hello to all
i have a 97 cbr 600 f3 i'm having a problem trying to see a vacuum reading to sync my carbs. when i have the gauge hookup the needle is not steady
is like if you take your index finger and move it up and down very fast movement i check the spark plugs they are brown in color i even try using a one way valve=restrictor inline with vacuum line it help a little but still bouncy
bike runs fine strong except if i'm at a light that is long rpm fluctuate from 1500 to 1200

 

A one way valve may just not be enough to dampen the surge. You could try using regular valves that you can restrict the flow more with. Probably the only way it's gonna work.
I know the restrictors on many gauges are really small.

 

Its hard to get them perfect. The best thing to do is take the highest reading of each gauge and use that as the number the vaccum is reaching. such as, if its boucing between 12-15, think of that one as 15. then if the next one is bouncing from 10-13, bring it up until the highest number is also 15. It doesnt really matter what it drops too, as the highest number is how much vaccum is actually being pulled. But, as rpms vary, so does the vaccum. Once you get the rpms more stable, the vaccum readings will also become more stable.

Are you using actual dial type gauges? Cheap ones are not very accurate. A problem can also lye with good ones as they can be out of sync themselves.

I've had the best luck with tube type syncronizers.

 

do i need to sync my carbs if i installed a jet kit? 99f4

 

If you pulled the carbs to do it, you should.