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.
I 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.
The 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.
Pyramid 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! 🙂 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.
If 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.
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 there 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.