Fork rebuild

I originally posted this on yamahasupertenere.com, here is the linky: http://www.yamahasupertenere.com/index.php?topic=6550.0

So I figured, i’d share this with forum members.  My bike has 22xxxkm on it, and it was time to change the fork oil.

Below is a write up on how I went about it. You will need the yamaha book for this, and I highly recommend a spring compressor tool to make the job for one person easy. It’s an easy job, a bit messy mind. Keep an eye on all your parts, how things come apart etc..etc.. the yamaha book is very handy, and the cut away drawings are excellent for reference. BTW….usual BS disclaimer, this is for the home mechanic, if you break something, don’t blame me for it ::014::
Oil change on front forks. This is a write up for some additional info  to the yamaha manual.  Some of the points are bit convoluted for no apparent reason.  To make the job easy, I purchased a spring compressor kit from traxxion dynamics ($36 plus shipping on ebay), and a oil level c/w syringe from the local stealership for $40.

Secure the bike, and elevate the front end. You will need a 19mm alen key socket to remove the front wheel. Bottom pinch bolts are easiest to remove with a ratcheting wrench (10mm)

Once the forks are off, clean them in kerosene, to get all the crud off, do the bottom first. Also if you have fork skins, pull them onto the top of the fork (gold part) so they are out of the way, you will need to bottom the fork, when re-installing.

Prep the fork in a vice, at a slight angle, use a 14mm open end wrench to turn the pre-load all the way in, so the 24mm socket can sit properly on the top cap nut (pictured)also, cover the cap bolt with tap, to minimize the bastardizing effect on the soft material ::025:: Hold the top cap, and use the 14mm wrench to hold the nut on the dampner rod -unscrew the cap bolt, put it aside, as well as items 2 through 7.

Drain the oil out of the fork.  there’s two ways of doing the fork oil:

1: Leave the dampner rod in, and try to get out as much oil as possible by pumping it (easier, but will leave some old oil, crud and what have you in the dampner).  This is a bit easier, as you don’t have to faff around with the bottom bolt that holds the dampner in.

2: Remove the bottom bolt holding the dampner in, and take the entire fork apart.  You may need to double nut the dampner rod to keep in in place, but if the fork is held in the vice properly, the bottom bolt, comes out easy (impact gun certainly helps), or an assistant.  You can also use the nut out of the second fork to hold the dampner rod in place (pictured)

I will remove the dampner.  This will allow  a proper clean.  I dunk the all parts in kerosene, and I also pump kerosene through the dampner rod, that way all the old oil comes out. -once everything is cleaned, you are ready to re-assemble.

Ready for re-assembly.  re install bottom bolt holding dampner rod, put fork back in vice, upright. pour 200-300ml of oil, into the fork and work the dampner, to get all the air out.  Once you have drag on the dampner, the air should all be out.  measure the oil level, with the spring guide out, either out of a home made syringe and tube (cut to 150mm) or a level gauge (pictured). Once oil level is proper, install the spring, make sure your nut is sitting tight on top of the spacer (book says you need 12mm of thread showing, tight is pretty much there. to make life easier take the preload, and back it all the way out, this will give you room to thread the cap bolt on with no real issues.  Once the cap bolt is on snug, install the spring compressor. compress the spring and tighten the cap to the specified torque…tight plus a bit works here :) Install the back on the bike, following specs in the yamaha book.

Here’s the fork in the vice, secured, so I can undo the top cap

Fork Cap out
Fork compression tool (traxxion dynamics)
Yamaha says 150mm from the top, with the spring, the fork spring guide, and other bits and bobs out
UPDATE: MARCH 3rd 2013.
So it appears that I may of gotten my oil weights all wrong.  Yamaha 01 weight oil does not equal 10W oil.  It’s actually closer to 5w (manufacturer dependent)
here’s a couple of handy charts that one can go by.
I read somewhere that a high Viscosity index is a good thing (VI), as it copes better with temperature changes.
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