12.19.1. The $2.05 Carb Syncronizer (premium edition)

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Is there a carb sync tool?

From Ninja250Wiki

There are numerous tools which will help syncronize carburetors. These are all systems which will help you measure the difference in pressure between two (or more) carburetors. All are functional and accurate. There is no advantage to buying the commercial models except that then you don't have to make it yourself.

Note that the only other tool required to synchronize the carburetors on the Ninja 250 is a #2 Phillips screwdriver, ideally with a longish shaft (6" or more). You'll also need the tools necessary to remove the fuel tank, which can be found in the bike's toolkit.

Of the commercial tools available, the most commonly used devices are:

* Mercury carb sticks

* Twinmax electronic synchronizer

* Vacuum gauges

The "carb sticks" have the advantage that they're designed for four-cylinder motors, which is quite handy when working with other bikes with 3 or 4 cylinders. However, for the Ninja 250 (or any other twin), they're overkill. The Twinmax's main advantage is its easily modified sensitivity, but it's also dependent upon battery power and could be damaged if dropped or used in severe environments (the carb sticks suffer from these flaws as well). The Twinmax can be used with a 4 cylinder bike, but isn't as convenient, and may be impossible to use if the manufacturer specifies different pressures for each cylinder. The vacuum gauges are useful, but if mistreated will go out of adjustment, possibly without you knowing it. They are also highly dependent upon being set up correctly when manufactured.

However, a system for a two-cylinder engine is quite easy and extremely cheap to build at home. One type is this simple water manometer. Another is Payne's glass-bottle-based system, described below. Both of these systems are accurate, sensitive and require no calibration, as well as being durable and inexpensive to build.

Payne shows how to make your own carb sync device:

Honestly, officer, that's what it is! It's not a drug apparatus, I swear!

Image:Carb sync tool 1.jpg

The inspiration for this project came from a post a good while back, in which someone described this design using beer-making equipment. I finally made one, and I'm thrilled with it, as I always found the oil in the tube thing to be a pain and not terribly accurate. And I certainly did not want mercury sticks because of the toxicity and possible engine damage if it gets sucked in. And I didn't want to spend a lot of money on a tool I'll rarely use.


   * 2 empty glass Nantucket Nectar bottles (any similar GLASS bottle with a large neck should work)
   * 2 rubber stoppers ($2.50 each at Lowe's)
   * 10' 1/4" ID tubing ($2.00 at Lowe's)
   * Motor oil optional in place of the water 


   * Drill with 3/8" bit.
   * Pliers to pull hose through once it emerges.
   * Lubricant (I used cooking oil) to help get the tubing through the stoppers 

Drill two holes in each stopper; the rubber is a little difficult to drill through; you may try smaller drill bits first, working up in size as needed. One short piece of tubing goes through each and will go down to the bottom of each bottle. A long piece goes though each just enough to go into the bottle. Put about 2" of water in each bottle, not so much that if all the water goes into one bottle it will make it to the upper tube. Some people have found clean motor oil easier to work with than H2O.

Image:Carb sync tool 2.jpg

Image:Carb sync tool 3.jpg

Image:Carb sync tool 4.jpg

What happens is if one side pulls harder, the pressure will decrease in the upper portion of that bottle causing liquid from the other bottle to move through the transfer tube and raise the water level in that bottle. Since there can never be any liquid in the tubes connected to the carbs, there's no chance of the engine sucking in liquid. Plus, the movement is very easy to see and not jumpy, as can be the case with the oil in the tube trick. It's extremely easy to see in an instant which side is pulling harder and correct it. In my opinion, this is THE way to do this procedure. I think for the first time my carbs are truly synced. The way my bike runs backs that up; it idles and accelerates noticeably smoother.

Baby bottles also work well.

Image:Baby bottles.jpg

If you've looked around and can't find the hard rubber stoppers that are described in this article, here's another solution:

I just couldn't locate black rubber stoppers... I could easily get the white rubber "gum" stoppers (I'm a home brewer)... but they are much softer. Therefore, the first drilling attempt resulted in some fairly mangled-looking rubber chunkage.

Now, you can buy stoppers with 2 holes in them already, but you'll probably have to go to an online lab supply, and they typically sell by the pound. Eek! So, I was tinkering in the garage one day and realized I had some leftover 3/16" rigid brake line which would fit nicely inside the 1/4" clear tubing.

I returned from the home brew shop with 2 more #6 1/2 stoppers for my Welch's grape drink bottles and put them in the freezer overnight. The next day I drilled them with a 3/16" bit. Freezing made a huge difference. I cut four 2" lengths of the 3/16" brake line. A small squirt of oil in each hole and some light tapping with a hammer drove the 4 tubes in the four holes of the two stoppers. Cut the vinyl tubing to length and stick it on the rigid tubing snuggly and you're done.

Total mod time: about 20 minutes


Two #6 1/2 White Rubber "Gum" Stoppers

Image:Gum rubber stoppers 1.jpg

Drilling holes into "frozen" stoppers with a 3/16" bit

Image:Gum rubber stoppers 2.jpg

Rigid 3/16" brake line snuggly inserted

Image:Gum rubber stoppers 3.jpg

Project completed... just add liquid!

Image:Gum rubber stoppers 4.jpg

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