Carb Sync Observations

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britman
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Re: Carb Sync Observations

Post #16 by britman » Sun Jul 18, 2010 6:21 pm

gapl1953 wrote:
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

I just spent two hours i think none are in the same spot on the gauges . well one bike was but didnt mess with it as first time with gauges but 45 minutes come on
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Re: Carb Sync Observations

Post #17 by gapl1953 » Sun Jul 18, 2010 11:55 pm

britman wrote:
gapl1953 wrote:
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 experiencing 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

I just spent two hours i think none are in the same spot on the gauges . well one bike was but didn't mess with it as first time with gauges but 45 minutes come on



Well I went back out in the morning and discovered I made a boo boo :oops: putting on the right belt. I corrected that and it took me 20 min and had them all sync-ed to the same number. I have done a good number of multi carb sync jobs which helps. You need to anticipate how much a turn of he screwdriver is going to affect the remaining carbs, whether there is one or eight additional carbs.
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Re: Carb Sync Observations

Post #18 by mortiki » Mon Aug 09, 2010 1:07 am

Here is another tip I hope helps someone. Best to use one gauge and record progress but if using multiple gauges pick one for base and record #3 then put #1 gauge on #3 and see what reading is. Record the difference and mark #1 gauge accordingly. Hook up #2 gauge to #3 and record difference and mark,again without any changes, and then #4 gauge on #3 and record difference and mark. Now all your gauges are calibrated to sync a lot closer. This method only works on the 4 gauge dial setup so if your using a single gauge or tubes it may not work.
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Re: Carb Sync Observations

Post #19 by Sandy » Mon Aug 09, 2010 7:36 am

I calibrate each vacuum gauge to one common cylinder before hooking up the gauges to the individual cylinders.
Your vacuum gauges should have a little adjustment screw on the face of the gauge that will reposition the gauge face under the needle. just unscrew the gauge face plate.
I have also made a little 4 gauge header out of aquarium 'T's" and "90's" so all 4 gauges can be adjusted to one vacuum source.
Seems to work ok.

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Re: Carb Sync Observations

Post #20 by bluewing » Sat Aug 10, 2013 10:31 pm

I had a motion pro with the blue liquid but I had problems with air bubbles and loosing the liquid, also having to calibrate it every time I used it.
I ended up with a Morgan Carbtune and I find it to work very well, every time. It has metal bars that show the vacuum level instead of liquid or mercury and there is very little pulsing, it stays very steady.
Here is there website.
http://www.carbtune.com/
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Re: Carb Sync Observations

Post #21 by bartmead » Sat Aug 24, 2013 11:34 am

I too recently synched after a carb rebuild. I have the dial gauges and it took about 45 minutes to get it "close". If there had been a camera on me I would love to watch myself at super fast playback. I must have gone around the bike 500 times. I had my shop door open but I bet an air quality test by osha or the epa would have shown the air pretty deadly. I survived and only lost a few IQ points. My IQ is still high enough to use the internet.(thats not saying much)
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Re: Carb Sync Observations

Post #22 by Atticka » Thu Nov 07, 2013 6:11 pm

Some of the newer model carb sync tools have a restriction in the hose to stop the needle from bouncing around so much, others have a valve that you can use to control the bounce of the needed.

I use a Morgan CarbTune.

On the GL1100 Cylinder #3 is the reference carb and has no adjustment screw, all other carbs will be synced to this one.

The #4 carb actually controls the entire left side, so adjusting #4 will move #2 along with it.

So...
Adjust #1 to #3
Adjust #2 to #4
Then Adjust #4 to #3 (which will bring along #2 with it).

Hopefuly this helps!
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Re: Carb Sync Observations

Post #23 by gregforesi » Thu Nov 07, 2013 10:08 pm

A true guru can sync these bikes with nothing but a screwdriver and an ear to the primary chain. When it quits rattling you've nailed it.
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Re: Carb Sync Observations

Post #24 by ericheath » Fri Nov 08, 2013 12:00 am

I read of a guy who holds a piece of tubing from each of two carbs in each ear. He said he could tell the difference in pitch from each ear. Now that's tuning.
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Re: Carb Sync Observations

Post #25 by sunnbobb » Fri Nov 08, 2013 3:19 am

A true guru can sync these bikes with nothing but a screwdriver and an ear to the primary chain.


I watch the ears on my cat, when they quit twitching, she is in perfect synch. :)
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Re: Carb Sync Observations

Post #26 by AussieGold » Fri Nov 08, 2013 3:51 am

sunnbobb wrote:
A true guru can sync these bikes with nothing but a screwdriver and an ear to the primary chain.


