Tag Archives: dust seal

Fork servicing part 4, alternative parts & tools.

Oh no…not more fork stuff from this clown! Yes but there is nothing more about working on them. This is about the parts used in them and what we can use from other models and other manufacturers. I also have a few tips on tools…lets take a look…

First of all, here are some dimensions that might come in handy if you are researching fork info for this bike. The inner tube is 35mm in diameter, this is the inner measurement for the oil and dust seal. The outside diameter of the oil seal is 48mm. The dust seal has an outer diameter of 48.5mm I presume to help with the interference fit in the fork because of its smaller thickness compared to the oil seal.

Some of the other Yamaha models that use the same seal are; YZ100 ’80-’81, DT125 ’82-’83, IT125 ’81, XT125 ’82-’83, RT180 ’90-’93, XT200 ’83, RD250 ’78-’79, RD250 ’76-’79, TZ250 C-D-E, XT250 ’80-’83, RD400, XS400, SR500, XJ500, XS500, XV535 ’88-’92, TZ750 (!!!). Some alternate Yamaha part numbers for the oil seal are; 10V-23145-00, 38W-23145-00, 1UA-23145-00, 29L-23145-00. Don’t quote me on all this, it’s just what I have found while cross referencing stuff. There is no way I can confirm this 100% because I don’t own or have serviced all these bikes. What I do know is that the YZ100 does fit.

As for after-market suppliers, some don’t even have a listing for the AG200 but you can go on the dimensions – Fork oil seal 35x48x10.5mm (35x48x11mm is also fine) ARI has a listing as ARI.003T, Vesrah – AR-3506, Emgo 19-90134 and Allballs 35-1011. The dust seal is a bit more complex because some hang up over the fork tube so it’s hard to say what their correct height is. The factory dust seals measurements are 35×48.5x5mm. ARI do a listing of ARI.049 but I notice the thickness is larger (8mm) but this may be because the design is different like the Pyramid Parts seal that I have tried and discuss below. Allballs do a kit listed as AB55108. I have never ordered any of these parts or kits except for the genuine parts and Pyramid, so do some research of your own if you’re going to go your own way.

Fork seal kitI have checked a lot of the after-market companies and their listings and have found a supplier called Pyramid Parts that sell a kit that is quite good quality. Their product code is F&D 013 & 066. They don’t have any listings for an AG200 but, as stated above, I do know that the 1981 YZ100H has the same fork seal dimensions as the AG200. I have purchased a few of the dust/oil seal kits and they work well. In fact, I think they are better than the genuine items. I haven’t had them running for extended periods as yet but the oil seal has a tension spring on the upper and lower lips while the dust seal has multiple lips that should work much better than the original.

Dust seals compThe only hitch is that your fork boots may hang up on the top of the dust seal when you lower the boot down on it. I have installed two sets of these seals so far and this only happened on one installation and only on one leg. I still managed to get the boot down OK and fastened the lower section of the boot with a cable tie. I suspect it was just the boot in this situation (it was a bit wonky). You can see in the photo here that the after-market dust seal on the left sits up higher on top of the fork, while the original dust seal on the right sits down in the outer fork housing flush with the top.

The YZ100H were shipped from Yamaha with fork boots but maybe it was a different design to the AG with more room at the lower section of the boot? Or maybe its just a oddity of the the after market? It is a much better dust seal than the genuine AG item, to the point where you could run the forks without the boots if they are damaged. So this kit is good for a few reasons – if your boots are wrecked, leave them off and just use this superior dust seal. If your boots are OK then you have the protection of them AND a better dust seal – you cant loose.

