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The Coil Pick-Up Fix
David Hansen
A common point of failure on the XS Eleven is the wires that connect to the coil pick-up located under the left-hand side case-cover. These two thin wires are forced to flex as the vacuum-advance rotates the pick-up. As they wear, one or both coils will become erratic, causing random misfiring at various RPMs. The fix is relatively simple - new stronger wires are spliced in place of the old, thin wires.
Most XS Eleven's are old enough that this little operation has already been performed as the ubiquitous original design flaw showed up rather quickly. So check those wires and see if they've been spliced (if not, do it) and if the splicing job was done well (my current bike had a very poor splicing job done). And remember to check those wires if you start to encounter erratic missing, they may be the cause.
Update
Norm Willey
Leads for a multimeter make good replacements because they are meant to flex continuously. The replacement leads are quite cheap and can be picked up at RadioShed (Radio Shack) or any electronics shop. Stabilize the solder joint with electrical tape (bends less than heat-shrink) so the wire is forced to flex somewhere other than the connection. Easy fix!
See Ken Talbot's Pick-up Coil Wire Repair with pictures; also The Coil FAQ and New Wires in Old Coils tips.
David Hansen
A common point of failure on the XS Eleven is the wires that connect to the coil pick-up located under the left-hand side case-cover. These two thin wires are forced to flex as the vacuum-advance rotates the pick-up. As they wear, one or both coils will become erratic, causing random misfiring at various RPMs. The fix is relatively simple - new stronger wires are spliced in place of the old, thin wires.
Most XS Eleven's are old enough that this little operation has already been performed as the ubiquitous original design flaw showed up rather quickly. So check those wires and see if they've been spliced (if not, do it) and if the splicing job was done well (my current bike had a very poor splicing job done). And remember to check those wires if you start to encounter erratic missing, they may be the cause.
Update
Norm Willey
Leads for a multimeter make good replacements because they are meant to flex continuously. The replacement leads are quite cheap and can be picked up at RadioShed (Radio Shack) or any electronics shop. Stabilize the solder joint with electrical tape (bends less than heat-shrink) so the wire is forced to flex somewhere other than the connection. Easy fix!
See Ken Talbot's Pick-up Coil Wire Repair with pictures; also The Coil FAQ and New Wires in Old Coils tips.