DIY carb sync tool

[manshack_one]

What do you guys make of this?

http://www.powerchutes.com/manometer.asp

Would build two for 4 cyl engines but the theory sounds solid.

[D. P. Larmee]

I don't think that this would work well for a four cylinder engine. If you look, it is one continuous tube. It would seem that each carb is fighting the suction of the opposite carb as opposed to just gravity as in the mercury sticks. It would seem possible that even if you had two sets, it would be possible to have two cylinders that were pulling stronger linked together and would look about the same as two weak cylinders linked together. I suppose that it would be possible to synch four carbs but I think that you would have to keep cross checking between the pairs to ensure that you don't get one pair that is pulling harder than the other.

[AlanB]

Hi Manshack,

There are lots of versions of this around; I am fairly new on this forum, but I bet I have seen more than a dozen on here!

They work OK, but are specifically for balancing TWO carbs; two sets would still not balance four carbs at once; only two pairs...... Go think about it!

However, it is possible to use them on a four....... idle stop on no3 is fixed, so you end up balancing 'em all to no3.

You set no4 same as 3, and then balance 1 and 2 so they match one another. The middle adjuster is then used to balance the two pairs to match one another.

It is easier to do than to explain; I am sure there are better descriptions on the forum already!LOL; LOL!

AlanB

[manshack_one]

I figured it might be worth a shot considering it's so cheap to build! I may try it out and see what I end up with unless I can get my hands on a borrowed manometer.

[81xsproject]

I use one similar with 2 sets of connected tubes. I do 1 and 2, then 3 and 4, then I disconnect them and hook up 1 and 4. It works WAY better than my vacuum gauge ever did as it is much more sensitive.

[manshack_one]

81, do you have pic or link to the one you used? Was it a DIY?

[trbig]

I kind of agree with D.P.

I think if you did this and had an open reservoir.. say a clear pop bottle where both tubes drew from and weren't dependant on each other for vacuum, it would work better. That way you'd know for sure of what each carb was drawing.

As far as that goes... it would be pretty simple to just stick 4 tubes into that bottle as it would be for 2?


Tod

[D. P. Larmee]

Yeah, doing it in blocks of two carbs at a time works okay, but it seems that most times it goes like this:

1) synch 1 to 2
2) synch 3 top 4
3) synch 1 and 2 to 3 and 4
4) 1 is no longer synched to 2, so redo it
5) 3 is no longer synched to 4, so redo it
6) synch 1 and 2 to 3 and 4
7) repeat steps 4-6 another couple of times untill everything is just right.

Maybe I'm just to nitpicky, but it seems that any adjustment to any of the carbs seems to throw all the rest off a bit. and it really helps to see the levels of all four at the same time to get it really dialed in.

[randy]

trbig;

Use that DIY synchro device with an open reservior and the fluid will get sucked into the engine. Not good.

[trbig]

Use that DIY synchro device with an open reservior and the fluid will get sucked into the engine. Not good.

I guess it would depend on how high your synch tool was. I have never tried it, but how many feet up a tube would it draw it? There isn't a lot of vacuum there. With the reservoir on the floor and the tubes going vertical for several feet, I wouldn't think it could draw the liquid that high... unless you blipped the throttle.


Tod

[81xsproject]

I have had one come loose before. I use pilot jets as pulse restrictors and I had plenty of time to see fluid slowly moving up the tube and reach over and hit the kill switch. No big deal. I would bet that it would take at least 15 to 30 seconds for the fluid to actually make it to the nipples. Now, if you are using water or another very low viscosity fluid you might be at a higher risk for a hydro-lock situation.

[Hired_Goon]

You can't have an open reservior as it will suck the oil/water up and into the carbs as it is working with pure vacuum rather than gravity.

Yes, they suck against the other carbs but when the oil is level in the tubes then your guaranteed that all four carbs are sucking equally.

I made one five years ago and it's what I tune all my bikes with. My XS11 idles very smoothly at 900RPM using this.

IMO, it is more accurate than four vacuum guages, but that's just my opinion.

Don't muck around with two tubes and swapping them over. Do it properly. It's amazing how a tiny twaek on one sync screw changes the other three carbs.

Spend ten cents more and make it like this.

[fredintoon]

That's the one!

Hired Goon's four-way is the way to go.
The lad's a genius. I've seen this style of manometer complifexed up with baby-food jars and I dunno what all but that simple cruciform is all the job needs. It's strictly a comparison gauge, it won't tell you what vacuum the carbs are pulling, just if they all pull the same, but that's all you need to know. Like 81xs sez, the thing needs flow restrictors but not necessarily pilot jets, some have used aquarium bubbler pinch valves, even. I'd say use ATF for the fluid.
It's a nice bright red, it's SG is 0.8 so it's a little more sensitive than coloured water, and if by some error it gets sucked into the engine, all that will happen is she'll smoke a little.

[Trikerneil]

Cheapskate!

Do the job properly

[manshack_one]

Hired_goon,

That's perfect! How long is each one of those strands of PVC? Did you number them or something so you always hook them up in order? And what kind of fluid did you put in yours? Also, are you using a flow restrictor like the other guys are talking about?

Thanks for all the info! DIY is the best!!