Tonight in the garage

I was mostly trying to figure out exactly why the YZ's forks are so
stiff. It's always suffered from a bit of stiction, though it was
alleviated a bit when I had them rebuilt.

However, since I cartwheeled it last year it's got a whole lot worse.

It all *looks* straight-ish, but improves if I slacken off the
steering nut and the top yoke pinch bolts. Do them up, particularly
the RHS ones, and the stiction reappears.

Tomorrow I will mostly be trying to figure out whether it's the fork
tubes or the yoke itself that's bent.

I see many more bits on the garage floor...

 

Incorrect location of the front wheel spindle in the fork leg at the
non-threaded end can cause this. Check that the forks are not being
'squeezed together' when you tighten the spindle nut.

JB

 

wheel spacers in wrong or twisted bottom yoke.

 

Pip Luscher says...

"I see dead bikes"

 

A good trick for checking the stanchions are lined up straight in the yokes
is to lay a piece of plate glass flat across them. It should, in an
anti-Blaney-esque stylee, not rock.

 

It was somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember "platypus"

Surely, these days, a whizzy laser tool could be found to do that? Plate
glass just seems so... low tech.

We'll be using string and planks to align wheels next.

 

You're going to shine a laser on your nice, shiny stanchion?

Mmm. Cheap, too. Use an old bit of mirror.

Plenty of planks round here. Although I'd use a collapsible aluminium
ladder instead.

 

Raise the front of the bike off the ground, loosen axle and mudguard
then loosen the pinch bolts on one fork. Rotate the fork in the yoke, if
the bottom of the fork leg moves in and out... it's bent. Do the same
with the other leg, first remembering to tighten up the yoke pinch bolts
of the one you just loosened.

 

Good idea about turning the tubes & sliders: runout was no more than
about half a mm, measured at the bottom of the fork sliders (these are
USD forks).

At present it's got the wheel off, spindle loose, spindle pinch bolts
loose, dampers disconnected.

So I tightened it all back up (not the dampers), albeit without
checking the torques: no problem. Retightened the wheel spindle (wheel
still off) and its pinch bolts: no problem.

Retightened the stem nut fairly tight: no problem.

Slackened the pinch bolts off, turned the fork tubes back to their
original orientation, retightened: very slight stiction but nothing
like before.

I've been through this all a few times in the past with nothing to
show for it. It appears to have magically fixed itself

I is sore confused.

 

The spindle on the YZ isn't like a bolt with a head: it screws into
the LH leg and is clamped in the RH leg, so the spacers only serve to
to locate the wheel itself; they have no effect on the fork width.

 

Maybe it was the mud guard that was holding the fork legs apart
slightly... This is why I always do the mud guard up last[1]. Who knows,
maybe something was twisted and you sorted it by loosening / doing up
again.

[1]Unlike the bike shop that rebuilt the front end on my Bandit with a
4mm gap between the spacer and the fork leg, due to them doing the mud
guard up first... duh..

 

Uh, a YZ is a motocrosser; the mudguard is mounted on the bottom
yoke.

 

Right you are, I missed that small point.