They are drilling holes on the cover of the air filter ahead of the filter. Allowing more air to access the filter.
 

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So - is there an aftermarket company that makes the x-over tube that should be used when removing the GB? I ordered a kit (found it on this board) that just has straight connectors since the GB was already removed when I bought the bike. The bike has plenty of umph in most of hte range. THe only drop I noticed is around 4k - 5k there seems to be a bit of a flat spot in acceleration. Very minor but still noticeable.
 

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I did a degoat without the H pipe and have noticed no lack of power, I also drilled the muffler which reduced the backpressure.
I have goten many compliments on how it sounds, some even by HD owners, Makes me smile:).
By drilling out the screen in teh mufler it allow free flow through the muffler.
Here is a pict of what I did.


Here is a pict of a muffler when I just started.


This is looking into the muffler from teh motor side, if you do not have it off you will have a hard time seeing the screen.
 

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They could, but I doubt they do. The "pod" filters don't really stick out into the airstream like the stock ears. And they pull air in from a 360 degree area around the filter. Both K+N's and Uni filters do this and although differ in design, are about the same size.
The vacuum line that goes into the right stock air box is critical. The post about using a filter and tucking it up under the gas tank is 100 % right-on, as any change in air pressure around this line will effect the carbs performance.

KM
Agreed. (Hi, Eric!) The line going to the right ear isn't vacuum, tho; that's the vent from the float bowls. It is, however, as you say, critical. Mine's tiewrapped under the neck tube behind the thermostat housing.

Jim

J.D.
Channelview, TX
'95 Vulcan 750 "Therapy II",
aka "Raggedy Ann"
'95 VN750 project bike
'87 VN750 restoration
'93 VN1500A custom project
'97 GL1500SE Starrship "Midnite"
VROC #16185
GCVROC #33
 
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