I need to realign my forks and front wheel

From Ninja250Wiki
Jump to: navigation, search

Whenever a bike is involved in any sort of accident (including bumping a curb, or hitting a large pothole) it can bend the fork tubes or twist them in the triple trees. Crashing falls into that criteria where something can get a little 'off', so it's best just to check and adjust. The forks may be tensioned and the wheel can be pointed in a direction other than dead ahead.

Bent forks

Bent forks fall into 2 categories:

  • A bend with a crease, where the tube is trash. There is no way to remove wrinkles from metal tubes while retaining their specific tolerances. You test for this by just wrapping your hand around the tube (above the dust seal and below the lower triple) and sliding it up and down. You can feel for the crease. It's usually on the back side (closest to the radiator), and just below the lower triple. FWIW, the bend can be Quite impressive in amplitude and still not contain any crease, and can thus be straightened.
  • Slight bends are harder to test for, but you can do so by pulling the fork from the bike, putting the chrome part of the tube on a flat surface with the leg hanging over the edge and rolling it (kinda like you would a pool cue). If the end wobbles, you have a bent fork. It can be straightened for not a whole lot of money. Anyone with a hydraulic press can straighten forks; it's not a complicated process. Between a motorcycle/auto shop and a true machine shop, the machine shop would be better able to complete the task. If there is a crease, however, the tube is complete trash.

A large number of people ride for thousands of miles with bent forks and never know it... but chronic leaking fork seals are one good clue (and a good reason to have them fixed).

Front end misalignment

To align the forks, you need to get the front wheel off the ground by any way other than pushing up on the bottom of the forks. This photo shows a proven and stable method. Other methods

Front wheel support.jpg

Make sure you use the centerstand. You don't want all the weight of the bike on the pipes. Leave the front wheel on and weigh down the rear end until the front tire's off the ground. Put something under the front tire (boards, old phone books, or something else that won't crush) just thick enough to touch the tire but not push it up.

Loosen up all four triple tree clamps and the front axle. Then wiggle the front wheel back and forth. This will 'reset' the forks and release any pent up tension. Then just make sure that the forks are still fully inserted (they didn't slip out any) and that the top triple trees are even on the fork tubes; if they're not, move things around until they are. Tighten the clamps back up, carefully, slowly, and evenly.

If nothing was bent, chances are good that it'll now be straight. This might help the 'feel' of the bike a little too, as you can get things back to neutral. This takes very little time and can provide huge benefits.

Front end alignment v2

The first thing you should do is figure out if the handlebars themselves are bent before you start messing with the alignment.

To realign your front end, you need to remove the front fairing, and then the handlebar risers from the triple clamps. Then do as follows:

  • Support the front of the bike so that the bike will not slide up or down when you start working.
  • Loosen the 4 triple clamp bolts that keep the forks held in their proper position.
  • Loosen the 4 bolts that hold the front fender to the forks.
  • Loosen the axleshaft bolt.
  • Slide the fork tubes up or down as needed, so that both are sticking out the same height from the upper triple clamp. When the heights are the same, tighten the 4 triple clamp bolts.
  • Twist and turn the lower fork legs until you can easily insert and remove the axleshaft through the wheel.
  • Tighten the front fender bolts and then the axleshaft.
  • Reinstall front fairing, and take the bike for a test ride. Everything should be good to go.

The glass test, for fine-tuning

Since you'll be in naked mode anyway...

Get a piece of FLAT, THICK glass appx. 1/4" x 4" x 8" or so. When you think you have things lined up, place the glass across the fork tube sliders (the shiny bits).

Lightly press on diagonally opposed corners of the glass, and see if the glass "rocks". If you hear or feel the glass moving, the fork tubes are not parallel and you'll need to keep tweaking until the glass lays perfectly flat, or nearly so.

This really, really makes a big difference, having them spot on. As the EX250 forks are certainly not the most up-to-date items, any tweak or twist in them leaves them easily vulnerable to "stiction". Basically, this doesn't allow the sliders to easily pass the fork seals and hampers smooth suspension operation.

Bent triple tree

"I can confirm that the lower triple is made of Swiss cheese and pot metal, and will twist and bend if you even look at it funny." – Jim Race

Another question sometimes seen when talking about alignment concerns a bent triple. There is NO simple/quick way to check this with any accuracy. It really needs to be removed from the bike and checked on a design specific flat-plate (one that can accommodate the lump of the lower steering stem). If you think you have this problem, it's best to remove the triple, quickly check it as best as possible, then mail it off to someone like Traxxion Dynamics or GMD Computrack for straightening.

NOTE: The following is not an acceptable alternate method except in dire conditions (--satire--)