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Synching question

  • Thread starter Thread starter Anonymous
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Anonymous

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I finally received my valve shim tool and mercury synching tool from JC Whitney.

I adjusted my valves. All exhaust and one intake were too tight.

Then today I synchronized my carbs. I got all of the carbs as close to the same as I could. My question is, should the mercury stay fairly still or should it pulse up and down. Mine pulsed, and none of the mercury tubes pulsed exactly the same at all times. So when I say I got it as close as possible, I mean each tube stayed pretty much in the same area. When finished all of the mercury hovered around 17 inches of vacuum.

If I started with one carb and raised the vacuum a few inches, and then tried to adjust each of the other carbs to the first carb, would the mercury even out more?

Thanks,
Billy
 
After synching my carbs earlier, I had to run a few errands. I was able to go out and run my bike again about a half hour ago. Now there are problems present that were not there before. Actually the bike was running pretty well before I synchronised the carbs.

My problems are:
unless I set the idle high (above 2000 rpm) the bike will steadily idle down and die.
the vent tube for carb #1 is steadily releasing fuel, it did not do this before the carb synch. When the synchroniser was first hooked up, before I adjusted anything, carb #1 was pulling about 3 times the vacuum that the other carbs were.


Even before the synch my engine seemed to be running hot, but I couldn't seem to fix it. Now however, after only running it a few minutes, I couldn't even touch the points or there backing plates.

Another problem that started just recently. With my bike running, if I open the choke all the way it idles down, close the choke sightly and my idle rises to about 4000 rpm. Close the choke a little more and it starts to idle down. Then about the last 1/16" to 1/4" of travel to fully closed raises the idle slightly.


Once again I am without any ideas, my poor :( GS550E :cry: seems to want to do everything the opposite of what it should.
As always I appreciate all ideas and speculation,
Billy Miles
 
I got this from motorcyclepro ??? one of the other sites I forget which one If you are going to run the bike IT helps if you can put a house box fan to blow air over he engine while you are working on it


Balancing your Carburetors



What does "balancing" mean and why do I need to do it to my bike?

Balancing keeps each carburetor working the same amount to deliver the same amount and mixture of gas and air to each cylinder. We determine how "hard" each cylinder is working by measuring the vacuum at each of the carburetors which is provided by the downward motion of the cylinders on the first of the 4 strokes(the opposite of the compression that takes place in the cylinders on the 2nd stroke). There is a pressure "drop" that occurs as you pass by the butterfly throttle valve (the flat circular piece that pivots about its center when you move the throttle grip). The throttle valve will never close all the way - or else the engine would die without another source of air. What balancing does is to make sure that each throttle valve on each carb is allowing the same pressure drop to occur, therefore "sucking" the same amount of gas up through the jets.



OK -now how do I do this?

Each bike is a little different, so I'll try to be general, but keep it specific enough so that you have a clue as to what I'm talking about.

The first thing you'll need to do is to print this page out (unless you have a service manual that will step you through the process). Before you gather your tools up - you will need a set of VACUUM GAUGES. There are basically two different types - the dial type and the mercury type. Sure, you can get good and bad mercury-type gauges, but unless you're planning on really going into business for yourself, the cheaper mercury-type gauges are probably your best bet. You can order them from a number of sources including Dennis Kirk and J.C. Whitney in Chicago - ask for a motorcycle catalog (312)431-6102. When you order the gauges, tell the supplier what kind of motorcycle you have and ask them if you need any special adapters to use the gauge (if you do - it's usually just an extra few bucks).


Now that you've got your balancing "sticks" let's get down to it

Ride the bike around for just a couple of minutes to warm it up. Next, shut the bike off and put it on its center stand.
Disconnect the vacuum line (the small hose) to your fuel tap.
Take the gas tank off. If you can leave the gas line connected and still take the tank off, do so, if not - you'll have to find another container to feed the gas to the carbs. I've heard of people using inverted plastic bottles (thouroughly washed out) with some sort of tapered top to them. Connect the fuel line to the tapered tip, fill the container, invert it, and then poke a small hole in the bottom (which is now up in the air) to allow air to get in, and stick it somewhere above the carbs.
Now there should be one small rubber vacuum tube connected to one of the "nipples" that are either in between the carbs and the engine or they may be on the side of the carbs facing the engine. Pull that end of the small vacuum hose off (the other end was connected to the fuel tap-and you just took that off). You now will need to remove the other vacuum "caps" on each of the carb "nipples" that are in the same place as the hose connection for the fuel tap vacuum line (on the other carbs).The vacuum port caps are usually rubber and either pull off by hand, or with a pair of needle-nose pliers (there may be a clip that holds them in place).
Alright - now you have 4 little tubes or small pipes sticking out from or near the carbs. Next, connect the vacuum gauge lines to each of your carb vacuum nipples. Make sure the tubes are attached tightly, and that there won't be any air leaks.
Next - start the bike without revving the engine above 3,000 rpm or so!!! Actually, opening the throttle doesn't create a big vacuum - but if the engine is running fast, slamming the throttle closed will create a momentary high vacuum situation that might suck mercury into the combustion chambers. That is a REALLY BAD THING - mercury vapor is extremely TOXIC and exposure to it in sufficient quantities and for a certain time has shown to cause brain damage. SO...... don't slam the throttle closed when the gauges are hooked up and the engine is running.


