Trouble syncing carbs

Using a carbtune pro (with YICS blocked using Chachal tool) and several times all 4 rods would just drop to the bottom, as though the vacuum completely went away even though the bike is still running. I could rev it and that would get the rods fluttering again, and they would continue for a while after it returned to idle. I don't see how anything could have pinched or interfered with any of the vacuum lines, and certainly not all 4 of them. I might have suspected an air leak, except that the problem hits all 4 cyls at the same time. So, I'm a bit baffled.

Anyone ever see this before, or have any ideas?

 

Are your valves in spec?

 

I've never watched mine while running since I've always had the air filter intake boots on when I tune and sync. I wouldn't think you would get a good sync without everything hooked up. But it is my understanding that the pistons don't move very much, and I suspect they might well be all the way down at idle. If it runs well I wouldn't worry about it. However, there are some folks on here that can cover you up with good information.

 

The valves are in spec. That's one thing I'm confident I did right, getting them in spec before I even touched the carbs.

The rods I was referring to are inside the carbtune. It uses steel rods as indicators instead of mercury or another liquid. So the symptom is the carbtune suddenly drops to zero on all 4 carbs, I can rev it and they start showing readings again, continues to show readings while and after the bike returns to idle, then after maybe 30 seconds they will all suddenly drop to zero as if the engine stalled, even though it's still idling.

 

do they drop slowly or like Joseph Kittinger jumping out of a ballon?

 

Sounds like a leak in the CarbTune somewhere.

Try turning it upside down.

 

That's a good idea. It hadn't occurred to me that the carb tune itself could be leaking but it makes sense. I'm gonna hook it up again and see if I can discover a leak in it.

 

If you don't find a leak, just hang it upside down like Fitz mentioned - not sure how much vacuum these bikes put out but under a certain level, the carbtune manual says to hang it upside down.