I watch the ears on my cat, when they quit twitching, she is in perfect synch. :)


i also like to keep the cat in perfect synch........ lolol
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Re: Carb Sync Observations

Post #27 by fish » Fri Nov 08, 2013 7:59 pm

The Vincent spends so little time at idle I did the bench idle synch and let it go at that.
I also idle him at 1100 RPM it is smoother with a fast idle.
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Re: Carb Sync Observations

Post #28 by Paul Narramore » Tue Mar 22, 2016 7:31 am

I pleased to read others also have problems with carb synchronising. A friend loaned me a set of four gauges, each with a small valve beneath each gauges which I presumed was an anti-flutter valve. They aren't. What seems to happen is that I turn an adjusting screw at which point, the needle stays still, then a tweek of the valve and the needle moves to a new reading. So each adjust has to be followed by a repeated tweeking of these valves.

I have carb 2 and 4 to match No3 (A reading of 4 on the gauges).

No1 though is a pain. No amount of turning of adjusting screw makes a bit of difference and the needle fails to move up or down (A reading of 1.5 on the gauge). Also the revs go sky high every now and again yet pressing down on the screw or it's back plate calms the revs.

In theory I'd like to detach all of the throttle cables from the carbs then the tightness or whatever wouldn't effect the carbs, then once the carbs are adjusted, re-attach the throttle cables.

So far, with three of the carbs reading the same, the bike is misfiring, popping and banging. Rubber tube no2 has an inch or two missing from the end where it goes onto the brass tube, and the popping and banging ejects this again and again.
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Re: Carb Sync Observations

Post #29 by gltriker » Tue Mar 22, 2016 8:23 am

Paul Narramore wrote:I pleased to read others also have problems with carb synchronising. A friend loaned me a set of four gauges, each with a small valve beneath each gauges which I presumed was an anti-flutter valve. They aren't. What seems to happen is that I turn an adjusting screw at which point, the needle stays still, then a tweek of the valve and the needle moves to a new reading. So each adjust has to be followed by a repeated tweeking of these valves.

I have carb 2 and 4 to match No3 (A reading of 4 on the gauges).

No1 though is a pain. No amount of turning of adjusting screw makes a bit of difference and the needle fails to move up or down (A reading of 1.5 on the gauge).
Also the revs go sky high every now and again yet pressing down on the screw or it's back plate calms the revs.

In theory I'd like to detach all of the throttle cables from the carbs then the tightness or whatever wouldn't effect the carbs, then once the carbs are adjusted, re-attach the throttle cables.

So far, with three of the carbs reading the same, the bike is misfiring, popping and banging. Rubber tube no2 has an inch or two missing from the end where it goes onto the brass tube, and the popping and banging ejects this again and again.


What's the probability that the oring that seals the #1 carburetor's manifold, to the intake port on the cylinder head, is sufficiently damaged causing an air leak great enough to cause its specific vacuum gauge to be unresponsive to synchronizer screw adjustments?

edit: I reread the complaint again and noted you are tweeking the small valve beneath the gauges quite a lot. A reading of 1.5 never changes on #1. Have you tried switching two adjacent gauges' hookups and observe if that complaint follows the switch?
Maybe the tip of the needle in the small valve is stuck or broken off.
I noted on my 4 vacuum gauge set that if I shut a needle valve completely while the engine is idling, its specific gauge will hold that vacuum reading until the needle valve is opened again.
Last edited by gltriker on Tue Mar 22, 2016 8:54 am, edited 2 times in total.
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Re: Carb Sync Observations

Post #30 by ericheath » Tue Mar 22, 2016 8:39 am

If number three is open too far to begin with you'll chase your tail all day. Everything is ultimately set to match #3's vacuum. It cannot be adjusted. If it's high, you'll adjust #1 too high. Then you'll do 2 to 4 and they may be correct, but when you sync 1-3 to 2-4 they'll all be too high. Pull the elbows and bench synch them as close to shut as you can, then warm it up and sync it. You may have to turn the idle set screw in to warm it up.
Whatever I suggest here should be given ample time for a moderator to delicately correct. I apologize in advance.
77 WING, 1200 engine with 77 heads, cams, gl1100 foot pegs, Magna V65 front end, 764A carbs, [-gone Suzuki M109 monoshock--, replaced with gl1100 shocks] gl 1200 swing arm, gl1500 final drive, wheel and rear brakes Valkyrie seat, Meanstreak tank, Sportster pipes, Power Arc ignition off crank.
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