The symptoms :
While riding along normally the
GL1800 rides wonderfully smooth until I had to slow down or stop. The anti
dive valve stays on until it decides to relax; during this time the front
end of the bike becomes skittish at very low speeds or while cornering.
The problem is also evident while negotiating speed humps in the road, I
always slow as I approach them and then release the brakes before I make
contact with them, but the suspension remains firm and seems to bounce over
the speed hump. The result is that the suspension can finish up almost
fully extended after crossing a series of speed humps. I once stopped after
crossing one of these speed humps and put the bike on its side stand and
waited almost 10 minutes for the front forks to relax back to the normal
position.
On the third time this started to happen I (being an engineer) decided to
take a look for myself.
The Fix:
The brake slave cylinder is the
problem, it forces a 5mm pin into the anti dive actuator to lock up the left
fork during braking. This slave cylinder is supposed to return upon
releasing the brake lever but it doesn’t always behave as it should, it
can take some time to return to its resting position. I took it upon myself
to effect a fix that works better than ever and has been working well for
the past year. My fix was to fit a small rubber 'O' ring over the pin and
remount the slave cylinder to its rightful place, that’s it!
Method 1:
The rubber ‘O’ ring is
2.5mm(0.098”) in section x 5mm(0.196”) bore and 10mm (0.393”) O/D made of
black silicone rubber, it sits in a void between the slave cylinder and the
anti dive actuator. It doesn’t impede anything or prevent anything working
it just helps the plunger to return to its rightful position.
To get at both the slave
cylinder and the anti dive actuator is simple… first, remove the top front
portion of the mudguard (top front fender) by unscrewing the four recessed
(5mm) socket screws. This brings the two units into view on the front of the
lower left fork leg, There are two (4mm) socket screws, one each side of
the slave cylinder. Undo these… (don’t worry the two items can be separated
and there should be no leaks, springs or nasty surprises) and insert the
‘O’ ring, checking first that your ‘O’ ring fits comfortably, without
friction, over the 5mm pin on the slave cylinder and in the 10mm recess in
the top of the anti dive actuator.
Method 2:
You can use two ‘O’
rings instead of the one.(above) The first ‘O’ ring dimension - 1.8mm
(0.070”)in section x 5mm (0.196”) bore x 8.5mm(0.334”) O/D and the Second
’O’ ring dimension - 1.8mm(0.070”) in section x 6mm(0.236”) bore x
10mm(0.393”) O/D, both black silicone rubber. The smallest ‘O’ ring sits on
the 5mm pin without friction and the larger ‘O’ ring sits in the recess on
top of the anti dive actuator, one on top of the other when assembled. Note:
when putting the two units back together be sure the ‘O’ rings are still in
place. This gives a slightly slower anti dive reaction under very light
braking. I favor this fix.
You can, if you’re daft enough,
(yep that’s me) ride the bike with the two units separated!!! but the bike
will dive every time you use the brakes.
WARNING
If you try to fill the void between the two units with rubber
the anti dive becomes next to useless. If your bike is still under warranty
let Honda sort it. If you have found a leak of any kind from either unit
STOP what you’re doing and inform your service centre.
Photos and their
descriptions (click on the pictures for bigger versions)
The front mudguard (fender) removed 4x5mm socket screws

Using a 4mm Allen key to detach slave
cylinder

The slave cylinder detached and not
leaking

The top of the anti dive actuator showing
the recess

The two rings I use are still in good
working order and the only two tool required for the job

The largest silicone ring in the recess

The smallest ring over the 5mm pin -
indicated by a screwdriver

Care taken to place the two items together

Securing the slave cylinder into
place using the 4mm Allen key

Finish up by replacing the front mudguard
(fender) using the 5mm Allen key

Happy Riding!
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