Bike jerking wildly

jfrattarola

XS400 New Member
Messages
2
Reaction score
3
Points
3
Location
DC
Symptoms:
  • bike stalls at low speeds
  • takes forever to start after stalling
  • once accelerating, bike thrashes wildly, jumping between 0-6000 rpms, jerking like crazy (scary)
  • even at steady throttle, bike will start thrashing
Background:

This is a 1977 XS400 with about 12,000 miles on it. I've recently cleaned and adjusted the carbs per the guidelines on this site (5 times). Swapped in hot spark plugs because one side was still a little rich. Everything has been running great for weeks. Then over the course of a 20 minute ride it started getting worse and worse. The only thing I've done differently is I let it sit in the sun all morning (instead of my garage).

Things I checked:
  • air intake clamps are all tightened
  • vaccum on one carb boot plugged. the other leads to my petcock as expected.
  • spark plugs looked fine (mocha), though one was a little brown.
  • throttle cable seems fine
  • ran in prime on the way back (same problem)
  • gas is full
I'm going to yank the carbs and clean them first, but if these symptoms seem familiar to anyone, I'd love some feedback. Thanks!
 
Back
Top