Firstly ive cut the yzf steering stem just above the yolk upper surface...then carefully cut with the hacksaw [fit the blade through the hole and reassemble]...through the stem down close to the alloy yolk..stop a little short..the wedge youve made will snap out easilly.
Then remove the stem section...there you go, a yzf lower yolk ready for the trx stem.
Now, cut and do the same to the trx lower yolk...seriosly..what are you going to do with the empty lower anyway, and being in two pieces, its twice the ammo for the neighbours cat ..
Eventually you will have the two hopefully correct pieces to be off to the mechanics bearing press, its a 2 minit job, so the cost shouldnt be too much.
End result is ready to go on the rex.....no fuss..the new tapered steering head bearings for the trx are the must have too.
The yzf tubes i have found sit flush to the top of the upper tripple to give the same height as the old system..you still have the speedo drive and will have the larger 320mm discs while your blue spots will fit given the lower trim out.
sweet as your nanna.
