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Synchronizing Carbs

  • Thread starter Thread starter Anonymous
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Anonymous

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Is it possible to synchronize carbs without a synchronizer? I just got done rebuilding my carbs on a 1982 GS850GL and it is now idling like it should and runs pretty good, but you can hear that it isn't happy and is sluggish on acceleration. I do have a brand new K&N filter set up also.
Thanks for any help!
 
you could buy 4 vacume gauges and go to a bike shop and buy 4 brass fitting for the carbs so you can hook hose up to the fittings and the vac gauges. that should work, it may be a little cheaper then a mercury stix gauge, depending on how cheap you can get the vac gauges.

ryan
 
i am suprised there are not 40 posts to this question by now.
Is acceleration and sluggish through all ranges?
What did you set the adjustable fuel/air metering scres to? You can turn them each out to richen mixture a bit. Do you have CV carburetors?

Yes, you can sync carbs mechanicly and get VERY close. With the engine off. I set the throttle fixed so the but end of a NEW 3/16 drill bit passes snuggle between the carb inlet bore and the throttle plate. I then adjust each respective throttle plate to have the same "feel" as the drill bit slides past each respective carb bore and throttle plate. Back of the throttle before attempting to start.
 
Get a set of guages.

Get a set of guages.

Get a set of guages. The vacume type, and the mercury type are both cheap. Less than $50.00 in Den Kirk. I set mine manually first by sliding a bare piece of wire under the butterfly valve. After I put them back on the bike I found that synchronizing with the guages is the only way to get it right.
 
Get the mercury sticks they are easier to use. Just remember DON"T rev the motor up, Have you rejetted the carbs for the K&N filters?? that could be the big part of your problem
 
SqDancerLynn1 said:
Get the mercury sticks they are easier to use. Just remember DON"T rev the motor up, Have you rejetted the carbs for the K&N filters?? that could be the big part of your problem
Click to expand...

DITTO
 
The K&N filter was the one that goes inside the stock box, not the pods. DO I still need to rejet? The K&N website says no performance mods needed for the filter I got.
 
Re: Synchronizing Carbs

Not, not to any useful degree. I have set slide heights precisely and then checked vecuum levels with guages, Setting slide heights doesnt work accurately enough to be worth the time. The problem is due to machining differences and intake surface conditions, the slides will not all be in exactly the same position when vacuum levels are matched.

Earl


markstine said:
Is it possible to synchronize carbs without a synchronizer?
Click to expand...
 
Synching the carbs makes the most noticeable difference down low as that is when the slides are down. A bike can run like a dog, and with only a synch it is transformed, no rejetting.
 
Mechanical wear of carb linkages, carb components, change in engine condition between cylinders, slightly clogged jets etc. It may take a long time to notice any real change.
 
Did you mess with the synchronization screws during the rebuild? If not, then the sych'ing is probably not much different than it was before. No matter, at wide open throttle the synch'ing doesn't matter much anyhow. When I first went to a K&N, I had a similar problem to yours. It felt like I had stuffed rags into each carb it was choked so much when revved. It was due entirely to over-oiling the filter.
 
HOw do you know you have over oiled your air filter? I know gas has leaked into my air case, does that mean I should take it out and reclean it then reoil it, it hasn't gone 300 miles since I put it in.
 
Don't apply much oil at all.

As for the type of vacuum guages - dial vs. mercury - the mercury are self calibrating. This means that they do not requre any calibration - ever. The dial type, due to manufacturing tolerances are not all the same. They need to be calibrated. I would go with the mercury type and be careful not to snap the throttle open.
 
What Swanny said. Twice. A little bit of filter oil goes a long way. Too much and air doesn't flow through too well. How much is too much? Hard to say. Just put a very light coating on the filter and it will wick around and cover all the pleats.

Not to put too fine a point on it, it's snapping the throttle shut after snapping the throttle open that sucks out the mercury.
 
Not to put too fine a point on it, it's snapping the throttle shut after snapping the throttle open that sucks out the mercury.
Click to expand...
Correctomundo - my mistake.
 
If you're really ambitious, I'd do a valve adjustment prior to the carb sync because if you do end up doing a valve adjustment at some point, you'll want to resynch the carbs. I personaly like the dial guages simply because I'm not fond of mercury but if you've got money to spend, there's always the carbtune guages. The dial guages can be easily calibrated by using all four on one carb and adjusting them accordingly.
 
I have a mercury guage, but the book (Haynes) says the two outer cyclinders should be higher, but what should they be set at and how much higher should the out ones be? Does any one know what the Fuel screw should be set at? 1982 GS850L...
 
Bump.

So what is the deal with the different vacuum heights suggested for the 1980-1982 models?
 
The Clymer books show setting the outer cylinders (1 & 4) to a slightly higher vacuum level than 2 & 3. A higher vacuum means a higher intake velocity.
(volume remains unchanged) An example of that would be idle. You are increasing vacuum, but the engine is running at the same rpm, so its volume requirement is a constant. Increasing vacuum increases venturi effect and consequently fuel draw. Therefore, increasing vacuum, richens the mixture.
Aluminum conducts heat better than air. The 2 and 3 cylinders are surrounded by aluminum while 1 and 4 are open to air on one side. 2 and 3 will run cooler than 1 and 4. So you would want to set up 1 and 4 a little richer than 2 and 3 to get an even power impulse on all four cylinders.
I have found in practice, that I cannot tell any difference in performance or the color of the plug burn by doing this, so I no longer bother. If you do, the difference to set is 1 cm hg.

Earl


knelson said:
Bump.

So what is the deal with the different vacuum heights suggested for the 1980-1982 models?
Click to expand...
 
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