Carb Sync Observations

[BearOnt]

I bought myself a carb sync tool and put it to use today.
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.
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.
d) The warmer the engine gets the more frustrating this job gets.

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.

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

[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.

[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....

[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.

[heraldhamster]

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

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

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.

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.

[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

[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]

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

...james.

[halbritt]

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

[PJMehaffey]

Which size do you use on which bike?

GL1000?
GL1100?
GL1200?

5mm or 6mm?

Thanks

Patrick

[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.

[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.

[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.

[RB]

OOPS

[gapl1953]

I bought myself a carb sync tool and put it to use today.
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.
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.
d) The warmer the engine gets the more frustrating this job gets.

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.

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.