Welcome to part 2! This is the nitty gritty of AG200 fork servicing. It’s the bit where you have to have your wits about you because if you rush it, you can easily stuff it up! We don’t want that so PAY ATTENTION! I don’t want you turning a perfectly good set of forks into an oil pump! Seriously, its not that difficult and I will explain why I do the things I do and why you need to pay attention in certain areas that could end in tears if you don’t.
So what tools will we need? 6mm Allen key, the 19mm hex/Allen key special tool we discussed in part 1 (and a T handle and extension if things don’t work out), tyre lever, pick or something pointy, a wire brush, a sturdy bench vice with protective jaws make it all a lot easier too. In fact I can’t imagine doing this job without it. Facilities to give all the fork components a good clean up is nice – a parts washer is perfect but a bucket with some solvent and a stiff brush will do the job too. A can of carby or brake cleaner comes in real handy as will a lot of rags.
OK, first thing to do is place the outer tube in the vice horizontally and give the bottom of the fork leg a jolly good clean up. Grab your pick or other fine tool and clean all the crud out of the 6mm Allen bolt (damper rod bolt) at the bottom of the leg. Make sure you clean all the crud you can between the circumference of the bolt and the outer tube, compressed air is good if you have it at hand. If there is a lot corrosion on the bottom of the aluminium outer tube then you may need to hit it with a wire brush and some CRC/WD.
You can now stick your 6mm Allen key into the damper rod bolt and try and release it. If you have been watching YouTube videos on dismantling conventional forks, you will know that there may now be some issues. Once the damper rod bolt comes loose, it may just turn the whole damper rod assembly inside the fork leg preventing it from unscrewing. So what do we do now? Well the manual says we can use the special damper rod holder tool to hold the damper rod but I just compress the fork leg a bit (see pic below) and the spring will put more pressure on the damper rod and hold it while you undo the bolt.
For me this works nine times out of ten. For the other times is when you will need the special 19mm tool with a 1/2″ extension and slide it down (after removing the cap, draining the oil, removing the spring and spacers) the inner tube to hold the damper rod. I find that if a fork is in really bad condition, there will have been water in the tube for a very long time and the damper rod components will have rusted and will need some extra love to get them all apart.
So assuming the damper rod bolt came out OK, you should turn it so you can undo it with your fingers but not all the way out. Remove the fork from the vice and place the fork over a container and remove the bolt, watch out for the copper washer under the bolt. Have plenty of rags on hand in-case they are needed. After the initial oil has drained, slowly pump the fork to remove as much oil as possible. Be aware that the fork will now separate so be really careful when extending the inner and outer tubes apart, especially if you don’t plan to replace the seals.
When you think the majority of the oil has drained you can now gently separate the two fork components. It’s probably best if you do this procedure back in the vice with the outer leg mounted horizontally, be gentle with the seals if you aren’t replacing them. The outer tube is in the vice and the inner tube will look like at left. If watching the above mentioned YouTube vids, you would of looked on in horror as people use their lovely front suspension components as a slide hammer, bashing them apart! Well luckily you don’t have to do this with the AG200 fork because there is no inner tube bush to hang up on the outer tube bush as they come apart.
Now we have two separate components. Put the outer tube aside (beware the damper rod collet or oil lock piece – see below) and we can divert our attention to the inner tube. Undo the top cap (you did loosen it per the instructions in part 1 right?) of the inner tube and remove the spacer, washer and spring. Keep some rags handy as you remove these components because there will usually be some oil left in the inner tube. The damper rod will now be free to slide out the top of the tube as well depending on whether the oil lock piece stayed on the damper rod or stayed in the the outer leg when separated.
The photo at left shows the components talked about above. 1 is the inner tube. 2 Shows where the inner tube bush usually goes on conventional forks! 3 is the damper rod and 4 is the pesky collet that can get corroded.
I find if the forks had water in them and there was a bit of corrosion, the collet may stick to the damper rod and might need a bit of persuasion to come off. Once free from the damper rod you can turn the whole inner tube upside down and the rod and the small rebound spring should slide out of the tube. All these inner tube component need to be thoroughly cleaned and any corrosion removed. Pay attention to the thread on the inner tube where the cap screws in. Make sure any corrosion leading up to the threads is removed with wet & dry.
