Welcome to Netrider ... Connecting Riders!

Interested in talking motorbikes with a terrific community of riders?
Signup (it's quick and free) to join the discussions and access the full suite of tools and information that Netrider has to offer.

A few observations on the GPX250R

Discussion in 'Technical and Troubleshooting Torque' at netrider.net.au started by Admiral Thrawn, Feb 26, 2007.

  1. I've been cruising around sidestreets and carparks working on balance and noticed a few things.

    1. No-hands riding.

    Quite often the handlebars will start wobbling from side to side, slightly at first, then getting faster and faster and more severe until I have to take control of them again. Is this caused by the lack of a steering damper? Most of the time I'm going < 40 km/h on a flat, straight road. I noticed that if I lean back when cruising along with no hands this happens much less often.



    No-hands is made more difficult on the GPX because of the amount of engine braking so I try it in 6th.

    2. Angle of handlebars

    Looking down at the front of the bike when travelling straight, the handlebars appear to be turned very slightly to the right. I assume this is due to the camber of the road sloping down to the left?
     
     Top
  2. is your front wheel balanced? i experienced this w/my gpx a couple of months ago when doing a rossi impersonation leaving the pit garage (you know the stand on the peg, no hands, fix your tackle riding ;) ). my front tyre needed replacement at the time as well. your tyre wear will also suffer if your wheel is not well balanced, you might find one side is worn out more than the other.
     
     Top
  3. Sounds like what happened when I crashed my GPX and the forks twisted in the triple clamps
     
     Top
  4. Haha, it's certainly not the lack of a steering dampener. As the bike slows down it loses the gyroscopic forces (wheels spinning) which keep the bike steady and straight. Anything below (funnily enough) about 40km/h it will start to become unstable, it's the same on my VTR250. 80km/h is a nice speed for no hands riding, if only I had cruise control.
     
     Top
  5. I might take the bike in to the dealer just to make sure the front end it spot on.

    About half the times these wobbles don't occur, and I can roll along till just above walking pace until the bike starts to follow the camber of the road and the leaning gets a bit extreme. Eventually the steering gets out of whack and I have to concede defeat. :p

    As bonjoji mentioned, how does Rossi stand up at a really slow speed and adjust his leathers or wave to the crowd? If I tried that on the GPX as it is right now, half the time I'd have to sit down in a hurry to control the oscillations or it would fall over. Does the stiffer suspension and different geometry make a racing bike more stable doing such things? Perhaps there is just something wrong with the front. Definitely worth checking out! :)
     
     Top
  6. Maybe he puts it in neutral?
     
     Top
  7. Yup, that would make sense. Don't think it would affect my steering issue though. Will give it a try tomorrow. :wink:
     
     Top
  8. The gpx has a 16" front wheel, which makes it a bit more susceptible to instability.

    Still I'd be string lining the bike to make sure. It may be your rear wheel is out of alignment or your front axle isn't horizontal.
     
     Top