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Carb sync for dummies

  • Thread starter Thread starter claygs750e
  • Start date Start date
Ok, so I'm making a smidge of progress. I did find that even though I would run it on prime I still needed to suck on the vacuum line from time to time or the bike would die and would be out of gas. Not sure why since it's a brand new petcock. Oh well, so if you look at my very high tech temporary gas tank I rigged that up, things moved a long much better when I started using this. The gas still trickled out of the bottle and I would have to move the line a little to pour it into the carbs, but at least the bike stayed running so it must have been getting enough gas. Do I need some type of vent in the bottle to allow it to flow better?

So on to the sync...I know this is tricky and I'm new to this, but boy I think I make a little progress and then I get all bars all out of wack with just a few turns. I try to look at the bar for the 3rd carb and adjust the furthest away to that, but the third bar changes so it's difficult. One thing I noticed was if I hit the throttle it takes a second or two for the levels to come back down. Shouldn't the levels go back to the idle position almost immediately as soon as I let off the throttle? Also, after I tested everything for about 10 mins I shut the bike down to cool for about 5 mins and when I went to start with the choke off it just cranked and wouldn't start unless I pulled the choke.
 
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Ok so I'm still having problems with the sync and I need to clarify something. So if you look at the picture it seems that carb one even with the screw all the way out doesn't close all the way like the #2 and #4 butterfly adjustments. The problem I'm having is I can get it synced, but it's RPM is way too high with the idle knob all the way out. So I try to screw down and close the butterflys more, but the problem is the #1 carb I can't close any longer so that bar on the sync meter is way to high? Do I have a problem with that screw not allowing me to tighten as much as the others?

 
Yes you have a problem. They should all close tight if you wanted them to. Maybe this is the reason you are having so many issues getting the synch to stay put. Now what's causing this? not sure. Maybe someone that has had this issue can chime in. Does the butterfly on #1 seem to move freely enough, like the others? You know I can't help but think, weren't these carbs rebuilt by a "professional" shop? if so you really shouldn't be having any of these issues. Just as a though, looking at your picture it 'looks' like the spring and shaft on #1 is not up as high as the others (the spring under the adjusting nut), and it looks a bit bent. Play with it and make sure it's moving freely.
 
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I took it to cycle recycle and Rob who knows his stuff worked on the carbs, but only worked the float problem I was having and didn't even look at the butterflys. Yea, to me it looks like the spring on #1 isn't pushing it all the way closed. I realized I don't need them that closed, but when I'm syncing I need to close #1 more than it's allowing me to and it's causing the sync to be off. Nothing looks bent, but I wonder if I need to have the pring replaced?
 
Well done on perservering with your synch process even after it seems that everything that could go wrong, did go wrong! Ironically, this could be a positive thing, because now you are really learning how to work on your bike yourself, instead of having some "professional" shop working on it.

I mean, we all know these "professional" shops will do the job properly, right? WRONG! The only person who will do it properly is yourself!

I agree that something weird is causing that #1 butterfly to be more open than the others. Could it be a "mismatched" carb that has been added to the set? As mentioned, try bending the linkage a bit and look closely to see what could be causing the misalignment.

It looks like you only have this last hurdle to cross before getting this synch right. May I suggest a few things as well: (1) leave the pods on the carbs while doing the synch. (2) when you blip the throttle quickly, the levels on the gauges can take a few seconds to settle back down, due to the restrictors in the pipes. (3) referring to your hard starting problem after running for 10 minutes, it is OK to give some throttle to help it start when hot. It should not be necessary to pull the choke. (4) your valve clearances are set correctly, right? (5) you must adjust the synch screws in the correct sequence (unfortunately I do not have a manual here to tell you what the correct sequence is, but look it up or search on GSR).

Good luck in getting this right, I will watch your progress with interest!
 
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Can you post a pic of all 4 carbs straight on? Looks like the #2 carb is the one that's not closing in the pic above. Can't see what the state of #1, #4 are.
 
So I think I found the main issue I was dealing with and it's another pretty dumb mistake. Not realizing that the throttle cable was tight and slightly pulling on the butterflies is why I could sync them, but it was idling so high. So that gap on carb #1 isn't an issue since I don't need to have them that far closed now after loosening the cable.

UPDATE: SO I was able to drive to work today for the first time since putting the bike together and it ran strong. But, of course I was on the highway doing 55 for about 15 mins and then when I came on the off-ramp for a stop light it died and was very hesitant to start again. Luckily it started and I was able to get to work without having a heart attack! So it seems that when it's sitting still the idle seems perfect, but as I'm riding it if I come to a start the idle is higher than I want it so it seems like there are tweaks still to be made. Currently the mixture screw is 1.5 turns out. Any ideas?
 
Try setting the mixture screws at 2.5 turns out as a base setting for tweaking them.

Did you synch the carbs again after loosening the throttle cable?
 
Yea, after losening the cable I synced them and they all look great and I was actually able to ride it off and on all day yesterday. It was this morning after getting on the highway for the first time for 15 straight minutes is when it died. I think I'm only 1.5 turns out right now so maybe it's not getting enough fuel then? If I turn it back out to 2 turns, will I need to resync again?
 
No, turning the mixture screws does not effect the synch. At 1 1/2 turns it's probably a bit lean, you need to look at your plugs to determine if you are running lean or rich. Being a bit lean will not cause the bike to stall though, but it could be the cause of your bike idling a higher after being warmed up, that or you have a vacuum leak somewhere, intake o-rings, exhaust gaskets, etc... Is your petcock working properly?
 
I haven't checked for any leaks vacuum wise, but the petcock is brand-new. Now I do have a Dyno stage III kit with pods and four and one pipes. With the Dyno kit does that normally mean I need more turns out on the mixture screw or less?
 
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Ok, there is JUST ONE question and answer that hasn't been mentioned, or asked. Did you synch the synch gauge before hooking it up to the cylinders? There should be a small 5 port vaccum "tree" with it. You need to connect all four of the lines from the tool to it, and one to a vaccum source and synch the synch tool. If the levels of the tool are too low or too high to read well, you can adjust them to read as high or low as you wish. Then, and only then will that tool synch your carbs properly. You will have to do that to the tool each time you use it.

Also, 1.5 turns out is not enough. That WILL cause your dying at a stop symptom. Been there done that.

Also, with pods and a pipe, just throwing a stage 3 kit in the carbs doesn't mean it's going to be right, because the "other guys bike ran right like this".
Like a couple others keep saying, you need to pull your plugs and read them to SEE that it's right. Look up "plug chops" there will be a lot of threads about it.

Good luck, keep us posted...

If you really get bound up and can't get her right, there are MANY of us in your area that may be willing to give you a hand.
Great gathering of people here, super helpful...
 
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