Fork seal kit#2Pyramid Parts has a shop on ebay Australia that sells these seals at $25.00 for a kit. It’s cheap and even comes with a little tube of assembly lube which is cool. Just be aware though, his feedback is poor because he is sloooow! You will be waiting for two weeks to get anything out of him but that is my experience of anything out of New Zealand. You can’t rush these Kiwis! ­čÖé He says it’s Australian stock but from the mirth of his feedback I find it might be stretching the truth a bit. But who cares? You want stuff cheaper then something usually gives, in this case it’s the delivery time. Maybe I should do a bulk purchase from the company via their website and sell them myself? let me know what you AG200 owners think about this and I may start my own AG-only parts thing up.

Fork circlipIf your forks are full of water, which is pretty common, then the oil seal retainer clip will be in pretty poor condition and I strongly recommend replacing it. Any old garden variety bearing shop should have, or can order in, some internal circlips to do the job. Just ask for 1.75mm thick by 52mm internal circlip. Make sure they are seated correctly in the groove and they will do the job fine. You can get stainless ones too ($$$) but if you maintain your forks you shouldn’t get moisture past the dust seal. You will need to update your tools, a proper set of circlip pliers will be needed of course.

What about fork oil? Fork oil is hideously expensive for what it is. I pay well over $20 for 500ml. It’s too much I reckon. I have read around the web that a lot of people use Auto Transmission Fluid. Never tried it myself but I can understand why people would. I will stick with the proper stuff with my bikes but I can’t see how ATF would hurt on our more lowly steeds. It is just hydraulic fluid after all. The AG needs 15wt oil and I’m not sure of the viscosity of ATF, some say between 7.5 to 10wt so you may find the forks a bit quicker on the rebound action but what the heck…my view is that use proper fork oil if you can but if its a 100km trip to get it and/or you have a heap of ATF hanging around your workshop then give it a go.

Alternate oil seal driver!While we are on to alternate parts, here’s an alternative oil seal driver! The cam-chain side camshaft bearing in the AG200 is an alloy bush which I chuck out in favour of a roller bearing. It fits very neatly on top of the oil seal and does a good job of getting the seal in even. I will document this mod in an up-coming post so you too can get your very own, genuine Yamaha fork seal driver!

In my fork repair posts I also noted that you need to weld a 19mm bolt into a socket, well Fork damper holderthere is a cheaper way of getting that tool into your AG200 toolkit; just weld a 19mm bolt into a piece of pipe or on the end of piece of steel bar – what ever you have lying around really. Weld another piece of pipe or bar at 90┬░ on the other end to make a big long T-bar tool (check out the “damper rod T-Bar tool” in the Yamaha service manual). Many moons ago I did this to get the forks apart on a road bike and it worked a treat so it will do the job for the AG. The bolt into the socket tool mod isn’t that expensive, but acquiring the 1/2″ extension and T-handle can add up. Just make sure the length from the bolt end to T-handle is around 55cm or longer to reach into the fork properly.

So there you have it…I don’t think there needs to be any more info on AG200 fork maintenance. We are done.



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!

Fork parts2So 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.

Insert tubeNow 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.

Inner tube wearIn 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 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.

Cleaning inner tubeUse a piece of 2000 wet and dry paper lubricated with fluid (kero, diesel or non-water based wash fluid) to run up and down the chrome of the inner tube. You will feel imperfections that you can’t see. It 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 two tubes and not have to worry about damage. It just means you have to be more vigilant while installing the oil seal.

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.Oil seal instal 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)

Install oil sealNow 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. Use the old seal on top of the new one and drive the new seal down with a hammer. Oil seal inTake 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.

Install damper rodIf 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. Damper rod installedPlace 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.

Fit colletLooking 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 can be inserted and done up. Aligning damper rodBecause 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 Instal damper rod boltyou 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 and I use a small amount of weak thread locker on the threads of this bolt.

Remove the top cap, spacer, washer and spring and check the operation of the fork assembly for smooth and correct operation. Oil fillIf 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!

oil measureI 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.

Spring pitch#1Extend the fork up to its full height, install the spring and make sure the tighter pitch section is at the top. Drop in the washer, spacer and then lube the o’ring on the top cap 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 degrees you wont 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…