Carb sync for dummies

[Charlie G]

Most people use a different temporary tank for syncing the carbs. The first time I did my 650 I did the same as you and set my tank on a stand next to the bike, but without a vacuum line to the "vacuum petcock" it won't open and send fuel to the carbs. http://www.thegsresources.com/_forum...highlight=newg
Note my thread, post 105, click on the small photo for short video. The grey metal bottle is my temporary fuel source. The vacuum port is plugged at the hose to the carb.

cg

[BigD_83]

I was told to plug the vacuum line with a golf tee when syncing. I can see gas going into the carbs. Before I start the bike I do suck on the vacuum line to get gas in the bowls first then let it hang loose.

If you are not running the tank on PRI, then it is entirely possible to run the bowls dry of gas, requiring priming again.

[claygs750e]

Well I'm an idiot again and that makes sense because it would run for awhile and then eventually die.. I could see gas in the line from the tank to the carbs and it seems like it was flowing. Looks like I'll have to make a temporary tank. Any other dumb mistakes people tend to make? would it be easier to just run it on prime? If I do make a temp tank am I just attaching it up high and relying on gravity only?

[BigD_83]

There are a lot of threads on temporary tanks, and some are ingeniously simple, if you have all of the bits and pieces kicking around. The advantage of using a temporary tank is that you don't run the risk of inadvertantly pulling your tank onto the floor.

You can run on PRI, but just like when parking your bike, you have to make sure you turn the valve to ON to stop the flow when you are not running the engine.

[Charlie G]

Well I'm an idiot again and that makes sense because it would run for awhile and then eventually die.. I could see gas in the line from the tank to the carbs and it seems like it was flowing. Looks like I'll have to make a temporary tank. Anyone have a picture of a simple setup and any other dumb mistakes I might make. would it be easier to just run it on prime?

You could run it on prime but I think it would be better and easier, since you have the tank there on a stand, to just hook up a vac line. My temp tank isn't a simple fabrication.

cg

[BigD_83]

Here's one thread of interest:

http://www.thegsresources.com/_forum/showthread.php?t=171591&highlight=Temporary

[claygs750e]

Because I already have the tank off and secure and have the hose I may just run it on prime. Isn't running it on prime and shutting it off when the engine is off the same as the temp tank and clamping the hose when the engine is off?

[BigD_83]

Because I already have the tank off and secure and have the hose I may just run it on prime. Isn't running it on prime and shutting it off when the engine is off the same as the temp tank and clamping the hose when the engine is off?

yes, no different.

Let us know how it goes.

[Charlie G]

Because I already have the tank off and secure and have the hose I may just run it on prime. Isn't running it on prime and shutting it off when the engine is off the same as the temp tank and clamping the hose when the engine is off?

Yes. I just got in from the garage and I wanted to empty a gas tank that had been setting for 7 years. I set it on a stand and turned it on prime. No gas. WTF. I stared intently at the petcock. What am I to do! I hooked up a short 1/4 line to the vacuum outlet on the petcock and sucked hard for a bit. The gas started flowing. Must have been stuck. Might happen to you.

cg

[BigD_83]

I've heard of that happening, Charlie. Might even have happened to me on that borrowed tank I had last summer...

[claygs750e]

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.

[claygs750e]

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?

[azr]

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.

[claygs750e]

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?

[2BRacing]

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!