Ok so this may be a really stupid question but the guy selling the tool refuses to answer me, but anyways I'm wondering if a 4 gauge carb sync tool will work on twin carbs like my xs400. My reasoning behind buying the 4 gauge one is because my g-pa has a cb750 and was gonna use it for his bike also. I'm assuming that if you just don't hook up the other 2 gauges they would not get any pressure and therefore not get a reading...like I said maybe a dumb question. Thanks
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Carb sync tool?
- Thread starter boomer91
- Start date
A manometer is the only carb tool where it would matter. If you are getting a 4 dial air gauge then they are all separate from each other. A fluid gauge like a manometer or mercury gauge is much more accurate than any air/vacuum gauge. You can build a manometer for your twin for only a few bucks and it's simple to do.
yea look on youtube there's a couple of videos on how to make them! easy and super cheap, I honestly don't understand why people would buy the actual tool if they're not actual professional mechanics
I tried the air/vacuum gauge thing once. The needle just bounced around violently. It was impossible to get any sort of reading out of it.
angrybuddha
XS400 Member
I've had a proper 4 gauge vacuum balance tool for years and been worth every penny I paid for it (I did get it cheap tho). Was always balancing my 90s sports bikes and mates bikes too as they did seem to go outta sync when ridden hard.
The one I have has a valve on each input to the gauge to reduce the tube section so the needle slows down and moves slowly, works treat.
I tried to make a manometer from youtube and website info but it was a pain in the ass for a 4 pot bike and took up so much room I binned it and bought this one, never looked back
But everyone's experience is different?
The one I have has a valve on each input to the gauge to reduce the tube section so the needle slows down and moves slowly, works treat.
I tried to make a manometer from youtube and website info but it was a pain in the ass for a 4 pot bike and took up so much room I binned it and bought this one, never looked back
But everyone's experience is different?
Should be the first one the fuel flows into
Maybe I'm over-thinking this, but wouldn't the master carb be the one the throttle cable and the idle speed adjustment screw is directly attached to? The remaining carb(s) would all be "slaved" to this carb.
On a DOHC engine for example, this would be the right (#2) carb. The left (#1) carb is the slave, despite the fuel line connecting to it.
People often connect a small fuel bottle to the carbs, hung off the handle bar, and perform the syncing with the tank off the bike to gain the required clearance.
On a DOHC engine for example, this would be the right (#2) carb. The left (#1) carb is the slave, despite the fuel line connecting to it.
People often connect a small fuel bottle to the carbs, hung off the handle bar, and perform the syncing with the tank off the bike to gain the required clearance.
Yeah I just looked it up, it's normally the one with the idle screw.
Then how do you adjust the idle speed?
I don't know why you need a "master carb". The idle screw adjust both carbs. The sync screw adjust the throttle butterflies relative to each other. Just set the carbs so they have the same reading.
On a twin, it isn't that important. On a 4 or 6 cyl engine it is very important to have a starting point, the correct one! There has to be a master carb, and the rest are slaved off of it or synced to it. The master is typically the carb with the throttle cable and idle speed adjustment directly connected to it. The slave carbs are connected to the master carb by an adjustable linkage.
I understand that, but I was speaking in the context of an XS400. As to these little bikes, why make the process more complicated than it needs to be?
I got a free guage type sync tool after a buddy bought it so i could snyc his carbs. he also bought me the snyc tool for adjusting the screw and nut. along with a 90 degree screw driver for the ideal screw on some bikes. told him i would rebuild and bench sync his carbs for free so he told me it was my payment.
I looked at making the liquid filled sync tool using some clear hose and blue water. but it seemed to be a messy alternative. but i never tried.
the guages he bought were great and did not bounce around but the supplied valves are to reduce the gauge flutter. the gauges do have to be tuned before use. basically you adjust the needles to read the same thing without vaccum.
as for the fuel tank i used an old rear end oil bottle with a cutoff valve and filter in the middle. then i hung it with safety wire from the handle bars. you do have to add a vent so i bought a 1/2" replace vent for a fuel can.
carb have all types of different configuration so take the time to look at your carb or carbs and be familier before you being work. if you are not going to take the time to do so than you may be better off not messing with anything!
as far a which carb is the master, the master carb is the one which every carb "keys" to. so look at your carb and see how they are connected. most of the time this carb does not have a butterfly adjustment, other than a idle adjustment or slide adjustment.
and fuel can feed anywhere lost of multi carb units have cross feeds. and someone said something about why the carbs are not made togther or something, I think, well the reason is because the same design can fit many different bikes and may fit anywhere from a one carb set up to a four carb set up.
PS check this.
http://www.xs400.com/forum/showthread.php?t=6050
I looked at making the liquid filled sync tool using some clear hose and blue water. but it seemed to be a messy alternative. but i never tried.
the guages he bought were great and did not bounce around but the supplied valves are to reduce the gauge flutter. the gauges do have to be tuned before use. basically you adjust the needles to read the same thing without vaccum.
as for the fuel tank i used an old rear end oil bottle with a cutoff valve and filter in the middle. then i hung it with safety wire from the handle bars. you do have to add a vent so i bought a 1/2" replace vent for a fuel can.
carb have all types of different configuration so take the time to look at your carb or carbs and be familier before you being work. if you are not going to take the time to do so than you may be better off not messing with anything!
as far a which carb is the master, the master carb is the one which every carb "keys" to. so look at your carb and see how they are connected. most of the time this carb does not have a butterfly adjustment, other than a idle adjustment or slide adjustment.
and fuel can feed anywhere lost of multi carb units have cross feeds. and someone said something about why the carbs are not made togther or something, I think, well the reason is because the same design can fit many different bikes and may fit anywhere from a one carb set up to a four carb set up.
PS check this.
http://www.xs400.com/forum/showthread.php?t=6050
I'm not trying to be a jerk, or harass you, HM. I guess it is either the German heritage in me, or the aircraft mechanic training. Regardless, I believe there is a correct/approved procedure and every other way. That is not to say that other procedures are wrong. Knowing the proper procedure, or the theory behind it, makes it easier for people to make educated decisions. In this case, I don't think it makes it more complicated to use the correct procedure, and it may yield better results.
I also believe that the value of this forum is increased when the quality of the information posted is improved. Most of the members are new to motorcycles (myself included), many have never had any training or done any mechanical work. The knowledge we pass along may have a lasting effect on the members, long after they have moved on. Maybe I should have been a teacher...
