Carb Sync Observations

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BearOnt
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Carb Sync Observations

Post #1 by BearOnt » Tue Oct 17, 2006 9:41 pm

I bought myself a carb sync tool and put it to use today. :-D
I noticed a few things:
a) When you have one of the cylinders at exactly the right place it will move when you take the screwdriver off the adjusting screw. :shock:
b) Just because it was right a minute ago does not mean it will be right now. :-?
c) From idle to 3000rpm the difference is so great you wonder how it ever ran. :cry:
d) The warmer the engine gets the more frustrating this job gets. :evil: fly into a rage fly into a rage

I "think " I finally got it good. I would have to adjust it a bit high so it would be good when I removed my screwdriver. When I put the bike in 1st gear (bike on center stand) and reved it to 3000 rpm the levels in the sync tool seemed to calm down a fair bit and were easier to adjust. imsmilin

So the big question is: Shouldn't the bike be in gear under load to be able to accurately set the carbs? :?:

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heraldhamster
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Post #2 by heraldhamster » Thu Oct 19, 2006 12:50 pm

I'd wondered about this as well. I had a helluva time on mine...
but then I'm using a homemade sync with 5mm adaptors to do the job so I was expecting some frustration.

while we're here...
when adjusting mine between 2 & 4 or 3 & 4, it seems the level keeps rising/falling even after I stop moving the screw. once I get it stopped and they're still uneven, I adjust it ever so slightly back the other way and it keeps going the way it was. I'm confused. is there something wrong with my carbs?

please, from those of you who have done this a number of times... help and insight.

thanks!

...james.
sorta bulldogged custom 1978 GL1000 - "geekster" - daily rider
full Vetter dress 1979 GL1000 - "Barge" - daily rider (currently down)
1978 for $100 - project in worx
1978 from a previous member here - taking up space
my original '79 bought in '91 - replacing engine

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Post #3 by Frenchy » Thu Oct 19, 2006 2:49 pm

The bike needs to be at operating temperature when syncing. I let them idle until the the temp is well into the normal range before I hook up my gauges.

As for levels changing after you adjust, it has to (what I call) settle down for a minute... Remember, when you adjust one carb, you change the load on the motor. Thus changing the other carbs.......

James, throw away the home-made rig, & purchase an inexpensive set of mercury sticks!! Once the motor is at operating temperature, give yourself thirty minutes to an hour to get them synced... Plan on going around the bike a few times.. Also don't try to get them PERFECT! Get them close.... ;)
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Post #4 by Whiskerfish » Thu Oct 19, 2006 3:50 pm

Carb synch is almost an art when working with sloppy worn linkages and such, praying to the underworld gods may not be necessary but the blood of a live chicken can help!! One trick is to give the throttle a quick 1/4 turn snap after each adjustment to see what it does after it reseats itself. If working with Merc sticks use caution when doing this due to the sudden increase in vacuum when the engine is decellerating. I do that before I tighten the nut because that usually takes 2-3 tries for me to get it to stay where I want it while tightening the nut. I do not even know how many peices are in the throttle system between the grip and the actual carb but it is a bunch and any one of those with slop can make it very challenging.

Also a fan infront of the motor to keep things cool can be very usefull. As Frenchy states an hour of tweaking is not unusual to get them just so, but luckily it should only need to be done once a year or so.
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Post #5 by heraldhamster » Fri Oct 20, 2006 5:51 pm

Frenchy wrote:James, throw away the home-made rig, & purchase an inexpensive set of mercury sticks!!


dang, I knew you were gonna say that...

Frenchy wrote: Once the motor is at operating temperature, give yourself thirty minutes to an hour to get them synced...


it was definitely at operating temp, the fan kicked on several times, so I know that's all working correctly.

Whisker wrote:Carb synch is almost an art when working with sloppy worn linkages and such, praying to the underworld gods may not be necessary but the blood of a live chicken can help!!


I'm learning that. LOL! wow.

thanks to you both. I'll take it all under advisement. I've been trying to get away with cheap, homemade or 'on the fly'...
...james.
sorta bulldogged custom 1978 GL1000 - "geekster" - daily rider
full Vetter dress 1979 GL1000 - "Barge" - daily rider (currently down)
1978 for $100 - project in worx
1978 from a previous member here - taking up space
my original '79 bought in '91 - replacing engine

A gentleman is one who puts more into the world than he takes out. ~ George Bernard Shaw

A competent and self-confident person is incapable of jealousy in anything. Jealousy is invariably a symptom of neurotic insecurity. ~ Robert A. Heinlein

The good thing about science is that it's true whether or not you believe in it. ~ Neil deGrasse Tyson

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Carb synch

Post #6 by the chef » Fri Oct 20, 2006 9:36 pm

I just do them by" ear"...... takes a few times to get the feel of what you are looking for but I was able to hit it pretty close to perfect after stopping several ,several times and "fiddling" with the linkage screws. Just make sure you are happy with the way it idles and the top gear roll ons. Get rid of all the little backfires,pops etc. You can feel the pull and hear the hhhhooooooonnnnnnnnnnddddddddaaaaaa when you have it right! the chef
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Post #7 by halbritt » Sun Oct 22, 2006 5:29 pm

I have a carb sync tool (vacuum gauges and vacuum line) but I wonder where one gets the fittings to hook it up. Does anyone have any ideas?

