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Discussion Starter #1 (Edited)
Necessity as they say, is the mother of invention. I've seen a few of these home brew carb syncs, and decided it was time i made my own. Most of the ones i saw online were for 2 cyl, but the same principals apply, just with another set of hoses. The setup is pretty simple

24' 1/8" id "fish tank" hose - $3.00
2 - tee's with valves - $1.00
4 - 1/8" barbs
2 stroke oil
zipties
old metal shelf (or scrap lumber)

I used to the two tee's with valves so that i could control how quickly the fluid moved when syncing. Looking back, i'm not really sure that I needed them, but at 50 cents a piece, it really doesn't matter. I think just having the tee installed (with the valve full open) was enough to constrict the lines. Just be cafefull and don't be an idiot like me and have one of the valves open a little too much and introduce air into the mixture.. <grrrrrrrr> hahaha

I used the barbs at the end of the fish tank tubing, and inserted them into the vacuum hoses from the carbs. I probably could have not used the barbs and attached them directly to the carbs, but that looked like a lot more work ! Assembly is pretty simple, and self explanatory and took about 10 minutes to build. Be careful when adding the oil into to hose.. I put one end of the hose into the bottle of oil, and then just sucked on the other end until i had what i thought was enough fluid. I made the mistake of doing one hose at a time, i should have done both at the same time so that i'd have the same amount of fluid in each line.. Oh well..

That's about it, good luck !

Oh yeah, and this worked like a champ !!!!

-=<> Aaron <>=-
---edit---
I forgot to mention, the location of the first to lines is higher then the second set. That's becuase i didn't have an equal amount of fluid in each pair of lines.. My mistake. With the zipties semi loose, i can move them up and down as i need.



 

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you said it worked like a champ which is sweet but were your carbs off? and if so how many miles do you have?
 

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Discussion Starter #3
you said it worked like a champ which is sweet but were your carbs off? and if so how many miles do you have?
The carbs were off yes.. Mainly between 1 & 2, 3 & 4 were a little off, but not too bad. I probably took 30 minutes or so. I didn't have a big fan handy to cool the engine off, so i tuned, and then let the motor rest for a little bit. I'm pretty sure they were off because i shimmed the needles last weekend. Could be that or from when i purchased the bike. When i first bought it, it had to immedately go to the service dept because the nuckleheads left fuel in tank/bowls and the ever popular ethanol crapped it up. I'm pretty sure they would have synced the carbs after removing and reinstalling, but who knows from the same people who don't have enough common sense to drain the bowls. Oh yeah, 3,500ish miles

-=<> Aaron <>=-
 

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i built the two bottle method for my ninja 250R ... this doesn't look any harder.. were they off a lot or just a lil ?
 

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I also use a home made set up to sync my carbs.

I use 1 length of hose, loop it and fill it with fluid. i did not bother to use two set ups becuae your only sync two carbs together at a time. Your way is easier though so you do not have to switch the lines around 3 times.

I did not bother with the Ts you used on the bottom. Works like a charm though. More accurate then mercury.

I did mine at 3000 mileson my 08 zzr. Noticed it runnin different. Throttle response wasn't the way it should be, and it ust had a drone to it. Wasn't a HUGE deal but i could feel it. They were way off. Then i shimmed my needles a few hundred miles later and it as off again. Not sure if it was because of the needles or not. Either way it as off again. I synced them again last night and i'm going to see what happens this time.
 

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The carbs were off yes.. Mainly between 1 & 2, 3 & 4 were a little off, but not too bad. I probably took 30 minutes or so. I didn't have a big fan handy to cool the engine off, so i tuned, and then let the motor rest for a little bit. I'm pretty sure they were off because i shimmed the needles last weekend. Could be that or from when i purchased the bike. When i first bought it, it had to immedately go to the service dept because the nuckleheads left fuel in tank/bowls and the ever popular ethanol crapped it up. I'm pretty sure they would have synced the carbs after removing and reinstalling, but who knows from the same people who don't have enough common sense to drain the bowls. Oh yeah, 3,500ish miles

-=<> Aaron <>=-
when you sync them do you just sync 1 with 2 and 3 with 4 or how does that work ?
 

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Each carb has a vacuum line on it. the vacuum is created by the amount of air flowing through that individual carb. In order for the engine to run perfectly, it needs the same amount of air/fuel in each cylinder.

So, the if the vacuum is the same in each carb, that means the airflow is the same. If the air flow is the same, that means the amount of fuel will be the same because the fuel is drawn into the carb by vacuum.

To simplify things. Think of it as 1 length of tube, two open ends. You create a "U" shape with the tube, and fill it part way with fluid. Similar to how a straw works... If you were to suck on one end of a straw, the fluid would come to the end you are sucking on. Instead of you sucking on the straw, The carb does the sucking for you (with the vacuum). So if you were to leave the one end open, it would suck the fluid right into the engine, just as a straw would suck up fluid into your mouth.

Now, if you were to hook both ends up to each carb, you lock the fluid in the middle because there is a vacuum on each side of the fluid. Which ever side has a greater vacuum will have a higher level of fluid. The key is to adjust between the two to create equal vacuum.

