Compression does rise with engine speed, oil and throttle Opening.

TomHoldom wrote on 10/05/19 at 10:01:56:


Yes, no need to remove the stanchions and risk losing alignment. 

If the Allen screw just spins then the damper rod is rotating and you may need to drop a socket on a long extension down from the top to hold the damper rod still while you undo the Allen screw.  An impact gun would certainly get it loose without having to do that.  Even just tapping the Allen key with a small hammer will sometimes shock the screw loose.  ATF may be a little thick but worth a try if you have some. 190cc is correct but I prefer to measure the level with a dipstick touching the top of the damper rod. From memory the Level should be between 20mm and 50mm but you can check that in Haynes.  You can tune the forks between that range as it is effectively changing the air spring when the forks are compressed.

Don't overtighten the Allen screw as next time it can mean that instead of coming loose the damper piston unscrews off the top of the damper rod.

13mm is correct. As you will have to remove the top plugs and springs, the fork leg can be collapsed to reduce the length of socket extention needed. I can't give you an exact length but 25cm is in the ball park. I need to string a couple of shorter ones together.

Did you try to shock the Allen screw loose ?   Given that it's only pressure from the main spring that resists rotation of the whole damper rod, another option to try is to increase that pressure by compressing the leg by hand while trying to undo the screw. Not easy and possibly a two man job.

still stuck on doing up that first side, but in the meantime have taken the other side apart to find quite messy splodge on what I think is the damper rod seat - see photo
Is this something disintegrated which needs replacing?

Tom,   You should be able to tighten it again by compressing the leg. I know there is a torque spec but it only has to be tight enough for the leg not to fall off and tight enough for the oil not to leak past the washer.

To remove the top plug if you need to, push the plug down against the spring pressure until the wire circlip is exposed, dislodge the circlip with a small screw driver and fish it out. The plug will then pop up when you release it.

The damper rod seat is called the top hat for obvious reasons. Besides holding the damper rod central they are usually tapered if not as much as the illustration shows. The reason for this is that on full compression of the forks the tapered section of the top hat enters the valve body and restricts the flow of oil to act as a hydraulic bump stop.

The sludge may be what's left of the topping out bump stop which is item 12 in your illustration. They were originally made of black rubber and it's highly likely to have  disintegrated especially if the forks have never been apart before. The valve body assembly which you don't see comprises items 12 through to 17  and lives up inside the fork stanchion. Remove the large circlip item 17 and the valve body will drop out. It can be done with the main spring in place but be careful as the spring will push it out.

Might as well go the whole hog now having found the sludge.

I wouldn't wash it out with water, at least not in the first instance, perhaps a very hot water and detergent rinse to finish off. You need a solvent that will dissolve the crude. I'd use whatever you have to hand, paraffin,  diesel, or even white spirit.

If you are not intending to remove and inspect the valve body assembly to see if the topping out bushes are still there, then at least measure the length of damper rod protruding from the stanchions. If they are not the same length then one of the bushes has disintegrated for sure.  The bushes are intended to absorb the shock of the forks reaching full extension although there is also a hydraulic bump stop effect if the forks are working properly.  In the very worst case it's not unknown for repeated topping out shocks to shear off the damper piston.