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Discussion Starter #1
Hey All,
Yesterday was slow in terms of work so I decided to do some work on the bike. My goal was to marble it and also do some troubleshooting for my temp gauge. Turns out my temp gauge itself is bad so that’s now a job for another day. With the tank off it was real easy to get the marble in on the right side of the bike, popped off the side cover on the left to get leverage on the reed valve tube and got the other one in as well. Bike still pops, primarily on the LEFT side, and since my mufflers cracked, I currently have only exhaust tips on the bike the popping is starting to annoy me, especially when I’m riding through the neighborhoods. So next thing I want to try is the Air/Fuel mixture screws. I was able to get the plug out on the RIGHT side of the carb so far. I’ve done a lot of reading on the forum as to how to set it but I still have a couple questions.
1st question, Is the screw on the RIGHT side of the carb for the rear cylinder?? I ask because if it is I’ll leave the other plugged for now, no sense in messing with something else if it’s good.
2nd question, What are the consequences of turning the screw out too much? I only plan to turn it out between 2-3 turns but just want to understand what taking out too far will do so I know what to look for.
 

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I believe the left carb is for the rear, but my engine is apart so someone will have to double check.
Look carefully at the short tubes below the carbs. It should be fairly easy to see if the tube slants down towards the front or the rear on a given carb.

Going too rich will cause stumbles and mis-fires at idle and poor response coming off idle. It will hurt your cruising MPG, and may cause excessive carbon build up.
Since you're running without a muffler, that carbon may find it's way onto your rim (as it did with my bike when I had an oversize main jet).

Have you done an ear shave?
I found my bike did NOT need any tuning adjustments between mufflers/no mufflers when I had stock exhaust.
However, after an earshave, putting the mufflers back on caused a rich mis-fire when accelerating.
If you have done an earshave, I'd expect your bike to require different tunings from front to rear, since you're running one with a muffler and one without.

When I tuned my idle screws, I turned one in until the idle started to drop and noted where that was at (2 turns out).
Then I turned that same one out until the idle started to drop and noted where that was at (3.5 turns out).
That gave me my acceptable range (2 to 3.5 turns).
I then chose a spot on the lean side of the middle (2.5 turns).
Do the same with the other carb (when you are able).
Anything in the range that you find should be fine to run with.

Mine pops on decel (which I actually like). Going out 0.5 turns got rid of the popping. I can't say the MPG difference between 2.5 and 3 turns. I didn't run long at 3 turns.
 

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Discussion Starter #3
I have NOT done the ear shave, and to clarify I have no mufflers at the moment. The clamps cracked off of both of them. So they’re sitting in my basement at the moment waiting to be repaired. I have read a few times through my searches that the GB provides enough back pressure. Not sure if that’s accurate but the bike feels good (At least to me anyway). I did adjust the one screw I uncovered but still pops so maybe you’re right and it’s the other.
When you say “tubes” I’m assuming you mean where the carb mounts to the cylinders, and because that screw is closest to the rear tube is why I asked if the screws were opposite of the exhaust
 

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If the right carb tube where the carb mounts to the cylinders is towards the rear, than that's tuning the rear cylinder.
The rear cylinder does have it's exhaust on the left side of the bike.

The GB does provide some back pressure. Enough that running straight pipe after the GB doesn't require retuning.
However the ear shave reduces the intake restriction considerably. I saw a tuning difference between mufflers and no mufflers.
In your case with no earshave and both mufflers missing, your tuning should be close to stock (+/- your preferences).

Keep in mind, that the GB does connect both pipes, so a pop in the back cylinder will come out both pipes, just louder on the left side.
Same with the front, it will be out both pipes, only louder on the right.
 

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Hey All,
Yesterday was slow in terms of work so I decided to do some work on the bike. My goal was to marble it and also do some troubleshooting for my temp gauge. Turns out my temp gauge itself is bad so that’s now a job for another day. With the tank off it was real easy to get the marble in on the right side of the bike, popped off the side cover on the left to get leverage on the reed valve tube and got the other one in as well. Bike still pops, primarily on the LEFT side, and since my mufflers cracked, I currently have only exhaust tips on the bike the popping is starting to annoy me, especially when I’m riding through the neighborhoods. So next thing I want to try is the Air/Fuel mixture screws. I was able to get the plug out on the RIGHT side of the carb so far. I’ve done a lot of reading on the forum as to how to set it but I still have a couple questions.
1st question, Is the screw on the RIGHT side of the carb for the rear cylinder?? I ask because if it is I’ll leave the other plugged for now, no sense in messing with something else if it’s good.
2nd question, What are the consequences of turning the screw out too much? I only plan to turn it out between 2-3 turns but just want to understand what taking out too far will do so I know what to look for.
The right side carb is for the rear cylinder.

