BMW motorcycle telescopic fork alignment procedure, Randy Glass, page 9

9 – In The Meantime

      While you have everything apart and are waiting for the adjustment in the previous section to take it’s good time to get some of the other work done.  Now is the time to replace the fork seals and possibly to even think about getting the dampers rebuilt if it is necessary.

      Now is the time to examine the “Upper Fork Bracket” (the top triple tree).  This is relatively soft and it is possible that over the years it has become warped or bent from improper adjustment procedures and other forms of abuse.  Use a straightedge and check it on the top face and bottom face on its long axis for flatness.  The stock plate is easily bent back to flat using a bench vise- but BE CAREFUL! It is a lot softer and more easily bent than you may think.  If you have one end of it locked in a vise, one good pull will be all it will take to create an angle bracket good for mounting shelves to the wall and not much more than that.


Another thing to check at this time is the fit of the axle to the fork legs.  It is important that the axle move freely through the openings where it gets clamped in the axle, otherwise when you tighten the axle it will put lateral forces on the fork legs, pulling them towards each other, and this throw them out of alignment.

First, check the axle itself.  Clean it up, removing any burrs as well as the raised edges of any dings that might interfere with it’s surface flatness and slowly roll it on the glass plate to be sure it isn’t bent.  Being so short it is difficult to see if it is bent or not, so try using a .001″ or .002″ feeler gauge at various points under the axle as it is rolled on the glass plate.  Any deviance should prompt further examination or replacement.  A slightly bent axle can cause all sorts of alignment problems.

Now examine the “removal opening” in the axle shown as point “B” in this photo.  Remove any burrs there so that pulling the axle through the fork leg won’t scar the softer alloy.  Once that area is cleaned up, and with the pinch bolts loose as shown here, the large end of the axle should be easily pulled through the right legs’ opening.  Now, try to push the smaller end of the axle through its opening on the left fork leg.  I found that the end of the opening in the leg at point “A” above (the outboard side of the hole) had been made smaller by the years of tightening of the nut and pressure from the washer.  It had mushroomed the alloy just enough to not allow the axle to slide through.  I used a round file to slowly and carefully chamfer the edge to make that edge opening the same size as the rest of the hole.  WORK CAREFULLY!  Don’t muck up the rest of the surface and do not remove any more material than absolutely necessary!  Remove a small amount of material and then check the fit, then repeat the filing only if necessary.  You can always take a bit more off, but you can’t put it back!  Once done, with the axle inserted into both legs, it should be able to slide all the way through from one side to the other, only being stopped by the large end of the axle hitting the smaller opening of the opposite leg.  In actual usage (i.e. riding) this is not as important as it will be to test the alignment as we go along and in the future to verify that things are still lined up.

      Also take a look at the damper rods.  If someone has been in there previously, they may have clamped the damper rods in a vise without using some protection.  Look for burrs or gouges on the rods.  If necessary, clean them up with a fine sharpening stone or other suitable abrasive system.  When done, be sure to use some solvent on a rag to remove any metal filings or stray bits of abrasive.  It is critical to be sanitary when working on forks.

Previous Page                                                                                         Next page