Now lets turn our attention back to the outer tube. Give it a bit of a scrub up but there is no need to get too fussy because there is still work to be done here. I prefer to do all the work on the seals while the two tubes are separated. Why? Because nothing will go near the delicate chrome surface of the inner tube if you work this way. If you fumble removing the dust seal or retaining clip and gouge the chrome on the inner tube, then you have stuffed it! It will never stop leaking oil or it will damage new seals that you will install. Even if you put it all back together and it works OK you have created an area for corrosion to set in. Get the two tubes apart and away from each other and this wont be a problem.
Another reason why I do the fork seals the way I do is because 80% of AG200s I have seen have rust and pits on the chrome fork leg between the upper and lower headstem clamps. So if you do the seals like they show you on the Youtube videos, you will have to slide the new oil and dust seal down over all this dodgy chrome. In the next part I show you how to clean up the legs but damaged chrome is damaged chrome. It WILL hurt your seals as you slide them down over this damage. If the AG200 forks had an inner tube bush, my procedure would be harder to pull off but it doesn’t so we are on easy street. The only thing we have to watch is getting the oil seals in even and square. We just need to be more careful when we do this job…but I digress…
Place the outer tube in the vice as low as it will go to reduce the force placed on your bench and vice. Grab your tyre lever and use it to lever out the dust seal. I use a piece of rubber under the lever to protect the top of the outer tube. Your thinking why use a tyre lever right? Why not just use a screwdriver? While removing this top dust seal (which will be easy compared to the oil seal under it) be really careful you don’t scratch the aluminium on the inside of the outer tube. A tyre lever will have less chance of damaging this area as opposed to the sharp corners of a flat screwdriver. It’s probably not so important where the dust seal fits, but it is critical for where the oil seal fits.
Underneath the dust seal is the oil seal retaining clip. See the pic. at left where 1. is the clip, 2. is the oil seal and 3 is the outer tube bush discussed bellow. I suggest that you leave off purchasing parts for the forks until you have it all apart to see what is actually damaged. If the forks are old and the fork seals have failed then there will probably be dirt and corrosion between the dust seal and the oil seal. If the clip is rusty, replace it. Be careful removing it, place a rag over the top of the tube as you lever it out blind. There are two reasons for this; the first one is obvious; the clip can fly out and take out an eye. The other reason is not so obvious. If the seals have failed and there is oil, dirt and rust in there, the spring can flick back into its slot and not come out but in the process of springing back home it propels rubbish out and into your face. Don’t ask me how I know this!
So the dust seal and the retaining clip is out, now it’s time for the tough one – the oil seal! It’s not that tough really but you just have to be careful not to damage the surface that the seal is pressed into. This part of the fork is under pressure so anywhere the pressure can escape it will. You damage this surface and medium under pressure will escape past the seal. Because it is further in the tube it makes the tyre lever a bit more awkward to do but take your time and it will come out. Removing as much of the crud above the seal will help as well.
Once the oil seal is removed, clean this area to as close to perfection as you can. Use grade #2000 wet and dry paper to clean up the area where the seals press in. Use your pick to clean out the retaining clip groove. Be careful of the bush just (see above) below where the oil seal was, and try not to nick or scratch the anti-friction coating on it. Of course, if the bush is really worn you will need to replace it but surprisingly, it’s quite rare for it to fail.
Take a good look at the inside of the outer tube and there may be an accumulation of black sludge at the bottom. This is where brake cleaner can come in handy for cleaning this up. Get it as clean as you can and jam a rag down there to clean out the residue. Give the whole outer leg a good clean up and look over, throw away the dust seals and retaining clips if they are damaged but hang onto the old oil seals for now because we will use them to drive in the new seals. Just give them a bit of a clean so you don’t put crud all over your nice new seals and clean components.
So everything should be cleaned and ready to go back together, soooo this ends Part 2. It just got too long! I bet you didn’t think it would be over 3500 words to describe this procedure? Cant wait for the engine rebuild eh? 🙂