Turning the air mixture screw to the left, looser, will richen the idle mix, which should help reduce popping.

This idle mixture adjustment won't affect running over ... about 2000 rpm.

Have you been through the carbs? Stuck coast enrichers will cause popping also, and straight exhaust usually has the tendency to pop.
 

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Discussion Starter #6
I took the other lead plug out, I’m going to take the bike out and mess with the tuning to see if I can get it to at least pop less. I don’t mind a few pops here and there but when it sounds like a gun fight it needs to be looked at. If I can’t reduce it then I guess I’ll start hunting down a possible exhaust leak. The only other thing I can think of is if it’s at all possible the marbles didn’t completely seal up the hose. It felt snug but that would be my luck lol
 

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Could stick a bolt in the hose and put a clamp on it, but I don't think that's the problem causing the pops.
 

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Discussion Starter #8
Hey All,
Yesterday was slow in terms of work so I decided to do some work on the bike. My goal was to marble it and also do some troubleshooting for my temp gauge. Turns out my temp gauge itself is bad so that’s now a job for another day. With the tank off it was real easy to get the marble in on the right side of the bike, popped off the side cover on the left to get leverage on the reed valve tube and got the other one in as well. Bike still pops, primarily on the LEFT side, and since my mufflers cracked, I currently have only exhaust tips on the bike the popping is starting to annoy me, especially when I’m riding through the neighborhoods. So next thing I want to try is the Air/Fuel mixture screws. I was able to get the plug out on the RIGHT side of the carb so far. I’ve done a lot of reading on the forum as to how to set it but I still have a couple questions.
1st question, Is the screw on the RIGHT side of the carb for the rear cylinder?? I ask because if it is I’ll leave the other plugged for now, no sense in messing with something else if it’s good.
2nd question, What are the consequences of turning the screw out too much? I only plan to turn it out between 2-3 turns but just want to understand what taking out too far will do so I know what to look for.
The right side carb is for the rear cylinder.

Turning the air mixture screw to the left, looser, will richen the idle mix, which should help reduce popping.

This idle mixture adjustment won't affect running over ... about 2000 rpm.

Have you been through the carbs? Stuck coast enrichers will cause popping also, and straight exhaust usually has the tendency to pop.
I have not been through them, I don’t have a lot of experience with carbs. I’m learning slowly from this forum but not quite there yet. What normally causes that to stick? Gunk? Or is that a sign of wear?
One more question on those A/F screws, most of what I read says “turn them all the way in first but be sure not to force them”. What is all the way in? Is it when you first start to feel the spring tension push back? That’s what I did and I want to be sure I’m doing it right.
 

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All the way in is where it bottoms out in the hole, with light finger pressure. If you torque it tight, you can bend the tip, which is like the tip of a dart. Then good luck finding one.

Shellac, gunk, sticky corn goo ... Can stick the 'piston'. Or the rubber in the diaphragm can crack, rot, or rear.
 

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Discussion Starter #10
https://www.partzilla.com/catalog/kawasaki/motorcycle/2005/vulcan-750-vn750-a21/carburetor-parts

Are the A/F screws called "SCREW-PILOT AIR 16014-1054" ? if so they're $19 for the screw alone, not to mention the springs etc. I'd rather just be gentle and do it the right way and go at it with a light touch lol.

But back to what you were saying earlier, should i double my sea foam use?. I heard of guys spraying it right into the carbs, where do you do that? do you remove the fuel line coming from the petcock? I took the tank off for the first time the other day and finally got a good look at the tubes so I have a little better idea of what goes where.
 

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No, just use the prescribed amount of Seafoam. It's either 1 or 1.5oz per gallon of gas, in the tank. Sometimes it can be added straight to the carb through the fuel line, but that just cleans the bowl.

The coast enrichers are easily accessible if you want to peek inside. It's the circular cover facing out as you look at the side of the carb. Three screws I think.
 

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Discussion Starter #12
No, just use the prescribed amount of Seafoam. It's either 1 or 1.5oz per gallon of gas, in the tank. Sometimes it can be added straight to the carb through the fuel line, but that just cleans the bowl.

The coast enrichers are easily accessible if you want to peek inside. It's the circular cover facing out as you look at the side of the carb. Three screws I think.
Is this what you’re referring to? If I take a peek how many tiny pieces pop out?
 

