I guess Im just not getting it..... I was reading through some forums, including this one, about tuning carbs. (Which I need done badly). Im no novice at this kind of thing, however I have owned a carb sync tool. Not having the tool anymore and not wanting to spend $100 on one, I decided to build my own from tutorials and explainations on many forums. I looked and studied how to do this and figured that If I made one (like they say) but making it with four tubes running into a resoviour of fluid, I would not only be able to sync carbs 1 & 2 together and 3 & 4 together, I would be able to sync the two banks together as well. This DID NOT work out. The vacume continued, like a staw, and sucked water the entire length of the 10' tubes. After cleaning the little water out of the carbs and getting it back to the way she was, I built another one, to specs, as I have seen. I capped carb 3 & 4, concentrating on carbs 1 & 2. Even with the looped end on the made tool, It sucked the water completly out. There are no leaks or holes in the tube and it did not work out the way it was explained.

Question: What am I doing wrong? was the four tube theory incorrect? and why did the written directions not work out?

Link to the tool: How to make a water manometer

Without looking at the link you posted, I would have to guess that you are not providing a tall enough water column in the manometer before it turns to horizontal tubing.


If memory serves, my bike pulls 8-10 mmHg at idle, and much more when snapping the throttle shut from high RPM. One mmHg equals about half an inch of water. This would mean that you would need a minimum of 16 to 20 inches of vertical water column to prevent water from being sucked out of the manometer, and into the bike.

It might be a lot easier to just go get the right sync tool.

No doubt! For all the time you've spent thus far in constructing a $100 tool, you're probably already getting paid less than minimum wage!

Actually, the problem would not be allowing a tall enough AIR column on top of the water column, before the tube turns down. Normal atmospheric pressure is about 30 inches of water column, so in a perfect vacuum you would need at least 30 inches of airspace between the water level and the top of the air column.

Note that manifold pressure is actually lowest (highest vacuum) at idle, and it is highest at wide open throttle, at low RPM.

+1. Takes a lot of ingenuity to develop your own tools. Time, too. Looks like MotionPro doesn't offer the Stix anymore Here's a link to a $114 tool:
http://www.carbtune.com/

Theres a shop in Alabama that had a set of Stix sitting on the shelf for years at $37.00. Might still have them (Midway Cycle Salvage, Madison, AL). Might be worth calling around to see if you can locate a set. Good luck with it, Z....