Carb Sync Observations

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BearOnt
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Carb Sync Observations

#1

Post by BearOnt »

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? :?:
heraldhamster
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#2

Post by heraldhamster »

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"
full Vetter dress 1979 GL1000 - "Barge" (currently down)
1986 1200 Aspencade - "Heart of Gold" - daily rider
1990 1500 Aspencade - It's ALIVE! but very, very naked. not in a good way.
1978 for $100 - project in worx
1978 from a previous member here - taking up space
my original '79 bought in '91 - replacing engine (eventually, maybe someday)

H2G2=42

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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#3

Post by Frenchy »

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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#4

Post by Whiskerfish »

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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heraldhamster
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#5

Post by heraldhamster »

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"
full Vetter dress 1979 GL1000 - "Barge" (currently down)
1986 1200 Aspencade - "Heart of Gold" - daily rider
1990 1500 Aspencade - It's ALIVE! but very, very naked. not in a good way.
1978 for $100 - project in worx
1978 from a previous member here - taking up space
my original '79 bought in '91 - replacing engine (eventually, maybe someday)

H2G2=42

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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the chef
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Carb synch

#6

Post by the chef »

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
On the highway to Hell!
Ride on, Ride on.. !
PREVIOUS OLD LOVES=
19?? Zundapp with 6 hp Briggs and Stratton engine Chrome tank
1971 Kawasaki H1 500 blue /white stripe
1975 Honda 750 Yellow
1980 Honda Gl 1100 Interstate Black
1982 Honda Gl 1100 Standard Black
1983 Honda Gl 1100 Aspencade Black
1981 Honda Interstate Black
1981 Honda Gl 500 Silverwing . Candy muse red
1986 Honda VT 500C red
PRESENT RIDE >1976 Honda Gl 1000 Originally red, now flat black, olive drab, primer gray.
halbritt
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#7

Post by halbritt »

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?
heraldhamster
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#8

Post by heraldhamster »

this is where I got mine:
http://www.motionpro.com/motorcycle/too ... _adapters/

...james.
sorta bulldogged custom 1978 GL1000 - "geekster"
full Vetter dress 1979 GL1000 - "Barge" (currently down)
1986 1200 Aspencade - "Heart of Gold" - daily rider
1990 1500 Aspencade - It's ALIVE! but very, very naked. not in a good way.
1978 for $100 - project in worx
1978 from a previous member here - taking up space
my original '79 bought in '91 - replacing engine (eventually, maybe someday)

H2G2=42

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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#9

Post by halbritt »

That's precisely what I was looking for, thanks.
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PJMehaffey
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#10

Post by PJMehaffey »

Which size do you use on which bike?

GL1000?
GL1100?
GL1200?

5mm or 6mm?

Thanks

Patrick
Always ready to Ride!

1984 GL1200I 1978 CB750K (project) 1977 CB750A (project)


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CYBORG
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#11

Post by CYBORG »

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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#12

Post by buzzinhalfdoz »

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 ??
siebo
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syching

#13

Post by siebo »

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
1987 gl1200 interstate
gl1500 se
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RB
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#14

Post by RB »

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

#15

Post by gapl1953 »

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

My father use to say, "Anyone can fix it with the right tools"!
I say, "If it don't fit, get a bigger hammer"!
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