how to sync carbs using eyeballs only?

[kml.krk]

I think I saw once someone mentioned doing that. If I am not mistaken it was Buddha 

Is it possible? If yes then how can I do it? How accurate is it?

PS. I once built syncing machine (aquarium hose, with water inside, stapled to the wood) but it was not working very well 

thanks
KML

[ineedanap]

You can kind of eyeball them to make sure they're both open the same amount while the carbs are off the bike.  (after rebuild for example)  I've heard it referred to as "bench sync" and it's not that accurate.  It's good enough to get the bike running, but you still should sync the carbs the right way.  

I'm surprised your syncing machine didn't work for you, here's how I do it and it works great every time.

I use about 4 feet of clear tubing filled with about 1 foot of oil (it's thicker than water and doesn't jump around as fast).  Use a size that will fit on the nipples on the top of the carb.  
Get bike all the way to operating temperature.
Remove fuel tank.  
Hook one end to the top of one carb, the other end to the other carb.  (where the rubber cap is on the very top)
Allow the hose to hang like a U, with the oil in the bottom.
Start the bike.  
Oil will move towards the carb that is seeing more engine vacuum.  
Shut off bike.  
Turn the sync screw one way.  
Start bike and see if you made it worse or better.
Shut off bike.
Turn sync screw whatever way you need to.
Start bike (you get the idea)
Repeat until oil doesn't move in either direction.

By far the easiest way to sync twin carbs, and cheap too.  You can leave it running but you only have a limited supply of fuel in the carb (tank is off) so work fast!

[kml.krk]

thanks for help!
this is pretty much what I have been doing   
I got them (carbs) not to suck the fluid into them but the fluid was never perfectly leveled like I thought it was supposed to be 

On the video I watched the guy managed to get the fluid calm as the wind before the storm  so I was going for the same but no luck.

I will try again with bigger diameter hoses and oil inside so it won't be that "jumpy"

[The Buddha]

I look at a nice area by the sun and match the amount of daylight comming through each.
A nice white cloud works well.
Cool.
Buddha.

[kml.krk]

thanks Buddha.
after all I am not crazy

do you have any idea how accurate it is VS the yard stick method?  (please just don't say: "as accurate as your vision is"  )

[Ry_Guy]

PS. I once built syncing machine (aquarium hose, with water inside, stapled to the wood) but it was not working very well 

just curious....are you firing on both cylinders when at idle?

[ohgood]

You can kind of eyeball them to make sure they're both open the same amount while the carbs are off the bike.  (after rebuild for example)  I've heard it referred to as "bench sync" and it's not that accurate.  It's good enough to get the bike running, but you still should sync the carbs the right way.  

I'm surprised your syncing machine didn't work for you, here's how I do it and it works great every time.

I use about 4 feet of clear tubing filled with about 1 foot of oil (it's thicker than water and doesn't jump around as fast).  Use a size that will fit on the nipples on the top of the carb.  
Get bike all the way to operating temperature.
Remove fuel tank.  
Hook one end to the top of one carb, the other end to the other carb.  (where the rubber cap is on the very top)
Allow the hose to hang like a U, with the oil in the bottom.
Start the bike.  
Oil will move towards the carb that is seeing more engine vacuum.  
Shut off bike.  
Turn the sync screw one way.  
Start bike and see if you made it worse or better.
Shut off bike.
Turn sync screw whatever way you need to.
Start bike (you get the idea)
Repeat until oil doesn't move in either direction.

By far the easiest way to sync twin carbs, and cheap too.  You can leave it running but you only have a limited supply of fuel in the carb (tank is off) so work fast!

buy an extra 10 feet or so of flex hose, and you can siphon from your tank, wherever it's sitting.

[AccidentalF]

I've "bench synched" old mechanical slide carbs via the manual with feeler gauges...but butterfly carbs wouldnt really work the same way unless you had some wire-type gauges, and those are rare i think.  Besides, benching carbs ASSUMES that all the cylinders are running the same compression, that the valves are exactly set and identical across cylinders...too much guesswork.  Thats why they make manometers.

[GeeP]

PS. I once built syncing machine (aquarium hose, with water inside, stapled to the wood) but it was not working very well 

thanks
KML

Why wasn't it working for you?

That's the way I've always done it. 

[kml.krk]

PS. I once built syncing machine (aquarium hose, with water inside, stapled to the wood) but it was not working very well 

thanks
KML

Why wasn't it working for you?

That's the way I've always done it. 

I think I used too small diameter hose and the devicewas too sensitive. I will be repeating the procedure on Monday with larger diameter hose.

[kml.krk]

PS. I once built syncing machine (aquarium hose, with water inside, stapled to the wood) but it was not working very well 

just curious....are you firing on both cylinders when at idle?

well, I think so. The bike runs fine overall. How can I make sure that both are firing at idle?

[Ry_Guy]

pull one of the plug wires off a spark plug while it's running. It should still run on the other cylinder, and vice versa. If it kills, your're only idling on one cylinder. I only ask this of you because I'm having the same issues with my carb synch tool, and wonder if there is any coorelation.

[intergalactic]

I check the relative balance at idle with header temperature. The 'point and shoot' IR temperature sensors are cheap these days. So I can tell if one runs hotter or cooler at idle. My cheap ($10) one only goes to $600F or so, so it only works at lower throttle settings.

I know I have an intake valve lash mismatch. .0025 versus .0010" it still seems to run on both cylinders. But differently at different engine temps.

I would love a fuel injected GS500.

[kml.krk]

pull one of the plug wires off a spark plug while it's running. It should still run on the other cylinder, and vice versa. If it kills, your're only idling on one cylinder. I only ask this of you because I'm having the same issues with my carb synch tool, and wonder if there is any coorelation.

will do tomorrow!

[the mole]

how to sync carbs using eyeballs only?

Best way is to remove the carbs and sit them on the bench with intakes facing up. Sit one eyeball in each intake and slowly open the throttle. If both eyeballs drop at the same time, its in sync.
NB. You have to get well matched eyeballs. 

[kml.krk]

success!!

I built a new carb balancing tool today and had success using it!
I know what my problem was before:
1. I used to small diameter hose
2. I did not use the T-Valve so the device was extremely sensitive making it impossible to sync

I fixed those issues and succesfully balanced carbs, although I still did not use the T-Valve, because I do not have one.
I used vice grip instead to squeeze the hoses during start-up and then slowly let go off the grip.

The device was still quite sensitive, because of the lack of T-Valve but at least it worked!

I have one more question though.
I noticed that the balancing screw is extremely sensitive - turning it even a tiny bit (1/32 of a turn) produces major vacuum change. Is it normal??

[commuterdude]

I pulled the carbs and feeler gauged the one side which showed a crack of daylight closed.   Then i closed the other side on the gauge till I got the same drag.