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synchronizing carbs

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sclafani
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synchronizing carbs

Post by sclafani »

I have a 1965 R50/2. I'm synchronizing carbs and have the Barrington publication which explains what to do. It would be helpful if there was a video (YouTube) available. I searched the web with no success for my year bike with the Bing carbs. Does anyone have something they can share that would make the effort easier?

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schrader7032
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Re: synchronizing carbs

Post by schrader7032 »

Probably not that much help, but it's basically all the same. Here's Matt Parkhouse talking about synching /5-on carbs:

https://www.youtube.com/watch?v=5bmJ0iYBYgQ

Also search this forum for EMPI. They are a set of vacuum devices which can be helpful for synching. Maybe somewhere in those discussions the general approach to synching /2 carbs will be discussed.
Kurt in S.A.
'78 R100/7 '69 R69S '52 R25/2
Fast. Neat. Average. Friendly. Good. Good.

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vechorik1373
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Re: synchronizing carbs

Post by vechorik1373 »

This is how it is done. You don't need a video.
First, you cannot sync the carbs unless you have checked for differential timing. If the engine has differential timing, (one cylinder is firing ahead or behind the other) you are simply wasting your time attempting to sync the carbs.
Do you know how to check for this common problem?

But, assuming you do NOT have any significant differential timing (the factory specified 3 degrees or less) The procedure is as follows.
You must have the idle air mix set correctly. Have a 9 mm wrench and a screwdriver that fits the slot of the air mix screw.
Fire the bike up, But FIRST, when it is running, check for a vacuum leak, by spraying carb cleaner where each carb meets the head. If you hear any speed change, it means you have a vacuum leak, and you must fix that, or you will not have a consistant good low idle and you will not be able to sync the carbs.
Remove one plug wire, (if the cyl that it is running on, quits, (and it will IF you have differential timing and it is the cylinder that has retarded timing which is why you must check and correct that problem) raise the slide just a little little, put the wire back on, fire it up and pull one plug wire. While it is running on one cylinder, loosen the jam nut of the idle air mix screw, a slowly try screwing it in or out, and use the air mix screw, to obtain the MAX rpm on the running cylinder at that slide stop position. When you find that position that gives the MAX rpm, if it is running a bit too fast, back out the slide stop screw a little, and slow it down to a low idle. Then you may find, (if it was way off) you might have to repeat adjusting the air mix again.

Repeat the entire procedure on the other cylinder. Then when you think you have the mix set, stand over the bike, and pull one plug wire for an instant, LISTENING to the speed, put that wire back on, and immediately pull the other plug wire.
If from listening, you detect that one side is running slightly faster, back out the slide stop screw a little, to slow it down, and repeat, the pull each wire/listen pull the other wire listen to the speed test. When they sound the same, NOW you have not only the mix correct, but you have both slides set to give the same rpm on each cylinder.

Next, make sure the front wheel is positioned dead straight ahead, and check to see if you have cable sheath slack on both sides. You should be able to pull each sheath up just a little, without the rpm coming up off idle. If you don't have any slack, use the cable adjuster to get some.

Finally, to sync the carbs, you break the jam nut on the cable adjuster loose on the LEFT carb, put your right hand on the throttle, (and have an assistant hold the left cable sheath in their fingers to prevent the sheath from twisting when you made your sync adjustment)
What you are going to do, is sync the left carb to the right one, by S-L-O-W-L-Y opening the throttle, to just above idle,and hold it there, while using your left hand to screw the cable adjuster on the left carb in, or out. When the engine is out of sync, and you hold open the throttle just off of idle, the engine will rock back and forth (left to right) and vibrate.
So, you screw the left adjuster in, or out, and you will either see the vibration get worse (which means your going the wrong way) or get better. Continue to turn the adjuster in the direction of improvement, until you find that "sweet" spot, where virtually ALL the vibration disappears. Then shut the throttle down, and tighten the jam nut on the cable adjuster.

Check it by opening the throttle again, very slowly, and if the RPM comes up with engine vibration, you have successfully synced your carbs! If it is not as perfect as it was before you tightened the jam nut, try this last procedure again.

That is the away I was taught to do it by a factory trained mechanic about 50 years ago when I had just started working in a BMW shop!
Vech
Technical Adviser, Former owner, Bench Mark Works
662 312 2838 cell 9 am to 4pm CST PLEASE!

sclafani
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Re: synchronizing carbs

Post by sclafani »

Mr.Vech…..Thank you AGAIN! for your knowledge. Very much appreciated. You have answered a number of my issues. This is my first BMW restoration and you and, other good folks on this site have help out considerably. If you're ever in the Southeast Florida area please look me up……cocktails are on me!

