Syncing carbs issue - stalling or pulling too much

Hi all :]

1980 kz440 LTD A.
So I decided to check how my carbs were doing as part of my to-do list. I've already checked valve clearances, new plugs and wires, checked the idle adjustment, syncing was next after cleaning the carbs about a year ago...

I'm doing the method where you have two bottles filled with fluid, and each one connects to the vacuum ports. The instrument is out of my price range (for now, unless need be)
So...I started the bike and immediately one of the bottles collapsed from the pressure, it was getting pulled very hard and I stopped the engine.

After messing around with the sync adjuster, there is no middle ground!
Either one of the bottles gets sucked so much OR the fluid is finally stable, still rising though in one, but the bike stalls.

The method seems very straightforward, adjust until the levels are equal, but I cannot get the pressure to stay relatively constant no matter where the adjuster is.
I tried its full range!

Any ideas on what else could be going on?

Thanks.

Did you bench sync them first?
Steve

Yes, apologies, forgot to mention that.

Do you have a destructor in each line that hooks to he carbs? If so, they may not be restrictive enough.

After researching I could not find out what this 'destructor' is...but what I can say is that there is nothing in the lines I have connected from the vacuum ports to the bottle!

Pretty sure he means a restrictor. A plug in the vacuum line with a hole in it in other words.

One alternate method to sync involves setting the idle up to 2500 or so and removing one plug cap at a time and noting what speed the engine idles at. It will drop to 1000 rpm or so. Anyway, set both sides so they idle at the same rpm when running individually. I think this is an old BMW twin sync method.

Yes, restrictor. I should have checked more closely before posting. They need be no more complicated than an old carb jet, or a plastic plug with a really tiny hole drilled through them.

What "fluid" are you using?
Homemade manometers can be anywhere from very good to totally useless. The restrictors are there to isolate the intake tract from the manometer such that the manometer can still make a reading but won't affect the reading. Without it, the manometer becomes part of the intake tract volume and affects the reading.

Do you have a link, or photos of what you are using?

newkzrider18 wrote: After researching I could not find out what this 'destructor' is...but what I can say is that there is nothing in the lines I have connected from the vacuum ports to the bottle!

Bottle? You really should use a proper tool for syncing carbs. There are a couple types out there including mercury stick types and gauges, but using a "bottle" sure sounds like a home made solution, and I cannot imagine that it could be very accurate. Here's what I use. Ed

This spring I picked up a Carbtune sync tool. Most of the ones online are being sold privately and are more expensive than from the company new.

carbtune.myshopify.com/

Make sure you use the restrictors as mentioned above. I first got an "affordable" gauge style balancer from amazon and broke two of the gauges because first my carbs were way out of synch and second I didn't use the restrictors. Instructions- should've read them.