Ok, gauges hooked up, engine warm and running......


Set the idle to spec (or thereabouts)
Look at the gauge - the quantity (usually measured in millimeters or inches of mercury) of vacuum is not nearly as important as whether all of the carbs are pulling the SAME vacuum.
So - to balance them, you will be "finely" adjusting the position of the throttling valves in each of the carbs. If you don't have a manual to show you where the adjusting screws (and locknuts, usually) are, open and close the throttle SLOWLY while you are looking at the carb assembly. Specifically, look inbetween each of the carbs for where they are interconnected - there will be some sort of screw or bolt that you can turn to adjust them.
If you have a 2 cylinder bike, you've only got ONE screw/bolt/locknut to deal with - so loosen the locknut and try turning the screw in either direction until you see that the mercury levels are about the same.
If you have a 4 cylinder bike, you will have THREE screws/bolts/locknuts to adjust. Start by adjusting the screw inbetween the #1 and #2 carbs (counting from either side is OK). Turn the screw until the #1 and #2 carbs are reading about the same vacuum. Now move on to the screw inbetween the #3 and #4 carbs. Balance the #3 to the #4 carb. Lastly - turn the screw in the middle to adjust the #1 & #2 carbs to the #3 & #4 carbs.
Now SLOWLY open and close the throttle a few times, each time bringing the bike over about 3,000 rmps.
Recheck the balancing, and repeat the procedure until each carb is within about a quarter to half inch of the others.



When you're all done, shut the bike off, remove the vacuum gauges, and put everything that you took off, back on. If your carbs were out of balance you will
notice the difference in power and / or gas milage.
 
Thanks SqDancerLynn1, I did follow my Clymer manual to synch my carbs, amd I did get them between 1/4 inches and 1/2 inches of each other. So I now know that they are synched properly, but why would my other problem suddenly appear?
 
Personally I would go back an recheck your work, First It sounds like you need to check the floats/needles also on #1 carb
 
SDLynn, pretty good recipe for balancing. The only general modification I'd make to it should also solve the mercury bounce problem: instead of setting the idle to factory spec's, bump it up a 1,000 or so RPM. This smooths out the levels in the stix. I can only speak for my 1100, but the shop manual calls for an RPM setting of about 1,700 for synchronizing. It's real easy to do this by using the throttle cable adjuster near the hand grip. Just remember to reset the cable adjuster when done.
 
with my carbs number three is the carb you set the other ones to match. I thought that was the way it was for all the suzuki's. I recomend syncing the carbs closer to the rpm you drive most at. I do mine at 3500. with a little practice you can get the mercury flat. if you get air bubbles in the merc undo the hose attached to the manifold and gently blow into the tube.The difference between having them close and spot on is important. once you get them right the motor is smooth as silk in comparision and you will see a hp increase at lower rpm I use a Motion Pro merc sync i got from JCwhitney is that what you have?
 
thanks skip I will try that. Yes I have the same synchroniser.
 
Thanx, Skip. Never tried the higher RPM; I just blindly followed the manual. Next time I'll try it. I really just wanted to reinforce "Close enough is not good enough". It really is time well spent to get all carbs as close as possible.
 
The first, and only time I did my carbs, I forgot to unplug the little vents on each of the mercury columns and in retrospect I think this is what made the readings very jumpy. I got them all close but I'm sure they could be better. So make sure the rubber vents on the tool are open while synching
 
78gs550 said:
Another problem that started just recently. With my bike running, if I open the choke all the way it idles down, close the choke sightly and my idle rises to about 4000 rpm. Close the choke a little more and it starts to idle down. Then about the last 1/16" to 1/4" of travel to fully closed raises the idle slightly.
Click to expand...

The choke operation doesn't sound too far from normal. If you have the choke way open, the mixture may be too rich. As far as I know, it's normal to have the idle increase initially pushing the choke in from wide open. At some point, the engine reaches an "optimal" setting where the RPM peaks, and then it comes down from there. I can't explain the slight rise at the end, though. How slight is it?

Michael
 
The long explanation by motorcyclepro completely ignores 1 important fact about the VM Suzuki carbs: the petcock vacuum comes from the #3 carb and has to be plugged! He also doesn't realize that the mercury will be OK snapping the throttle closed IF there is adequate mercury in the resevoir. Start and slightly warm up the motor before attaching the gauges - this way you will avoid the dreaded 'spit' backfire which blows mercury out of the gauges. A good test of the boots is to rock the carbs while hooked up to the gauges - you can actually see dramatic losses of vacuum.
 
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