Fix Fork Leg Compression Damping

[gsxbarmy]

NOTE: This thread is also available to download as a PDF file from the Downloads (General) Section

Fork Leg Compression Damping

The compression damping adjuster on my fork legs were stuck fast ... with a drill, some heat and lots of patience I've got them apart and thought you may like to see how it all goes together for reference (in case you need to do it at some point).



The damper adjuster has two o-ring seals, one at either end ... the seal nearest the yellow arrow is to stop crap from the outside world getting into the inners of the fork leg, while the second seal is the actual oil seal (which is the important one). Midway between the two seals is a small threaded section which engages in the threaded section inside the fork leg.

The detent plug, spring and ball bearing are installed into the hole in the side of the fork leg with the ball bearing engaging in one of the four slots milled lengthways in the damper adjuster ... this is what gives the 'click' as you turn the adjuster.

The small stepped section of the damper adjuster moves in and out of a hole in the fork leg, thereby controlling the amount of oil which passes through the banjo bolt (this controls the flow of oil between the inside and outside of the damper rod I think).

The detent plug is basically like an open topped tin ... it's a press fit into the fork leg, with the spring up inside it pressing down onto the ball bearing.
To get the whole lot apart requires that you (very carefully) drill the end of the plug out so that the spring and ball bearing can be removed, which then allows you to remove the damper adjuster ... this is where I needed to use heat and WD40 to get some lubrication between the outer seal and fork leg, since this is where corrosion builds up.

I'll need to get some new plugs obviously, but if I can't find them anywhere then my plan is to get some brass rod and make a new plug up which can then either be press fitted in or fitted with a wee bit of thread lock.

A few comments:
-   Diameter of hole in fork leg is 5.00mm
-   The plug that is drilled out is a press fit. The problem with the current setup is that you need to destroy the plug to get it out. The little plugs I’ll make will fit once I either drill the hole a little larger, or put them in a drill and rub them down a little bit so that they press fit in ... I'll still be using a bit of thread lock though for security. The main thing is there shouldn't be any oil in the section where the ball bearing is, that's what the first seal is for ... the secondary seal (at the slot end) is just to stop crap from the outside world getting in ... so your seals are definitely damaged if you're leaking fork fluid. The o rings are simple straightforward jobbies,  1.8mm thick, inner is 10.5mm and outer is 12.5mm (outer diameters) ... best I can measure with the calipers. My outer o-rings were gubbed due to corrosion and heat damaging them (heat was to get the adjusters out).
-   The other way to do this is to use an M6 bolt with a 3mm (maybe 3.5mm) hole drilled in the end to take the spring, then tap the plug hole to M6 which this means you can then thread lock it (and undo it again if need be).

[Paul Weaver]

This is a really good post for me as my l/h adjuster leaks when adjusted fully out. Are the o rings available seperatley?

[gsxbarmy]

Not that I know of Paul, you'll need to find a supplier to purchase them (although happy to be corrected)

[Paul Weaver]

Dave - are the adjusters available to buy anywhere? Do they just drop out if you continue unscrewing them? I want to replace my l/h for sure and if they are available to buy I'll do both.

Cheers.

[froudy]

@Paul Weaver

I've had a look on Robinsons site at parts diagrams and the adjusters aren't shown as a separate spare.
I would still give them a call though as they do sometimes stock parts which aren't shown in the diagrams.

PARTS & ACCESSORIES
01227 454 366

PS. I would hazard a guess that it's just the smaller, inner "O" ring causing the problem

[gsxbarmy]

Paul - what model is your GSX as the fork sliders are different on the K5> models. Just that I came across some very small o-rings the other day in my bits box, which might be just what you are looking for....if I can find them again (just off for a look )

[Bq]

I had to do almost the same with mine, due to some powder coating of the fork legs. I found a special worm screw to fix the clicking, simply threading an M6 in the place of the plug, turn in the worm screw and then fixing it with a lock nut.