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First carb sync

  • Thread starter Thread starter Mickeymoe
  • Start date Start date
M

Mickeymoe

Guest
Well I'm all set to do my first carb sync, but I won't get to it until tomorrow evening. I also drilled out the plugs covering the mixture screws and will adjust them too. My question is, when do I adjust them for best running, before, after or during the sync? The .pdf says that adjusting the mixture will change the sync vaccuum, so which comes first, the chicken or the egg? Or do you just keep fine tuning both until the bike runs the best and the vacuums all match. Any tips would be appreciated. I don't expect this to produce a new bike, but it's GOT to run better than it does now....

And just to confirm, on a GS1000G, number one carb is the one on your left as when your sitting on the bike, right?

Thanks, Mark

carb_sych2.jpg
 
I normally adjust the sync first to make sure it's not way out, then adjust the mixture screws, then back to the sync.

Don't know how hot it is where you are but it's a good idea to run a fan in front of the engine so it doesn't overheat.
 
Theoretically, adjusting the mixture should not affect the sync at all. (I have never noticed it myself.) Yes, it will change the vacuum levels, but it will change ALL cylinders, not just one, like a sync adjustment will.

My usual practice is to start with a bench sync, if the carbs have been off the bike. If they have not left the bike, don't worry about that step, they are probably already close enough.
Warm the bike enough so that it does not need any "choke" to run.
Set the idle to just above 'normal' idle, or about 13-1500 RPM. (Suzuki manual calls for 1500-2000.)
Start by matching #2 to #3. They will fluctuate somewhat constantly, so match the averages.
Continue by matching #1 to #2. The manual calls for #1 to be just a bit higher, but nobody has come up with a decent reason why.
Finally, match #4 to #1.

You may have to adjust the idle speed occasionally while doing this, if the bike starts running better.

When you have all the carbs synchronized, adjust the mixtures. I usually start with all the screws 3 turns out. That give a mixture rich enough to run without "choke" sooner, but not so rich that it will foul the plugs. Start turning the mixture screw on #1 IN slowly. Listen for an increase in engine speed, which will also show as an increase in vacuum levels in all gauges. As you keep turning the screw, the mixture will eventually lean out to the point that the engine will slow down a bit. Stop, turn that screw back about 1/4 turn. Repeat for the rest of the carbs. When you have adjusted all of them, go back to #1, slowly turn it in, you should see that same drop at about 1/4 turn in. Turn it back out 1/8 turn, move on to the rest of them.

After making all the adjustments, verify a good mixture by blipping the throttle and observing the response. The engine should accelerate briskly, then return to idle smoothly and relatively quickly. If the return to idle is slow, maybe even 'hanging' foro a while, the mixture is a bit lean. If the return to idle dips below idle speed, then comes back up, it's a bit rich. Make adjustments in about 1/8 turn increments.

.
 
I just spent 10 minutes typing and was not logged in an lost the post. So I'll make it short now. The gauges I bought were practically useless- one didn't work at all and one was 50% off. The hoses melted, colapsed and disconnected from the gauge pack from the engine heat. I'm going to return the piece of crap tomorrow and buy a carb tune. Will have to do it all over again. The mixture screws made the RPMs DROP when I turned them in from 3 turns, so I left them at 3 turns. I think I may have the carbs somewhat synched now but I have a knock in the lower part of the engine at idle that I don't remember. It goes away if I give it even a tiny bit of gas off of idle. I'm hoping it's maybe the cam chain being loose and it tightens when the bike is reved a bit. I will check the adjustment on the cam chain tensioner.

Check the pick - the hoses can be seen melted and broken from what little heat was around theGUAGES2.jpg engine. Total junk.
 
The "tick" might be one carb out of sync. It might not be open far enough (high vacuum level), so the firing is uneven. As the slack in the drivetrain is taken up, it sounds like a tick.

