probably more accurate than gauges to be honest, as long as all the hoses are the same length and bottles are the same size, how can there possibly be any deviation?

Nope. The reason glass is used is because it will maintain it's shape under the relatively minor pressure generated by the carbs. Plastic is too weak, which is why you can deform a plastic bottle with your lungs. So basically, use a glass bottle.

GS 550 :)

BlizzardHockey4432 h

or you could just splice a used jet into each line (each jet must have the same orifice size opening) thereby reducing the volume of the fluid needed to effect observable change reducing the amount of vacuum needed to effect change. It just makes the device much more sensitive than using the full tube diameter, thats like swinging a tree as a fly swatter. Any little tube or reducer you can insert into the lines (remember ALL of them must be equal in I.D.) will do the the job.

That sounds more like a how do carbs work question and the internet can answer that query. Simple answer is the various needles and jets control the air/fuel mixture ratio.

+Maxim S. mean is it enouhg to connect just 1&2 2&3 3&4 with tubes without the "reservoir"?

+Maxim S. Functionally, yes, it is the same, but it makes it easier to fill the tubes with fluid and keep air out.

+kcorbings550 Thnx man!

+Photography.Naturally I used hex cap screws drilled through, with brass tubing pieces soldered to the head.

jeff i These do the same as any other manometer, perhaps even better since the deviation is minimal (assuming there are no air leaks). But this just cost around $10.- instead of $80.- for a set of gauges. Plus you have the satisfaction of being a DIY king. What I do miss in this video is at what rpm he does it and there's no warning for overheating air cooled engines while doing this.

+Roald van Dijken The RPM for syncing depends on the motorcycle model so always check your manual. This was between 1500 and 2100 RPM. Usually it will be slightly above idle. As a general warning, yes, always use a fan with air cooled engines when doing extended tuning sessions.

The 4 vacuum gauges would have to be calibrated to each other and have the same response curve but yes you could use 4 vacuum gauges if they were good quality and able to be calibrated. It's not really ideal because such gauges are expensive and sensitive. You have to really dampen the vacuum fluctuations otherwise the gauge needles will be wildly bouncing making them hard to accurately read and hard on the gauge itself.

Comercial dial vacuum gauges may not be accurate enough. You would not know the accuracy. For example one could be reading 5% high, another 5% low. With a fluid, it is perfectly accurate. The commercial ones with mercury would be nice, but expensive.

+jorge jimmy Canale ...un manometro decente (uno que no empiece a saltar por toda la escala haciendo de su uso un calvario) cuesta bastante mas dinero que la gasolina extra que se gaste respecto a este metodo.

jorge jimmy CANALE

+Dan Barclay Great point: once a bottle goes dry, it is possible to just keep running and open up another carb more to pull enough fluid back into the dry one. Preferably not your original reference lowest vacuum cylinder.

And I have never found such an accurate stable method where you can hear all the cylinders come in on song exactly according to the readings - unlike gauges that merely get close. Whilst not having to go to any great lengths checking the accuracy or setting up.

Extra points if you can come up with a method to eliminate the set-screw backlash so it's not as frustrating as... :-)

Carb Balancing is done to get the Vacuum between Cylinders to the same level at idle. You're basically synchronising the Carb Butterflies (in CV carbs), or the Slides (in Slide Carbs), so they all open exactly the same amount, for any given throttle position. A Water manometer will be more accurate than Mercury Vacuum Gauges or Dial types. You're not altering the Vacuum produced, you're just comparing between cylinders.

max vac is probably at full throttle.....this isnt about max vac this is about getting to all suck the same amounts at tickover and doesn't affect power or max flow etc at full throttle

John Doc. - balance at idle only - anything more is speculative

At idle the throttle's butterflies (or slides on older carbs) are limiting how much air can get into the intake track so the vacuum will be high. When you pull the throttle the butterflies open, allowing more air into the intake track and the pressure comes up closer to atmospheric pressure. Because valves always open the same amount (in non-variable valve lift/timing engines) it is the job of the throttle body to essentially "hold back" the engine by restricting the available air. Worn engines can actually be synced at idle and then come out of sync as they are revved because one cylinder is flowing better then others, usually due to dirt on intake valves. This isn't really an issue though as you tune each carb to its own cylinder. Syncing is really only important at idle because each cylinder is operating at the very bottom of its performance potential where any error means that a cylinder might not be getting any air at all and it won't be able to fire at idle.

Shed Man - Synced carbs probably move the same weight of fuel air mix.....the needles/pilots adjust the ratio of fuel to air. There is NO such thing as a PROPER sync gauge. I guess though you are referring to a damped diaphragm and spring gauge or a flow meter with damping - both of which leave the factory on Monday nominally reading some fictitious absolute air pressure measurement . By Tuesday, still in their packages they will no longer read the same nor again on the wednesday......too many variables eg phases of the moon, position of the tides, density of air, moisture content, internal friction, spring constants, damping rate, frequency response - to name but a few.......in other words NO WAY accurate. Ask yourself how an engine can suck blow bang on 720 degrees and the meters are set to give a steady reading....So why bother having 2 or 3 or 4 gauges when the only thing you hope to read is differential pressure Today. Tomorrow of course they will all be out of sync again as no carb will be linear and identical to its partner - the sun has only got to shine on the opposite side of the bike on the way home.....You make assumptions of what carb affect what in a group - so what when they are different (and all firing at different times)? You are only interested in getting them nominally the same on a day at tickover - the rest of the time it does not make one hoot of difference..... Your last line is a truism - as carbs usually share the same airbox

airleak? carbs are way out of balance - you have to adjust the highest bottles down as well as the lowest bottle up

Almorie Scholtz FYI, if you have a high performance vehicle you can eliminate many problems using glass bottles instead of plastic.

but viscous causes the fluid to climb the edges of the tube making it harder to read - it also slows the reaction of the fluids=inaccurate

It's sucking, not blowing.

you dont need to - just adjust the carbs till they level

Thats not what your boyfriend told me.