flopping tach syndrome

[clarence]

I know this has been covered quite a bit before regarding the cutting out of one cylinder and the tach flopping around or stopping working. my rev limiter wire is cut, but what is the consensus on the most likely cause of this? I am thinking the pickup coils. would that be the best place to start troubleshooting?
cheers.

[Walt_M.]

You didn't say this exactly but is your tach needle jumping from actual rpm to zero and back? If so, it is probably a bad connection between it and the TCI box. You will need an electrical diagram to find which ones to check.

[Lucky]

if the bike is running good, but the tach is jumping:
check the grey wire between the tach & rear cyl, for continity & ground point in the tach for continuity to ground, check for dirty/loose connections
--repair connection if poor continuity or replace tach if connections are good.

if the bike is running badly:
check/swap the TCI (check for moisture,broken solder trace), check TCI plug for loose/dirty connections, check continuity grey wire between TCI to rear coil & tach. test coil.
--repair connection/wire if poor continuity, replace coil, tach or TCI

--Lucky

[Lucky]

wiring diagram here: http://www.xz550.com/wiring.html
note that the 'green' wire from the tach is really grey, (shown correctly after the connector)

[clarence]

thanks Lucky, I will try those things. I am glad the pickup coils are less likely to be a problem.

[QBS]

First thing to do is simple and cheap.  Clean your spark coil 12v connections.  The tach gets its signal from one of them.

[clarence]

SUCCESS  :) I pulled the tci unit apart and I couldn't believe it. virtually all the solder joints had dry cracked round circles in them . I resoldered them all, put it back and went for a 40 km ride and not a glitch. usually I could only go a max of 5 km's before it would start playing up.

[Lucky]

check/swap the TCI (check for moisture,broken solder trace),

Another Vision Gremlin Slain! Hooya!
if they were all that bad, it would be a wise idea to keep your eyes open for a spare.
Glad you got it tracked down quickly, now enjoy the ride!
--Lucky

[clarence]

I cannot believe how it could have run at all the condition it was in. I imagine as the components were heating up inside the tci unit, the expansion caused some of the bad joints to completely go open circuit.
I will look around for a spare unit.
thanks again.

[Lead_Deficiency]

Nice find !!!
My tach's been doing the same thing, i did all the wires this winter, but never took the TDI apart.