Fork servicing, part 3 – re-assembly.

This is the last part – I promise! Time to re-assemble the forks and get them working the way the Yamaha engineers intended. Which is nothing special I might add, but at least they soak up a few bumps without banging and leaving oil all over the place!

So what do we need? Tools were covered in Part 2, but the new parts were not. I will be doing a post on after-market seal options in the future but we will assume genuine Yamaha parts at this stage. Oil Seal: 1T3-23145-00, Dust Seal: 4G0-23144-01 and if required, Retaining Clip: 4A1-23156-00, 600ml of 15Wt fork oil (1 litre bottle is what you need). If you shop around I’d say the job should be done for not much over $50AU. If you use after-market parts (or shop from the US) you could knock $20 or more off that cost.

Now that the inner and outer tubes are nice and clean, stick the outer tube horizontally in the vice and slide the inner tube into it. Slide the tube in and out to make sure there is no binding and use your eye (line the inner tube up with the edge of your bench) to rotate the inner tube to see if there is any misalignment, and therefore see if the inner tube is bent. Remove the inner tube if you’re happy with the fork operation.

In my last post I showed a picture of the lower section of the inner fork tube where the inner tube bush should go. While we have the two fork sections apart, give this section a close inspection. This area is usually quite worn to the point where the chrome has worn off the leg. No one is going to spring for a new inner tube though right? So either nick or mark the top of the tube where it lines up with the wear so you can reassemble the tube in the triple clamps 90 or 180 degrees so you are on some fresh chrome.

Sound dodgy? Well, it is but the inner tube is pricey from Yamaha, to the point that it might be worth more than the bike. Re-chroming is also an option, I guess it all depends on what sort of maintenance/restoration you intend doing.

Use a piece of 2000 wet and dry paper lubricated with fluid (kero, diesel or non-water based wash fluid) to linish the chrome of the inner tube. Rotate the tube while you hold the paper on it so the light marks you leave on the chrome will be at 90 degrees to the movement of the fork tube. You may feel imperfections that you can’t see so if you feel anything big holding up the paper, give the imperfection some more attention, you may need to move up to a heavier abrasive to repair the section so it won’t damage the new seals.

This method will clean up the chrome and make work much easier for the seals. Also clean up the inside of the top of the inner tube where the fork cap screws in. This is where the o’ring for the cap seals the fork – clean is good.

Most corrosion on the inner tubes will be above the area where the inner and outer tubes move, in other words between where the triple clamps hold the forks. It is very common for this to happen on the AG200 and is one reason why I like to assemble the new seals in the outer tube before inserting the inner tube. It prevents damage to the seal by lowering it down over the rusty inner tube. This is contrary to most other methods of fork assembly but I think that a little bit of attention to inserting the seals takes away all these other issues for medium to long term durability of the seal.

Of course another reason is you don’t need a fork seal driver. I have one and can do it this way but since the AG200 doesn’t have a inner leg bush, it all goes together quite nicely and you can insert the seals before assembling the inner and outer tubes and not have to worry about damage. It just means you have to be more vigilant while installing the oil seal. You could of course assemble the fork with dust and oil seals already installed from the bottom of the inner tube to avoid the damaged chrome (assuming it is damaged of course), but it doesn’t leave much room to install the oil seal with a slide hammer without pushing the dust seal up the tube into the damaged chrome in the triple-clamp area. Do what works best for you.

Give your inner tube another clean-up to remove the grit from the wet and dry paper. Give the inside of the outer tube a blast with carby or brake cleaner (careful of paintwork) to make sure it’s all clean. Place the outer tube in your vice, use some rubber grease (normal grease is OK) to lubricate the outside of the seal. Apply a bit to the mating surface in the outer tube as well. Make sure the seal is installed the correct way up (lip spring facing the bottom of the leg)

Now comes the tricky part, the oil seal MUST be driven in parallel to the outer tube. It must be even as possible without one side of the seal hanging up as it goes down. You only really get one chance to do this right, if you have to pull the seal back up you will wreck it. Patience and being observant will win the day. Some heat on the outside of the outer tube may help with this procedure as well if you have a heat gun.

