'79 XS 1100 Cutting Out Occasionally

[rwp53]

Sometime when I cruise around 70MPH, the motor starts to cut out (apparently not getting gas). I turn petcocks to "prime position" for about 10 secs, then back to "on" . Bike runs fine then. Thought it may be vacuum prob. Drilled larger vent hole in gas cap, but still happens. Any ideas?

[ratbyk]

Cutting Out at Speed

First try replacing the vacuum hoses running to your petcocks. If they are leaking, tired, partially plugged there will not be enough vacuum available at high speed to hold the petcocks open all the way.
If that does not solve your problem then a petcock rebuild may be next.
Before you do either, try running at speed with the petcocks set to prime. If this solves your problem then the two previous suggestions hold true. If it still runs out of fuel at high speed on prime check for plugged fuel filters/screens, kinked fuel lines, plugged vent in fuel cap.
Ken/Sooke

[prometheus578]

same symptoms

Just fixed one that had a kinked vacuum line to the petcock.