Sorry you are having to go through all this. We usually recommend against the dial gauges for other reasons, we can now add "cheap hoses" to the list of reasons to avoid them.

It's a bit unusual to have the idle drop when the screws are turned in from three turns. Do you have them turned out three FULL 360-degree turns, or are they just three "flips" of the screwdriver? I have to ask, because I helped one guy over the phone and he insisted he had them three turns out. I went to his place to see what I could do, and found them out just 1 1/2 turns, or three "flips" of the screwdriver. Turned them out another 1 1/2 turns, his bike ran like it never had before. After tuning, they ended up about 2 1/4 turns out.

.
 
Is there any adjustment screw on those gauges? Normally with the more expensive types, you hook up each gauge individually to one carb and adjust it to the same pressure reading so you know all of them are correct.
 
I tried to buy a Carbtune directly from them, and found out the hard way that my credit union doesn't deal with overseas transactions and my accout was swiftly locked....
Ended up buying a mercury synch for dirt cheap. Its hoses are clear vinly and not so good. I have some silicone high temp hoses I found at a job and plan to use them next time.
 
Steve, I sure hope the "tick" is from an un-synced carb. You're correct it does sound more like a tick than a knock. The guages have no adjustments or screws to damp the needles. With regard to the mixture screws, I put a dot of yellow paint on top of the screwdriver handle and opened each screw 3x360 degrees on each carb. (COUNTERCLOCKWISE FROM CLOSED) I must have done this 4 times just to make sure. JUST TO CLARIFY, your info says to turn the screw "IN" until the engine runs faster. "IN" is CLOCKWISE....right? Maybe we should use CLOCKWISE AND COUNTER-CLOCKWISE instead of "IN" or "OUT".

When I turned the screws "IN" (clockwise), nothing happened for ~ the first turn, then the engine started to slow down so I turned it "OUT" conterclockwise back to 3 turns and left them there.

I wanted to get some riding in now that's it's cooled down but I'll loose the rest of the season at this rate. :(
 
Mickeymoe said:
The guages have no adjustments or screws to damp the needles.:(
Click to expand...

The clear cover over the face of each gauge will unscrew and come off. The straight slotted screw on the face of each gauge is an adjustment screw to calibrate all of the gauges to each other when you have them all connected to a single vacuum source. There also should be some plastic dampening "valves" that go in-line on each of the rubber tubes. The set I have looks just like yours except the brass adapters that screw into the bike are much longer, which keeps the tubes off of the motor.
 
jsandidge- The clear covers on mine just pull off (almost fall off). I know because one of the needles was stuck and it turned out that the needle had been mashed into the guage face with some force- there is a noticable crease in it. So after I fixed it I had no confidence in its performance. BTW, I just went and checked the box and found only 3 plastic damping "valves", loose, and one of them has no o-ring in it so it will leak (suck) air like crazy. And obviously I need 4 of them. I'm beginning to think that this "thing" that I bought is a knockoff of a similar looking unit that I've seen for sale at a slightly higher price, which has a brand name (can't remember) painted above the guages and comes in a nice case. Problem is, none of my hoses even TOUCHED the motor- the fittings themselves melted the ends of the hoses and just the radient heat from ~2 inches away calapsed other areas of the hoses. Also, I have those long tubes like you do also, they came with the kit, but are a different thread. (Likely for a Honda) I'm going to deal with the seller and likely Ebay to get this resolved and buy a quality tool as I should have done in the first place. It's such a cheap piece-o-junk that I'm sure the seller won't even want to spend the cost of a shipping label to send it back- he'll just say keep it or toss it.

I think it's a knockoff of this carb tool:
https://www.ebay.com/itm/Carburetor...ash=item58e1231019:g:IDgAAOSwLEtYgkkY&vxp=mtr

Mine is similar but came with no case, no stenciling, different (and missing) dampers, and chewing gum hoses. Probabaly overseas they take the rejects (like mine with the mashed dial) and sell them w/o the case etc. for less.




Mark
 
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