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Is this what you’re referring to? If I take a peek how many tiny pieces pop out?
That's it. Check the manual but I think it's just the diaphragm with piston attached, and a spring.
 

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Discussion Starter #14
Ok cool thanks, I found it, doesn't look too daunting. assuming it should be clean and gunk free in there.
It’s part “7” description is lower on the page
 

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Ok cool thanks, I found it, doesn't look too daunting. assuming it should be clean and gunk free in there.
It’s part “7” description is lower on the page
If you're in there, could give the passages a shot of carb cleaner.

Is this the bike that's missing one muffler? Could cause some popping.
 

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Discussion Starter #16
If you're in there, could give the passages a shot of carb cleaner.

Is this the bike that's missing one muffler? Could cause some popping.
I only have SeaFoam and Sta-bil at the moment but not the spray bottle, would need to get some carb cleaner, as far as mufflers, I have none on the bike, i still have them though, just wondering what's the consensus on JB-Weld being able to hold the clamps on the mufflers?? will the heat just break them again?

You can see it here, and if you look close enough you can see that this is a "Lulcan 750" , my "V" cracked on the side cover lol :grin2:
 

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Discussion Starter #17
So I was reading previous posts on this and found this from Ubertalldude:

“Vacuum caps on the exhaust inlets is fine, so long as they seal tightly. They are effectively the same as coasters, but look a little different (I think they look cooler on a black engine)
The popping doesn't damage anything, but it's less than ideal as it puts extra stress and heat on the exhaust (which it can handle fine, albeit with the side effect of bluing) Did you also cap off the vacuum port on the right-side carb? That could lean you out and cause excessive popping.
As for reducing the popping, just adjust your right-side carb's idle air mix screw out (CCW) 1/4-1/2 turn at a time to see if it helps with the popping. Should work fine so long as your carbs are clean and in good working order.”

I did NOT plug the vacuum port on the right carb, where is that??

Here’s a short vid of how the bike sounds. Of course yesterday the popping wasn’t terrible but it’s still there. The vid is real shaky, but it caught the audio well.

https://youtu.be/mhnwhtWUYZU
 

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So I was reading previous posts on this and found this from Ubertalldude:

“Vacuum caps on the exhaust inlets is fine, so long as they seal tightly. They are effectively the same as coasters, but look a little different (I think they look cooler on a black engine)
The popping doesn't damage anything, but it's less than ideal as it puts extra stress and heat on the exhaust (which it can handle fine, albeit with the side effect of bluing) Did you also cap off the vacuum port on the right-side carb? That could lean you out and cause excessive popping.
As for reducing the popping, just adjust your right-side carb's idle air mix screw out (CCW) 1/4-1/2 turn at a time to see if it helps with the popping. Should work fine so long as your carbs are clean and in good working order.”

I did NOT plug the vacuum port on the right carb, where is that??

Here’s a short vid of how the bike sounds. Of course yesterday the popping wasn’t terrible but it’s still there. The vid is real shaky, but it caught the audio well.

https://youtu.be/mhnwhtWUYZU
Ok, tell me again, what's your exhaust setup?

The vac port on the right carb is on the side of the carb facing straight out. Had the vac hose for the suction valve on it.

As a little hooligan trick, at the top of the mountain I reach down and pull the cap off the right side vac port, then do a long decel down the mountain. It goes off like a cannon. I don't do it anymore, since I don't want to buy new mufflers.

Open exhaust, lean air adjustment, and a vacuum leak can all contribute to popping.
 

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Discussion Starter #19
I have stock intake and no mufflers, I'm using 6 inch exhaust tips

Here is a pic of the right side of the carb, is that single line clamped on a vacuum line? I didn't touch that line when I pulled the tank off last week. I just disconnected the lines right off the petcock, this way I had them just sitting there lined up in order they needed to be reconnected.

If that's it, what do you guys use to plug it?
 

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I have stock intake and no mufflers, I'm using 6 inch exhaust tips

Here is a pic of the right side of the carb, is that single line clamped on a vacuum line? I didn't touch that line when I pulled the tank off last week. I just disconnected the lines right off the petcock, this way I had them just sitting there lined up in order they needed to be reconnected.

If that's it, what do you guys use to plug it?
Yes that's it.

You can cut a short piece of that hose, stick a bolt in one end, then put it on the carb.

Or find a vacuum cap.

Are you coastered? If so, the other end of the hose may be open if you removed the suction valve. Open vac port will make it pop, sometimes like a cannon.

Those pipes may always pop. But get the vac leak stopped, then try a richer air adjustment, if you're still wanting to reduce popping.
 
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