A moment for clarification please

[Guest]

In the above figure and description from the Mikuni Carburetor Operation and Theory from http://www.iwt.com.au/mikunicarb.htm It says an interesting thing about the front and rear of the carbs... Please help me.. Is the front of the carb it is referring to the air intake side...or front of the bike... because on the CV carbs on my bike the air screw is on the back of the carb as it sits on the bike but on the air intake side of the carb...

Thank you for your assistance.

 

[Burque73]

Your carb has that screw on the front side, just like mine. The intake side, or back, has a larger opening.

 

[Burque73]

Seems counterintuitive doesn't it? The airflow goes from back to front.

 

[Guest]

Seems counterintuitive doesn't it? The airflow goes from back to front.

That's what I always understood... but lately I've actually been reading directions and manuals.... so I wanted to make sure I wasn't leaning when I was trying to richen and vice a versa....

 

[Steve]

Counterintuitive or not, all directions on the bike are made as if you are sitting on the bike, ready to ride.

The "left" side is under your left (clutch) hand. The "right" side is under your right (throttle) hand.

Yep, "front" and "back" do the same thing.

If your carbs are clean and all your o-rings are in good shape, start by lightly bottoming the pilot (mixture) screws, then back them out three full, 360? turns. That will likely be a bit too rich, but it will start easily so you can warm up the engine. Continue by turning one screw in until you hear the engine slow down just a bit, then back it out 1/4 turn. Continue with the rest of the screws. When you have done them all, go back, turn one in slowly until you hear the engine slow down, then back it out just 1/8 turn. Continue with the rest of them. It should be pretty close now. Note that they might not all be the same number of turns out now.

One other note, that picture in the link is not for your CV-type carbs.

I used to be conused by directions like that: "if it's toward the back, turning it out leans it, if it's toward the front, turning it out richens it ..." etc. It's a simple mechanical fact that turning an adjustment screw out will increase the flow of whatever it's controlling. Then, you only need to know what it's controlling. In your case, you have a fixed-size air jet and a fixed-size fuel jet that mix the fuel into the pilot mixture. Your screws control how much of that mixture is admitted into the air stream at idle and low-throttle settings.

.

 

[Killer2600]

Yes, the front of the carb is the intake side.

 

[Rich82GS750TZ]

Yes, the front of the carb is the intake side.

if that's the take-away from the first 5 posts of this thread, then I am really confused.

 

[Killer2600]

if that's the take-away from the first 5 posts of this thread, then I am really confused.

I'm sorry...the carbs are installed facing backwards so the front faces the rear and vice versa. Hope that unconfuses everything.

 

[Steve]

Not really. They are not facing backward. The carb's intake is on the rear.

The front of the carb faces the back of the cylinder head.

.

 

[Sandy]

Not really. They are not facing backward. The carb's intake is on the rear.

The front of the carb faces the back of the cylinder head.

.

I can see where people get confused on this issue. To me if a carb is in your hand or on the workbench the inlet side is generally referred to the front and the exit side is referred to as the rear. What the carb is going to be installed on at this point is irrelevant. On GSs the carbs are mounted with the inlet, or front, facing the rear of the bike. On my old FZ750 the inlet, or front, of the carb was actually facing up (downdraft configuration). It wasn't referred to as the top of the carb in that configuration. But yes, for absolute correct terminology we should use the terms inlet or outlet, but we don't always do that.

 

[Killer2600]

Not really. They are not facing backward. The carb's intake is on the rear.

The front of the carb faces the back of the cylinder head.

.

You have documentation that supports this? Not everything is in reference to position of the bike, if it was good luck with finding the front of a battery without it being in the bike.

 

[Killer2600]

I can see where people get confused on this issue. .... But yes, for absolute correct terminology we should use the terms inlet or outlet, but we don't always do that.

If you hang around the ICE (internal combustion engine) scene long enough you learn there are no absolutes with terminology. Things are referenced differently in different locals and context. One such difference nearly everyone is familiar with is trunk and boot. They refer to the same thing but the uncommon term sounds wrong to the individuals that are accustomed to what they consider the "correct" term (i.e. in america, a boot is something to put on your foot).

You could use inlet and outlet, but you would have to know which is which (i.e. how the carb works) first. So still prior knowledge is required. Another confuser would be wheels, what side is the front and what side is the back? if we refer to bike position? if we refer to position but on an automobile that has 4 wheels?

 

[Sandy]

If you hang around the ICE (internal combustion engine) scene long enough you learn there are no absolutes with terminology. Things are referenced differently in different locals and context. One such difference nearly everyone is familiar with is trunk and boot. They refer to the same thing but the uncommon term sounds wrong to the individuals that are accustomed to what they consider the "correct" term (i.e. in america, a boot is something to put on your foot).

You could use inlet and outlet, but you would have to know which is which (i.e. how the carb works) first. So still prior knowledge is required. Another confuser would be wheels, what side is the front and what side is the back? if we refer to bike position? if we refer to position but on an automobile that has 4 wheels?

LMAO. Well we all know the side can't be front or the rear ...don't we??? Who's on first?

 

[Killer2600]

LMAO. Well we all know the side can't be front or the rear ...don't we??? Who's on first?

Can a circle have sides???? :wink-new:

 

[Sandy]

Can a circle have sides???? :wink-new:

Frontside or backside?

 

[Guest]

Ok... this should confuse the issue even more.. but it may help me diagnose what I need to do.
History:
I knew nothing about carbs. 30 mpg
I tore carbs apart the first time and replaced all o rings and kinda cleaned the carb: Put it back together and things worked a bit better but still got crappy mileage.
Ran it for a couple of years. 30 mpg
Tore the carbs apart and cleaned the according to the BassCliff web page To the LETTER... (except didn't check the jet sizes ...just cleaned them). Put them back together new o rings (again)
No change... still 30 mpg.
Tore the carbs apart again cleaned jets replaced air screws put replaced all jets with stock jets (mikuni factory marks) except needle jets and slide needles. Used PO's Dynojet needles set at leanest (top slot) notch. Factory nylon washer.
Compression tests #1, 130. #2, 125. #3, 128, #4, 130. ( I know low but serviceable)
air screws lightly bottomed motor idles smooth (no throttle) ... spark plugs #1 & 2 wet #3 & #4 carbon fouled. after 1 minute of idle...

I'll wait ...but MY guess is needle jets valve and needles are leaking (Emulsion tube and slides) and need to be replaced (only things that have not been replaced)

 

[Guest]

Can a circle have sides???? :wink-new:

yep, Inside and outside......

 

[Sandy]

yep, Inside and outside......

Even if it's drawn on a piece of paper and sitting flat on the table?

 

[Killer2600]

Are you running factory intake and exhaust? If so I'd recommend setting the carbs to all factory settings (jet/needle sizes and all) and tune from there.

 

[Guest]

Even if it's drawn on a piece of paper and sitting flat on the table?

especially in 2 dimensions... lol