jonandjones
XS650 Enthusiast
I just got done rebuilding some different carbs for my bike. I can tell that the carbs are out of sync. I have made a manometer. Do you adjust the mix screws before you sync or after.
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carb adjustment whats first...
- Thread starter jonandjones
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- carburetors
Kind of a chicken and egg? Probably adjust the screws, do the synch and then readjust the screws. If you do a good eyeball synch you are likely to get em very close before they go on the bike. My method is to look through the intakes with a light source behind the carbs, adjsut the idle stop till there is the tineist sliver of light on the left carb adjust the synch screw till the right carb matches it, add back a turn or two of idle speed and install. This gets me within 1-3 psi on my gauges. It also confirms I have properly centered the butterflies after throttle shaft seal installation.
glennpd
4 bikes, 4 dogs, 1 wife
Another method of bench sync is to use a staightened paper clip as a feeler gauge. Using the idle speed screw determine the current setting by counting turns out until the screw tip just touches the carburetor shaft arm. Now turn the screw in until you can just slip the paper clip into the gap between the carburetor bore and the butterfly of the carburetor with the idle adjust screw. Now using the sync screw adjust the sync so that you can just slip the paper clip between the other carburetor bore and throttle plate. Now remove the paper clip and snap open and close the carburetor set a few times and double check. Once you are satisfied they are close re-adjust the idle speed screw to the previous setting.
If you are concerned with using a paper clip then use a plastic coffee stir or pretty much anything round, with consistent diameter firm of suitable size.
Glenn
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littlebill31
Smells of Raw Fuel
This is almost exactly how I do it. If you eyeball that little sliver of light to look just like a slight "smile" it works good.
I would like to add that my bike actually is not in sync. The right cylinder/carb is actually a little higher on the manometer scale than the left. I'm not sure what the problem is, but if they are perfectly even the right cylinder pops a little after getting up to temp. Once you do this a bunch of times and do the mix screw dance, then sync, then back to the mix you'll figure it out.
It won't hurt to test different settings either and I advise it. You never know.
BUT, make sure you keep the engine cool with either a fan or shutting it down to cool. Being new to this can make the adjustment take a while, so keep 'er cool.
jonandjones
XS650 Enthusiast
Thanks for the tips! I did bench sync the carbs as best I could before I put them on. I used the hole where the mix screw comes out for reference. The fluid at first tried to take off but a few adjustments and it stayed in the tubes. I can get it pretty close but not right on they stay pretty uniform then one side starts to climb a bit. So I thought maybe the mix needs to be adjusted on both then sync again.
The manometer is extremely sensitive and very accurate. Its normal for the 2 columns to move around slightly, so don't be too concerned.