Before there is any vacuum created by the engine (tubes disconnected) the fluid levels will automatically be at the exact same height because the amount of vacuum (0) is the same on each side. If you were to use your mouth and suck on one end of the tube, it would be higher on that side. Just as if a carb were pulling the vacuum. To two carbs are fighting each other to pull the fluid. When they are pulling the same amount, the fluid levels will be equal.

The set up posted here uses to of these set ups to monitor all 4 carbs. There are two lengths of tube, shaped in a "U". Each Length is hooked up to two carbs. They are 100 percent independent of each other. Before any vacuum is applies, he lines the level of fluid up in all 4 tubes. This gives you equal levels in all 4 tubes, which is where you want to end up by adjusting the carbs.
 

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I also use a home made set up to sync my carbs.

Either way it as off again. I synced them again last night and i'm going to see what happens this time.
:popcorn

I bought 12' of tubing today and a pint of 2 stroke oil. That way if it gets sucked into the engine it will just burn off - no lasting results. I plan to do mine Wednesday. Once I am finished, I will cap each end of the setup off with golf tees and sit it in the corner for the next time I need to use it.
 

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I could not find a yardstick lying around the house (there's one here somewhere), so I put one end of the tube in the oil and used suction to draw some fluid up into the hose. Then I wiped off the end and zip tied (loosely) the tubing to a carpenter's level. One trick to get air bubbles out - spray a shot of canned air into the end with the bubbles in it. That got the 3 air bubbles I had in the line out.

Judging by the force it took to suck the oil up into the 1/8" diameter tubing I'd say the oil should be fairly stable in the tube, so no worries of it jumping around when syncing the carbs.

New air filter (K&N), iridium plugs, carb sync, needle shim and installing a 12V outlet for my GPS. I might even change the air in my tires for a few extra horsepower.














OK...that last part was a joke, in the event anyone took me seriously.
 

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Each carb has a vacuum line on it. the vacuum is created by the amount of air flowing through that individual carb. In order for the engine to run perfectly, it needs the same amount of air/fuel in each cylinder.

So, the if the vacuum is the same in each carb, that means the airflow is the same. If the air flow is the same, that means the amount of fuel will be the same because the fuel is drawn into the carb by vacuum.

To simplify things. Think of it as 1 length of tube, two open ends. You create a "U" shape with the tube, and fill it part way with fluid. Similar to how a straw works... If you were to suck on one end of a straw, the fluid would come to the end you are sucking on. Instead of you sucking on the straw, The carb does the sucking for you (with the vacuum). So if you were to leave the one end open, it would suck the fluid right into the engine, just as a straw would suck up fluid into your mouth.

Now, if you were to hook both ends up to each carb, you lock the fluid in the middle because there is a vacuum on each side of the fluid. Which ever side has a greater vacuum will have a higher level of fluid. The key is to adjust between the two to create equal vacuum.

Before there is any vacuum created by the engine (tubes disconnected) the fluid levels will automatically be at the exact same height because the amount of vacuum (0) is the same on each side. If you were to use your mouth and suck on one end of the tube, it would be higher on that side. Just as if a carb were pulling the vacuum. To two carbs are fighting each other to pull the fluid. When they are pulling the same amount, the fluid levels will be equal.

The set up posted here uses to of these set ups to monitor all 4 carbs. There are two lengths of tube, shaped in a "U". Each Length is hooked up to two carbs. They are 100 percent independent of each other. Before any vacuum is applies, he lines the level of fluid up in all 4 tubes. This gives you equal levels in all 4 tubes, which is where you want to end up by adjusting the carbs.
I've never seen anyone explain it better haha... I'll be doing this sometime soon as well
 

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my only question about the adjustment is if they are off do you....
A: increase flow to the weaker vacuum line or...
B: decrease flow the the stronger vacuum line?
 

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my only question about the adjustment is if they are off do you....
A: increase flow to the weaker vacuum line or...
B: decrease flow the the stronger vacuum line?
There are only three screws. One for carbs 1/2 and one for carbs 3/4 and one to sync the two banks (1/2 with 3/4)

That being the case I think you turn the screw on way or the other until they are coming into balance. I have read it does not take much of a turn to change the vacuum. Once you have 1 and 2 in sync, move over to 3 an 4, then use the center screw to balance between the two banks.
 

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There are only three screws. One for carbs 1/2 and one for carbs 3/4 and one to sync the two banks (1/2 with 3/4)
gotcha! with only one screw per adjustment there is only one way to go either clockwise or counter. thanks. i would like to tackle this soon but lookin at the manual i downloaded it say special pilot screw adjuster tool required....is that true?
 

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gotcha! with only one screw per adjustment there is only one way to go either clockwise or counter. thanks. i would like to tackle this soon but lookin at the manual i downloaded it say special pilot screw adjuster tool required....is that true?
I had everything off mine last night and it looked like a small screwdriver would work. Not sure why you need a special tool. Probably so they can make even more money selling specialized tools :D
 
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