vacuum advance chattering

[hyperballsmcgee]

in that case i'm at a loss here then. all i know is that the bike is not pleasant to ride the way it kicks and bucks at part throttle. it's tons of fun at full throttle but sometimes a man just wants to cruise.

[hamjam]

just as another thought , what rpm are we talking about ,mine never happy to be below 3000 and was most happy between 4500 and 5000 and scary at 7500
, mine was tuned well

[DiverRay]

The XS in a well tuned condition is happy from 1,500 to 8,500RPM. Stumbling and popping at part throttle is probably pickup coil wires, but could also be carbs.
Try riding with a friend who has an ir temp gun. Put up with the bucking for about 2 minutes, pull in the clutch and kill the engine, then stop and have him look at the pipes at the head. You should be able to see one or two pipes with lower readings. 1&4 or 2&3 is pickup coils or coils. Anything else is probably carbs. Dig in once you know what direction to go.

Ray, I edited this, you had 1-3 and 2-4, I'm sure it was just a brain fart! T.C.

[hyperballsmcgee]

i have checked, checked, and checked again for the pickup wire issue and i can't seem to find anything there. not with the hourglass method, and pulling the wires in any direction does not make the motor change while running. i'm at such a loss here i've considered just replacing all the pickup wires to see what happens. i think i will start there. it's a lot cheaper than buying new coils to "see what happens"

[skids]

so getting no resistance on primary wires and erratic open resistance in plug wires indicates that BOTH coils are bad? seems odd that they'd both be out

You should get 15 ohms on the leads to the spark plugs even if the coil is off the bike. Erratic open when taken at the same conditions might be due to the meter leads making intermittent contact.