Use the old seal on top of the new one and drive the new seal down with a hammer. Take one tap and observe what the seal is doing and try and correct any unevenness as it goes in. When you see the groove in the outer leg for the retaining clip, you are close. The seal needs to be even all the way round and the clip needs to be able to go in, when this is achieved you are done. Install the clip, put some lube on the dust seal lip and install the dust seal. You should be able to do this by hand. This is a good time to get some grease on the oil seal lip as well.

If you have got this far then most of the work is done. Use some 15Wt. oil to lubricate the damper rod piston and slide it, with the small rebound spring, down the inner tube so the rod slides out the end. Install the spring, washer, spacer and end cap. No need to screw the end cap up too far yet because it’s all coming apart again in a minute. Place some oil on the end of the damper rod where the collet fits on the end, fit the collet and use some fork oil to lube the damper rod and the outer tube bush below the oil seal. The inner tube can then be carefully installed into the outer tube.

Looking into the damper rod bolt hole at the bottom of the outer tube, use your pick or a fine screwdriver to align the damper rod with the hole as you push the inner tube down the outer tube. Now the damper rod bolt and the copper washer (renew it if it looks indented or otherwise damaged) can be inserted and done up.

Because there is no oil in the assembly, you will find that compressing the fork to put pressure on the damper rod to stop it turning, will work much better than when we pulled it apart – no oil = more friction. The Yamaha manual specifies 30Nm torque for the damper rod bolt so if you have a torque wrench you can put it to good use here. If not…don’t do it up too tight, 30 Nm isn’t a lot. The Yamaha manual says to use thread locker, I don’t.

Remove the top cap, spacer, washer and spring and check the operation of the fork assembly for smooth and correct operation. If all is OK place the fork assembly vertically in the vice. Measure out 294ml 15Wt. fork oil and pour it into the fork assembly. I pump the fork up to the top of its travel to the bottom 10 times to pump all of the air out of the system. I then go and have a latte while the air rises out of the oil. You don’t have to do this of course but I love my coffee!

I then use my oil height tool (117mm from the top of the inner tube to the oil level, fork tube collapsed) to suck out any excess oil. The height of the oil is more important than the volume but you don’t have to get too particular, especially if you don’t have the tools required. Actually I have all the tools that the manual and the experts on Youtube use, but I was also bought up on a farm where we had to make do with nothing. The AG200 can be worked on with minimal special tools and I try to give tips in avoiding them when I can. I realise that most people with these bikes are on a budget, I understand because I was too.

Extend the fork up to its full height, install the spring (spring free-length should be 403.5mm and no less than 399mm) and make sure the tighter pitch section is at the top. Drop in the washer, spacer and then lube the o’ring and thread on the top cap with a bit of grease and screw it in to the fork. We are finished! All that needs to be done is to tighten up the top cap (23Nm) and can be done in reverse of the Part 1 procedure to undo them. I suggest spraying some chain lube or similar into the hex section of the fork cap before putting the plastic cover back on. Water seems to find its way in under this cap and it will rust pretty bad if you don’t protect it.

The installation is pretty much the reverse of Part 1 taking note that the top pinch bolt (1 x 14mm bolt & 17mm nut) is set to 34 Nm, while the lower pinch bolts (2 x 12mm) are set to 23Nm. Also take note of the nick or mark that I advised to put at the top of the inner tube as discuss earlier in the blog. As mentioned, if you rotate this mark 90 or 180 degrees you won’t be running on the section without hard chrome.

Also take care aligning the speedo drive up when installing the wheel. If you don’t align it properly, you will bend the speedo drive tabs and it can jam and destroy the whole speedo drive assembly, have seen this many times.

So there you go, all done! Fresh new forks working as they should. Now get that bike back together and enjoy your handy work…

Cheers

AGman

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Fork servicing, part 2 – disassembly.

Welcome to Fork servicing 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 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. If the damper rod spins in the leg, 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 the fork is in really bad condition, there will have been water in the tube and the damper rod components will have corroded 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 won’t 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 wouldn’t work 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, I’ll discuss an alternative method in the reassembly section.

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 the 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 will a bit of heat from a hot air gun if you have one. Just give the area on the outside of the leg where the seal sits a minute or so of heating and it will make things a bit easier for the seal to pop out.

Once the oil seal is removed, clean this area 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. This is why I think drain screws are pretty much a waste of time on most bikes. This rubbish is hard to move with just an oil change.

