Carb bench sync question

[kgdb]

I have a question in regards to bench sync'ing 1980 GL1100 carbs.in the how to section here in regards to rebuilding 1100 carbs it says 'you will have to prop open the idle adjustment screw for this ' and then make the butterfly adjustment for number 3 carb. Why would one want to prop open the idle screw? And do you leave the screw propped open for the whole sync process? Seems I am not wrapping my ohead around this step. Appreciate your opinions.

Kgdb

[CYBORG]

i prop all the butter flies open a small amount by using the idle screw adjustment. this is to prevent the butter flies from bottoming out during adjustment. they must be able to move both directions. i measure the distance from the edge of the carb throat to the botom of the butter fly on #3, and then adjust the butter fly on #1 to be the same. then #2 to #4, etc. this gets me close enough to start and do a proper sync. and often is very close to right on. the pro's may chime in on this method, but it works for me

[fish]

I us e a small drill bit smaller that 1/16th
I adjust the idle screw untill the drill bit just slides in the butterfly in the #3
then I adjust the rest so the drill just fits.
This is a bench sync.
IF you have everything else right this will give a nearly perfect idle.
I do not own a sync gauge set. This system allways gets it close enough for me.

[kgdb]

Thanks for the replies. I wonder why in the article it says to prop the idle screw open and it looks like he is using a thin wooden paint brush handle, the he does the #3 Carb? Seems to me when you removed the prop the butterfly would be closed tight.

[CYBORG]

you would have to ask the person who said to do it that way. as you can see, there is no ONE right way. but the results are the same. all the butter flies are adjusted to the same opening distance.

[robin1731]

Be careful using anything metal, like a drill bit, under the butterflies. It is easy to damage them.

[hep2]

I use light inside #3 and adjust until the light is almost gone and then make the rest look the same and then keep going in a turn at a time on the idle screw until it idles, my sync was dam near dead on.

[Roady]

I'm guessing that you are working from the PDF of the instructions (my bad, that hasn't been updated). The proper way to bench sync was brought to my attention by Mike Nixon about a year ago and the thread was updated. Promise ... I'll fix the PDF.

Time to Bench Sync the set.

Previously, I had recommended Alley Kat's method of bench syncing the carbs by using a wire or needle as a feeler gauge. That was before Mike Nixon, noted GL Carb Guru, joined this board. He brought to my attention that the wire/needle method can cause "nicking of the throttle plate which permanently ruins the plate and introduces unregulated air". And you know that he's seen the guts of enough of these carbs to know what he's talking about.

So, how to get a decent bench sync? Simply look into and around the outlet port of #3 carb and locate the bypass outlet. It will be right along the line of the resting butterfly.



Note the relationship of the outlet to the edge of the butterfly. Now, adjust the 1/3 sync screw so that #1's butterfly position matches #3.

Flip 'round to the other side and adjust #2 and #4 so they match each other. Then adjust the left bank's sync screw so the 2&4 set match up to #3. The 2/4 sync screw is between those two carbs. The left side's screw is aft of #4 carb.

[kgdb]

Thank you. I found that updated sync process somewhere last night while surfing around. I assume this is done without the idle
screw being propped open? Thanks again

[Roady]

That is correct. The PDF has been updated.

Click Here to get the printer friendly PDF of Carb Overhaul, GL1100.

[kgdb]

Got a bit of tinker time in today. Did the bench sync and installed the carbs and crossed my fingers! Gave it some choke and hit the starter and it came to life. I tinkered with the idle little and then a bit more sync and it runs by itself. I will put the gauges on it in the coming days as it does need some more set up but for now it is running. Thanks all.

[robin1731]

Everything else, and I do mean everything, has to be right before you can sync the carbs. Timing must be on. Valve clearance checked. Engine up to operating temp. Then check the carb sync.

[CYBORG]

good to hear. what method did you use for the bench sync?

[kgdb]

good to hear. what method did you use for the bench sync?

I did the sync as Roady mentioned above and it fired up right away. Will dial everything in this week as I get the time but for now I am happy it is up and running.

[fish]

Everything else, and I do mean everything, has to be right before you can sync the carbs. Timing must be on. Valve clearance checked. Engine up to operating temp. Then check the carb sync.

even a careless job of spark plug gap can upset the synch.
This is why I quit worrying about it.
Seriously... how much time do I spend idling anyway?
Stoplights is about it. I set my idle a teensy high
1100RPM & that is just fine.