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 wont get done anyway?
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 don’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 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