Carb synch - off enough to worry?

Hi all,

Just checked the carb synch, and the vacuum levels are pretty consistent except for a difference on #4. Is this discrepancy enough to start fiddling around? I've never had good luck tuning carbs and the bike is running pretty decent, I'd rather not go down the rabbit hole.

Here's a vid:



Thanks!

What carbs do you have? If they are similar to the Mikuni VM24SS carbs on my bike they are extremely easy to synch. You simply remove the top cover and adjust the height of the slide using the screw on top until all gauges rear the same.

I can't tell how much the #4 carb vacuum differs from the others, but for the KZ650 all 4 carbs should be within 2 cm Hg of each other at idle - at which the vacuum reading should be between 19-24 cm Hg. You bike may differ some, so you should check the Kawasaki Service Manual for details.

BUT, before you make any changes here's a suggestion. No offense intended, but the gauges you are using are not the most accurate in the world. I know because at one time I had an identical set. SO, to check the validity of the gauge readings you should try this - hook the #4 gauge to #1 carb, #1 gauge to #2 carb, #2 gauge to #3 carb, and #3 gauge to #4 carb. If the gauges still show the #4 carb (that would now be gauge #3) to be the carb that is out of synch your gauges are probably in good shape. If, however, #4 carb now shows the same reading as #2 and #3 carbs and instead #1 carb (gauge #4) is out of synch, there is a problem with the #4 gauge as it is consistently reading low.

Ed

Hi Ed,

The carbs are BS34s. There's no absolute spec for vacuum in the FSM that I could find, just no more than 2 cmHg difference between cylinders.

Oops... :blink: I was looking at the outside scale and saw 1-3 sitting at "10", and #4 at "12", so it looked sorta OK... but upon further review, I was reading the wrong units on the outside scale of the gauge, which I just realized is INCHES of mercury, not mm.

So now, if I'm reading the gauges right, the inside scale is mmHg (the one I want), so 1-3 are showing approx 250 mmHg and #4 is at 300. So convert that to 25 cmHg and 30 cmHg respectively, and I guess that answers that question eh? But I will definitely swap the gauges around and make sure the relative values follow before I start making any changes, thanks for the tip on that!