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? Can’t wait for the engine rebuild eh? 🙂

Cheers

AGman

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Fork servicing, part 1.5 – a discussion…

Before I go on with part two of my fork servicing article , I’d just like to talk about a few things here first. It dragged out the second post and I felt it distracted the reader from the job at hand of servicing the forks, but it’s info I feel the owner needs to know so here we go…

About eight years after the release of the AG200, Yamaha removed the drain screws on the fork legs. In the 1991 AG200B owners manual, they deleted the fork oil change description so I’m guessing that this was the first year they removed the drain screw. In fact, there was three iterations on the AG200 fork leg; The first seven to eight years had drain screws, then the forks had the casting on it for the screws but they decided not to machine a hole, tap a thread and insert a screw. And finally they changed the casting and removed the facility to drain the oil altogether.

It seemed to be a manufacturing policy at Yamaha that effected a few of the lower-end models with conventional forks like the TW200 and DT175. If you check out forums on these bikes you will read up on people moaning about Yamaha being cheap and conspiracies flying around that it was a deliberate ploy to reduce the life of components on the motorcycle. The theory was if people can’t easily service the bike they won’t.

I’m not sure if I buy into these arguments – here is my take (in relation to the AG200) on the issue; I thought it was a good idea to remove the drain screw. Why? I think simply dropping the oil in this design of fork is a waste of time. After servicing suspension components for a while, you soon learn that if the oil comes out dark something is wrong. In the case of conventional forks, it usually means you have worn through the low friction coating on the bushes in the inner or outer fork leg. When this coating is worn your chewing into the bush material or the aluminium of the fork leg (or both) hence the dark colour of the oil.

With the AG200 forks there is NO bush on the inner fork leg which means you are always chewing into the aluminium of the outer fork leg! The oil is going to get darker a lot quicker and will need more servicing to prevent premature wear of the forks. In the case of the AG200, why bother making something easy to service when it won’t get done anyway? The other low-end Yamaha’s are pretty much in the same boat as well, few change the fork oil until seals blow out so who cares about serviceability?

To me there are only two types of people who own motorcycles (or any other machine for that matter) those that don’t care about maintenance and those that do. I’d say that it is around a 95% to 5% split respectively! Those that do can be broken down again to those that do care, but want someone else to do the spanner work for them, and whose expectations are usually let down by their selected service department, Yamaha or otherwise.

So if you look at it from Yamaha’s perspective; why make the thing easy to service? 95% of owners aren’t even going to get them looked at until they spew oil out everywhere and even then they usually just let it fill with water! The other 5% should know better and do the job properly by removing the forks from the bike, disassembling them and cleaning them up properly.

One other thing to keep in mind with the AG200 is that when the fork seals fail, farmers just leave it. Even when it starts topping out and banging away metal to metal down there they still leave it. I suspect that the plastic material they use for the fork boots doesn’t like oil because they seem to split and fail fairly quickly as well, mainly in the lower sections which is what makes me suspect it’s the oil that hastens this process.

Now that the forks are empty or low on oil, the failed fork boots allow water and dirt to accumulate in them and under some weird act of physics actually suck water into the fork! So don’t be surprised if you drain more water out of the forks than oil, I have seen it plenty of times before. It is also another reason to totally disassemble the fork – you may need to remove old oil, dirt, metal deposits, water and corrosion on steel components!

People have asked me can I drain the oil out of the forks without removing them? Yes, technically you can but I have never done it and never will. If you follow my part 2 article closely you will see how it can be done, but I wouldn’t. You will never get all the old oil and sludge out and with this design you really need to. Even if you decided to flush them on the bike the fork cap directly under the handlebars makes this a pain. I just prefer to remove and disassemble them, clean them up and put them all back together with fresh oil. That’s just me.

If the fork boots are good and there is no accumulation of rubbish on the dust seal, then you can probably disassemble the fork without replacing the seals. I have done it plenty of times before. You just need to be gentle on the seals and make sure it all goes back together clean with nice fresh oil. If there is any rubbish around the dust seal and the oil looks dark and old, replace everything – oil and dust seals. Then you wont have issues any time soon and have to tear it all down again.

This ends part 1.5

Cheers

AGman

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Fork servicing, part 1 – removal.

