question about bench synching

Hi all,
recently got my 82 xj650 on the road but hadn't gone through it thoroughly which I plan to do this weekend. It was running decent after only rebuilding the carbs and doing a bench synch, but then began idling too fast. I've pulled the carbs off because the intake boots are (I believe) one of the problems. I've done the bicycle inner tube trick and I'm about to put the carbs back on but then noticed something, and this is what my question is about. When I have the control knob turned all the way in to its last thread, my throttle valves are still only open about 1/8th of an inch. Is that normal? I would expect that you could open them more but I don't see an adjustment that changes the relationship between the linkage for the four throttle valves and the shaft that they are attached to. Or am I missing something?
Thanks again for all the sage advice. It's such a pleasure to be able to play around with these bikes and get advice from the gurus!
Scott

 

The way I start is by having the idle screw turned in about half the length of the threads. Then I adjust the #3 butterfly to shut only allowing a strip of 3x5 index card to slide under it. Then the next butterfly to adjust is #4, then #2 and the #1. When all butterflies are adjusted, you still have plenty of adjustment left on the idle screw once you start the vacuum sync and colortune.

hope this helps

 

Make sure your float levels are accurate before attempting any "running" tuning.

The only thing that moves the whole set is the big ("big" is relative) knob located between #2 and #3; it is #3's only adjustment point.

Your primary concern is if when backed all the way out, the butterflies all close nicely. Use a flashlight from behind the rack and ensure they all close. If you're truly patient, you can use the "flashlight trick" to ensure they're OPENING at exactly the same time.

 

Starting by setting the #-3 Carb snugly closed on the Feeler ( I use 3X5 Card strips ) is Key.

Match 4 to 3

Then do 1 and 2.

It is important to know that the #1 and #2 Carbs are "Married".

During Vacuum syncing, ... set 1 to 2.

Then, when 2 is matched to 3 and 4, ... #1 gets matched along with it.

 

I found that I had to re-seat two of my butter fly valves on their pivot shafts before they would close properly.

Then bench synched, I used 'card stock' also, but cut them all to 1/4" wide.