[Robb235]

For those of us that are too cheap to buy a carb sync tool and don't have the option to borrow or rent one, here is how to make one.

Materials you will need:

- A large wooden board. Mine was 4' tall and 1' wide.
- 24' of hose that is either 3/16" or 0.17" inner diameter. My hose's outer diamter was 1/4"
- Yardstick (optional)
- 4 1/8" hose menders. These will hook your carb sync tool to the bike.
- 2 T-fittings to connect your hoses. My t-fittings were quick disconnects for use with hoses that had an outer diameter of 1/4"
- Something to secure your hose to the board.


Overall materials

1/8" hose menders

T-fittings

0.17" ID hose

Now that you've got your materials, cut your hose into 4 equal pieces of 6' each. You will also need a 3" piece of hose to connect your two t-fittings together. Route the hoses as shown in the picture below:

Place the hose menders on the tips of your center hoses. Don't put any on the end hoses yet because we still need to put oil in your carb sync tool:

I used two stroke engine oil in my carb sync tool, that way if something should happen and the engine sucks it up it won't do any harm. It also gives it a cool green color. Automatic transmission fluid will work to and gives it a nice red color.

Now, to put oil in the carb sync tool, put one of the end hoses into your container of oil. Put the other end hose in your mouth. Block off the center two hoses (the ones that have the hose menders on them) with your thumbs. Now suck on the hose that's in your mouth and you should draw oil into your hose. After you've got enough oil in there, stand your carb sync tool upright so that all the oil flows to the bottom and evens out, as well as letting any air pockets rise to the top.

Go ahead and put the hose menders into the end hoses.

Your carb sync tool should look something like this:

Here's what my carb sync tool looked like after I adjusted the throttle bodies. My carb sync tool was extremely sensitive and this was the closest I could get them together:

 

[iatealitlebabie]

Looks good. Might have to give this one a try. :thumbup

 

[mk3turb]

Not bad! I think the first and last one were way off because of how the hoses are at the bottom, how they round. Good job though!

 

[Eric Baker]

I did pretty much the same thing like a month ago. Was gonna make a how-to but never got around to it. It worked pretty good.

Pics. First one is with water and dye, fucking got sucked into engine but luckily nothing broke. Second one is with Honda fork oil, which is higher viscocity so harder to get sucked up and less sensative, which is a big plus.

edit - sorry for the blurry pic

 

[minig0d]

hmmm I think I'll spend the extra $95 over what you did just for "storage purposes"... my carbtune 2 is 1/30th the size of that beast lol but hey if you wanna be cheap go for it!

Maybe someone else can chime in but I'm not feeling those connectors at the bottom either.... look like they'd throw off the reading a little bit Eric Baker's looks like it would look a little more accurate in that regard...

 

[Robb235]

hmmm I think I'll spend the extra $95 over what you did just for "storage purposes"... my carbtune 2 is 1/30th the size of that beast lol but hey if you wanna be cheap go for it!

Maybe someone else can chime in but I'm not feeling those connectors at the bottom either.... look like they'd throw off the reading a little bit Eric Baker's looks like it would look a little more accurate in that regard...

Eh... I made it big so that I could make fine tune adjustments. This is alot more accurate than most commercially available carb sync tools. I also think a basic understanding of physics would help dispell some of these myths about how "the first and last one were way off because of how the hoses are at the bottom, how they round".

 

[Rob Sherman]

Maybe someone else can chime in but I'm not feeling those connectors at the bottom either.... look like they'd throw off the reading a little bit Eric Baker's looks like it would look a little more accurate in that regard...

I thought the same thing.

Also, I think there is a reason they use mercury. I have no idea what it is though...

 

[Robb235]

I thought the same thing.

Also, I think there is a reason they use mercury. I have no idea what it is though...

Oil has a sensitivity 16 times greater than mercury allowing for better fine tuning, not to mention it won't harm your engine should you manage to suck some in.

Also, the reason mercury has been used is to determine the absolute vacuum measured in mmHg. We aren't interested in how much vacuum each carb/throttle body is drawing, but rather how much they are drawing in relationship to eachother.

 

[Azr6]

If you could make it smaller it would be pretty badass.

 

[DsmXsteve]

What did you do about the engine pulses... I built a 2 carb one once and it pulsed so bad it was too hard to really read

 

[Robb235]

If you could make it smaller it would be pretty badass.

You can make it as big or as small as you want. I just made mine big so that it would be really sensitive and allow me to get a really good sync on the tb's.

 

[Robb235]

What did you do about the engine pulses... I built a 2 carb one once and it pulsed so bad it was too hard to really read

I didn't have a problem with engine pulses. It vibrated slightly but nothing major.

 

[Azr6]

You can make it as big or as small as you want. I just made mine big so that it would be really sensitive and allow me to get a really good sync on the tb's.

So if you made a really small one it wouldn't be accurate right?

 

[DsmXsteve]

I think being as big as it is probably help it from pulsing really bad like mine did.. I only had about 15" of ATF in mine on each side so that really didnt have alot of head pressure to keep it from jumping all over the place

 

[Robb235]

So if you made a really small one it wouldn't be accurate right?

Yeah, something like that. On mine, the slightest turn on the adjustment screw could move the indicator up or down by 6" or more. Making it this big was probably over kill, but I wasn't sure how sensitive it would be my first time out.

 

[yzfr6chris]

robb235 does hose 1&2 and 3&4 have to be the same length where the oil evens out?