OK folks, it’s time to get serious. Time for some real world maintenance and to show how it’s done. The service manual is useful but it can only get you so far when it comes to common faults due to poor manufacturing or (more commonly) owner neglect. And who really wants to buy all those Yamaha service tools? The AG200 is a simple bike and can be maintained easily and cheaply with some tips to avoid expensive tools. So lets jump in with this first installment showing how to remove the forks.

So what tools are needed? A couple of bricks(!), 10, 12, 14 and 17mm spanners, #2 Phillips head. You will also need a 19mm hex/Allen key. There are two ways of doing this; you can go to a tool shop and buy one like shown on the left, or you can go to a fastener shop and buy a bolt with a 19mm head and bash/weld it into an old socket, as shown on the right. You may have an old socket kicking around and a 19mm hex bolt so the latter version will be cheaper to procure.

I have both but actually prefer the latter because it can be used to separate the inner and outer fork legs (the black 1/2″ drive hex tool shown wont fit down the inner tube) if required which I will cover in the second part of this “how to”. So why not put some nuts on the end of the bolt and lock them? You can do that but when we get to part 2 you will see where the drive component of the socket may come in handy.

OK, first thing is to grab your bricks and put one under each stand, one on the left and one on the right. This will make the bike nice and solid to work on. Just be aware that the weight will be slightly forward biased, when you remove the front wheel, the bike will want to fall forward – just. Another brick or two might be necessary for your workshop tool kit! Just place them on the rear pack rack.

Back to the job…back off the front brake adjustment up on the handle bar. This is to get the pads as far away from the linings as possible to aid removal. Remove the front brake (10mm) and speedo cable (#2 Philips) brackets on the left (sitting on the bike) fork leg. If they look corroded they will be a pain to get off. With the plastic speedo cable bracket just cut it off and you can either re-secure it with a new one from Yamaha (part # 3R9-23318-00) or a cable tie will suffice if you don’t care about appearances (not too tight though – you don’t want to cause the outer metal sheath to put pressure on the inner, rotating cable). If the bolt breaks off on the brake cable clamp then you can drill it out and put a 6mm bolt through it.

This is what I am talking about with the manual, the two components I talked about above are out in the open and due to the conditions that these bikes are accustomed to, they corrode and become service issues. It happens a lot on the AG200 and the manual doesn’t help you out that much when you have a problem with them.

If the fork boots are OK and you want to save them, pull the vent hoses out of their routing tabs (1) and slide them out of the headlight assembly. The tubes don’t separate from the boot so don’t force them or they will break. Undo the top boot clamp (2 – #2 Philips) and twist the boots so they come free of the fork leg and can slide around easily. A bit of silicon spray or WD style spray may be helpful here.

Now we can undo the axle nut. On older bikes with a castle nut and a split pin, this will be a 17mm item, while later bikes have a 14mm, self locking nut. We can now slide out the axle. Be vigilant of the balance of the bike as you remove the axle. When the axle is out, you can rotate the right leg (this is why we loosen the boots off as well) to aid in the removal of the spacer, this then gives you a bit more manoeuvring room to get the brake pads and backing plate assembly out of the brake hub. This should free up the whole show so the wheel can be removed and put aside.

Next is fork removal. Undo the top (14+17mm nut & bolt) and bottom (2 x 12mm bolts) clamp bolts and be prepared to catch the fork as it slides down. Corrosion on the fork legs may prevent this! CRC/WD will help if it needs it. OK, its time to get our 19mm Allen key or specially constructed tool into action. Because the handle bars run right across the top of the fork cap, we can’t get a tool in to loosen the cap without taking off the handle bars – no need for that! Slide the fork down in the clamps so you can get to to the fork cap with your 19mm tool. Nip up the two lower clamp bolts and you can then pop off the plastic cap cover, insert the hex tool and loosen the cap nut, but don’t remove it.

Loosen off the two lower clamp bolts and you can slide the leg out. Do the same for the other side. Remove the fork boots, give them and the forks a clean up with warm soapy water if covered in crud, dry them off and we have two forks ready for strip down and service.

This ends part 1.

Cheers

AGman

P.S. Like my content? Has it helped you out with your AG200? If it has provided value to you and you would like to help me to continue adding content and information, check out my About/Donate page for info on doing just that! Thanks to those that contribute.