HOW TO, FORK OIL SEALS
HOW TO, FORK OIL SEALS
Nearly every time I look through e-bay at potential wrecks to restore after I have read the
description of how good or bad it is there is usually a little rider of “fork seals weep, I have a set,
but haven’t had time to fit them”…. which invariably means “I don’t know how to” !
The Tools you will need
In most cases the same bike has the front fender mounted backwards (WHY?) or if it’s a S Miller
one, then the stay is mounted the wrong way…. yes, the longer bit goes forward to allow the
cable room to go to the anchor bracket, and every now and then I see them with the fork legs
fitted in the wrong side to boot! If that’s the case you can guarantee the chain guard has gone
and it’s fitted with knobbly tires and a 14 tooth engine sprocket. I digress, back to fork oil seals…….
Let’s deal with a bog standard Yam from the mid 70’s. Dismantle with care! First drain off the oil
in the legs, The drain plug is on the side on the 74 and on the rear of ALL the later models.
A TY250A leg with drain on the side
Do NOT forget that little washer!
Remove the screw and the fiber gasket, apply the front brake and gently compress the forks to
see if there is any oil left…… BEWARE the oil can shoot out a long way!!! Remove, brake cable
from wheel, then the front wheel, fender (mudguard) complete with brace, and the brake anchor
arm. Now check the crown nuts, on the 175’s they should be proud of the top yoke and are easily
undone with a standard socket. All we need to know is that it will undo at this stage, on the
250’s the nut is recessed so you may have to make your own tool to remove these. Worst case
scenario buy a bolt and two nuts. Put the bolt head in the recess tighten up the two nuts against
each other then use a wrench to undo a couple of turns. Most of these nuts I see have had the
proverbial beaten out of them but just recently there is a company making these nuts to fit the
250 legs with a conventional nut on top. Check them out on e-bay.
Standard ABUSE of the crown Nut
Undo the allen bolts and remove the fork legs. Without damaging the alloy or the rubber, insert
a small bladed device under the “boot” and slide off, or you can wait until you have the leg apart
when you can compress the rubber with your fingers and it will pop off.
The Blunt Penknife Technique
This is now where it can get tricky! Seperating the top and bottom, again an allen bolt in the
bottom of the leg, and to undo it often needs a sharp crack or it will just rotate and never come
undone. If it won’t undo easily then you will need to see your friendly shade tree mechanic who
has a hammer drill, or the air compressor, or both. When the legs are in two pieces, and the boot
removed have a look at the gunge in the leg? Nearly forgot, when you have that allen bolt out
make sure you have the washer! Back to the gunge/water whatever, flush this out, it wasn’t
meant to be there and won’t help the fork action.
Use a Ring Spanner for extra leverage, and a rapid knock
Squeezing the “Boot” after parting the leg
Using an old blunt penknife or similar you will see in the top of the leg there is a wire over a
washer on the Yam system, others use circlips and in some cases nothing but today we have a
wire in a groove. Keeping the palm of your hand over the top of the leg prise out the clip from it’s
detent and catch it before it pings off round the workshop! Usually it will be rusty so a light bit of
emery work to make it fit easily may be needed. Next the seal, and here I use the “tire spoon”
as it has a perfect radius to exert enough pressure to lift the seal without damaging the alloy of
the fork leg. DON’T use a screwdriver for this or it may end in tears!
Blunt Penknife again lifting the spring clip, note my finger is covering the “escape”
The Tire Spoon has just the right Radius
Up she Comes!
Seal out, but keep it for now, and clean out the top of the leg and the retaining groove. Press in
the new seal and then put the old one on top and tap down with the rubber hammer until it’s
located below the retaining clip’s groove. Or use a special tool that fits in the seal and tap in until
you get to the right depth. Having cleaned the clip reverse the take out procedure and push
down into the groove keeping most of it covered or you will spend hours on your hands and
knees playing “hawkeye” !!
Using the “old” over the “new” technique
A simple machined tool to fit in the seal, this one is for a 175 but you get the idea
Having cleaned the top portion time to mate the two again. Hold the top portion upright and
slide the lower leg down onto it and this should prevent the end cap falling off. Do up the allen
bolt (with washer) and also put back the drain plug with it’s washer. Finally slide the boot back
on and make sure it slips into it’s cup.
Having rebuilt the bike time to take out the top nuts, so put the bike on a stand and let the legs
extend. I use around 150cc per leg of SAE 10 but you can go heavier or lighter if that’s your
choice. Pour the oil in SLOWLY or you may get an airlock and lose a lot of oil as you are trying to
fill. If this happens…..don’t guess! Drain it off and start again.
On the TY250’s replace the top nuts and then tighten the top yoke clamp and refit the top
rubbers if they haven’t been lost. on the TY175’s remember the legs fit proud if you are using
standard rear shocks, if you change the length of the rear shocks you may need to consider
changing the length at the front or it will handle like a Harley!
Don’t forget the other 110 articles, find them all by looking in Archives Oct/Nov/Dec