Carb Sync Tool

grizztracks · Jan 22, 2012

I made my own sync tool out of 12' of 5/16" vinyl tube filled with a little transmission fluid. I mounted the tube in a "U" shape on a 4' 1X4 pine board and filled it so I had around 22" of fluid in each side of the "U". You can only sync two carbs at a time but I've had good results with it. #3 carb (stator side) is preset so you sync 1 and 2 to it. There are only two screws to adjust (3 screws on 4 cylinder engines) which are located between 1-2 and 2-3. It's an easy adjustment that can make a big difference in performance.

Here are a few pictures of my Carb Sync Tool and it being used to sync the carbs on a Vector.
Note: never run the engine with only one side of the sync tool connected or you'll suck the oil out of the tube.

Hose connections are shown for adjusting carb #2 to the preset carb #3.
For this configurations adjust screw #2 until the sync tool is balanced then reinstall #2 fuel pump vacuum hose to the carb.
Move the T-hose over to #1 carb , reconnect the #1 fuel pump vacuum hose to the "T" and sync #1 carb to #3 preset carb by adjusting the #1 screw.

Carb #2 out of sync

Carb #1 slightly out of sync

Sync'd carb

TOMBOB · Jan 27, 2012

GRIZZTRACKS,
quesstions
1. is 12 ft of hose total or for one side or booth

2. at what speed do you test idle /wot

3.do you fill the tube up to 22" +/-

4. sync two carb's to 3rd at the all same height

5. 5/16 hose o.s.----?

thanks for all infor you give for this site

TOMBOB

TOMBOB · Jan 27, 2012

GRIZZTRACKS,
43 degrees in michigan today so made your sync tool. less than twenty buck. booth 1&2 carb were out of sync. very simple idea but very effective.

thank again, very helpful

TOMBOB

aVenture · Jan 27, 2012

This differential type of guage always worked good for me, compared to the absolute type sold on the market. It is very sensitive, and contrary to a absolute connection, you can give it some gas after equalizing carbs so to have a feel how close the slides are opening together. All in all, this is not an absolute reading you need but the difference between cylinders, and it does it more precisely. The industrial one i bought for my bike has been collecting dust.

Oh.... i use antifreeze..

grizztracks · Feb 1, 2012

TOMBOB said:
GRIZZTRACKS,
43 degrees in michigan today so made your sync tool. less than twenty buck. booth 1&2 carb were out of sync. very simple idea but very effective.

thank again, very helpful

TOMBOB

Sorry I didn't get a chance to answer your questions before you put together the sync tool.

I used 12' total of 5/16 O.D. tubing which is just enough to mount it on the board and still reach the carb's. I cut about 4-5" off one end of the tube and inserted a tee for the fuel pump hose which is removed from the carb being sync'd.

I filled the tube with transmission fluid so that both sides have about 22" of fluid measured from the bottom of the "U". I found it easier to actually suck the transmission fluid into the line rather than trying to pour it in.

Syncing the carb's should be done at an idle with the engine at operating temperature (1350-1400 rpm). After each carb adjustment bring the engine rpm up then allow it to return to idle so that the carb settles. This is a differential type sync tool so all that matters when making an adjustment is that the fluid is level in both sides of the tube which indicates that the two carbs are balanced.

4strokeluvr111 · Feb 6, 2012

IMO....anybody with a carb'd Vector (any carb'd Yamaha 4S???) that likes to tinker even a little bit on their sled should build one of these!

Easy to build and use. The hardest thing was getting the right amount of tranny fluid in! :o|

Thanks Grizz! ;)!

Horizonls · Feb 23, 2012

How would you proceed to syn an Rx-1 with 4 carbs, only two carbs have the vac lines attached to them and the other two are capped off?

grizztracks · Feb 23, 2012

If a carb has a vacuum line for the fuel pump pull it and reconnect it to the tee in the sync tool line. If their is no vacuum line then pull the cap off, connect the sync tool and then use the cap to plug the tee in the sync tool line.

theewarrior · Jan 11, 2013

All I can say is this works ....thank you!!!

gosnek · Jan 12, 2013

Made one of these today,did a super clean on carbs was still having some issue, warmed up sled and hooked it up carbs where out of sync man what a difference after the sync. This site rocks :rocks:

grizztracks · Jan 13, 2013

Glad I could help ;)!

Bradford · Feb 6, 2013

I built one of these too. The only differnece is I used 2-smoke oil instead of transmission fluid. Finally found a use for that oil!

vetcorman05 · Dec 14, 2014

How important is it that it is 22 inches of fluid? Or is any amount ok? i made one today and was having a hell of s time getting 22 inches in the tube.

grizztracks · Dec 14, 2014

the actual amount of fluid isn't critical. I sucked the fluid into the tube.

vetcorman05 · Dec 15, 2014

Thanks grizz,I didn't think so and was hoping not,either I got way to much or not enough. Other than I think I have something else going on,it worked great.

Carb Sync Tool

grizztracks

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TOMBOB

TY 4 Stroke Junkie

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aVenture

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Horizonls

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gosnek

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Bradford

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vetcorman05

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