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heraldhamster
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Post #8 by heraldhamster » Sun Oct 22, 2006 10:27 pm

sorta bulldogged custom 1978 GL1000 - "geekster" - daily rider
full Vetter dress 1979 GL1000 - "Barge" - daily rider (currently down)
1978 for $100 - project in worx
1978 from a previous member here - taking up space
my original '79 bought in '91 - replacing engine

A gentleman is one who puts more into the world than he takes out. ~ George Bernard Shaw

A competent and self-confident person is incapable of jealousy in anything. Jealousy is invariably a symptom of neurotic insecurity. ~ Robert A. Heinlein

The good thing about science is that it's true whether or not you believe in it. ~ Neil deGrasse Tyson

halbritt
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Post #9 by halbritt » Mon Oct 23, 2006 4:48 am

That's precisely what I was looking for, thanks.

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Post #10 by PJMehaffey » Wed Jul 01, 2009 10:42 am

Which size do you use on which bike?

GL1000?
GL1100?
GL1200?

5mm or 6mm?

Thanks

Patrick
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CYBORG
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Post #11 by CYBORG » Wed Jul 01, 2009 11:33 am

whiskerfish is my go to guy for carb. sync. he has done two of my bikes for me, and they have never been better. better then even when i thought i had them good. listen to him and learn. i did.
1978 custom GL1000
1977 custom with 1200 engine
1985 gl1200

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buzzinhalfdoz
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Post #12 by buzzinhalfdoz » Thu Jul 02, 2009 5:57 pm

my kit came with carb adptrs, hose , and 4 gauges, and 4 plastic shut off valves to go into the hose between the gauge and the carb(when adj right the needles stop bouncing around and settle to a constant number). i will agree dont try to get them perfect, just try to get them close.
yes the bike starts better and idles better and smoother. my first time it took about a hour, now about 20 min. i have used these on about a dozzen bikes now and my buddies cant believe the difference in smoothness at idle once adj correctly. i dont know how i made it so long without one.(my cousin bought mine (about 79.00) for doing some work on his bike for him.ps i broke one of the carb adptrs that screws into the intake, i made one out of a old long style main jet from another bike, same thread.
77 wing,barn find (7-9years),38,000 miles.slowly customizing, FIRST ride aug-09. 76 cb750f(830big bore kit),81gs750(with 1100 engine(1166kit),74 gt550 2-stroke.
ant life wonderfull ??

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syching

Post #13 by siebo » Sun Nov 15, 2009 12:59 am

I have mercury sticks, vacuum guages and the home set with atf fliud and yard stick. I found that when doing a carb set aftewr rebuild that I sych them close with guages or mercury that they are just that "close" when I use the cheapy yardstick< hose and trans fluid that I beleive I am getting them next to pefect. guages all have to be calibrated the same. with mercury you have to eye ball four levels. Homemade set I just have adjust vacuum between 2 carbs and make sure fluid level the same. do other 2 carbs same way then adjust from side to side same way. always works very, very well.
1984 gl1200 standard
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RB
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Post #14 by RB » Wed Dec 09, 2009 4:20 pm

OOPS
98 1500 SE..
99 1500 SE SOLD
97 SE 1500 SOLD
83 SOLD
82 REBUILT sold!!!
81 DAILY RIDER sold her :(((!
81 REBUILT SOLD!!!
81 REBUILT SOLD!!
80 REBUILT SOLD
79 IN BASKET PARTS FOR SALE
79 CLEANED UP AND SOLD
78 REBUILT SOLD
77 REBUILT SOLD
76 SOLD/PARTIAL REBUILD
76 REBUILT AND SOLD
75 REBUILT SOLD
75 REBUILT SOLD
75 REBUILD SOLD


FAIR WINDS,
RB

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gapl1953
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Re: Carb Sync Observations

Post #15 by gapl1953 » Wed Jul 14, 2010 11:12 pm

BearOnt wrote:I bought myself a carb sync tool and put it to use today. :-D
I noticed a few things:
a) When you have one of the cylinders at exactly the right place it will move when you take the screwdriver off the adjusting screw. :shock:
b) Just because it was right a minute ago does not mean it will be right now. :-?
c) From idle to 3000rpm the difference is so great you wonder how it ever ran. :cry:
d) The warmer the engine gets the more frustrating this job gets. :evil: fly into a rage fly into a rage

I "think " I finally got it good. I would have to adjust it a bit high so it would be good when I removed my screwdriver. When I put the bike in 1st gear (bike on center stand) and reved it to 3000 rpm the levels in the sync tool seemed to calm down a fair bit and were easier to adjust. imsmilin

So the big question is: Shouldn't the bike be in gear under load to be able to accurately set the carbs? :?:




Reading this cause me to chuckle! I just came in from the garage after experiancing this same thing on a GL1000 I just put back together after a valve job. I even used two different gauge sets. I know these things are touchy but come on I spent three hours on something that takes me about 45 min on average. imsmilin
Current Stable; 1979 GL1000, 1973 CB500K1, 1973 CB750K3, 1985 CB700SC, 1984 BMW R80RT,
1996 Buell S-2 Thunderbolt

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I say, "If it don't fit, get a bigger hammer"!


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