Steve S

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Re: synchronizing carbs

Post by xackley »

Oops, I think a slight typo at the end of Vech's excellent tutorial.
"Check it by opening the throttle again, very slowly, and if the RPM comes up with engine vibration, you have successfully synced your carbs!"

I think he meant Without Engine Vibration in that sentence.

On my r69 I do all the above after a complete carb cleaning. Then I take it out for a ride. After a thorough warm up, I loosen the left locker on the cable adjust and fine tune. Tiny twist. After 3 or 4 tries I find perfection. I do have modern cables I bought from Vech quite a few years ago. But my theory is there is a minute difference in stretch when actively riding.

Don
1958 R69, 1972 R75/5, 1980 XS650, 1982 GL1100, 2003 guzzi ev, 2017 guzzi V7!!!
All on the road, going no where in particular in the Finger Lakes of New York

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Re: synchronizing carbs

Post by 808Airhead »

Vech's way is the correct, time tested procedure, if one is methodic and lucky ,it can achieve a good/great result. I have tried by ear and eye to synch,and only after using the EMPI snails,did I realize it was not spot on, now I am a huge fan of the EMPI SNAILS/air flow meters, I use these to synchronize my Weber 44IDF carbs on my replica speedster,and use them to great effect on my 4 vintage BMW bikes. These take all the guesswork out of the equation,I use them to equalize the carbs,and when adjusting mixture you can visibly see as well as hear the fluctuation when adjusting mixture screw, to set it at the smoothest running, then you adjust idle speed screw to have each side with the snail needles in the same exact range,at that point your idle will be perfect,THEN you simply SLOWLY CRACK THE THROTTLE and you will see which carb is early or late and you can adjust the throttle cable to give you absolutely PERFECT matching throttle opening. This makes the machine turbine smooth and very easy to come off idle and start rolling,as well as eliminating any bucking/uneven running at light throttle. Over time you will have a cable stretch and it is a 5-15 minute job to remove air tubes and stick the snails on and adjust the cable slack to make it perfect once again. If you have OCD and ADD like most of us here, then you will LOVE the snails,you can get your timing and carbs right,it will run turbine smooth. These will have your carbs setup like an expert,without being one Have fun!
Last edited by 808Airhead on Sun Feb 05, 2023 4:13 am, edited 1 time in total.
Thomas M.
R69S - R60/2 - R67/2 - R51/3 - R69

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vechorik1373
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Re: synchronizing carbs

Post by vechorik1373 »

Don,

Your right, I made a typo error!
Vech
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662 312 2838 cell 9 am to 4pm CST PLEASE!

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skychs
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Re: synchronizing carbs

Post by skychs »

808Airhead wrote:
Fri Feb 03, 2023 6:21 pm
Vech's way is the time tested and if methodic and lucky can achieve a good/great result. I am a huge fan of the EMPI SNAILS/air flow meters, I use these to synchronize my Weber 44IDF carbs on my replica speedster,and use them to great effect on my 4 vintage BMW bikes. These take all the guesswork out of the equation,I use them to equalize the carbs,and when adjusting mixture you can visibly see as well as hear the fluctuation when adjusting mixture screw, to set it at the smoothest running, then you adjust idle speed screw to have each side with the snail needles in the same exact range,at that point your idle will be perfect,THEN you simply SLOWLY CRACK THE THROTTLE and you will see which carb is early or late and you can adjust the throttle cable to give you absolutely PERFECT matching throttle opening. This makes the machine turbine smooth and very easy to come off idle and start rolling,as well as eliminating any bucking/uneven running at light throttle. Over time you will have a cable stretch and it is a 5-15 minute job to remove air tubes and stick the snails on and adjust the cable slack to make it perfect once again. If you have OCD and ADD like most of us here, then you will LOVE the snails,you can get your timing and carbs right,it will run turbine smooth. These will have your carbs setup like an expert,without being one Have fun!
I agree. I bought two of the EMPI snails this year and it really made a difference. For the first time I can tune my own bikes.

I have printed out all of these procedures and will keep them in my Barrington book. Thanks for the information.
1966 R60/2, 1967 R69S, 1975 R90S, 2020 R1250GSA

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Re: synchronizing carbs

Post by 808Airhead »

Anone using the EMPI snails,do not twist throttle open quickly,it will break or ruin the meters. Ask me how I know :lol:
Thomas M.
R69S - R60/2 - R67/2 - R51/3 - R69

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