@Professor: Not sure who your post was aimed at, the original poster, those who said "do both sides", or the shop. Nevertheless, yes to an extent you are correct. The forks are a unit once assembled. Where that generalization breaks down is that the two fork legs are independent of each other. That is, the only link they share is through the front axle. They don't share fluid or any other linkage. If the oil in one side is changed, and the other side is not, the two will have different actions. The older oil will be (probably) more viscous (and dirtier), and therefore the parts inside will wear differently. Yes, some bikes have split the actions of the forks, so one side handles compression, the other side rebound, and yes, some have even had a spring on only one side. However, most performance bikes, the Hayabusa included, have forks where both sides handle all duties. Thus, if one side is cleaned and refilled with oil, and the other has not, the suspension will not function properly.
Further, as pointed out elsewhere, before that one seal was replaced, both seals were (presumably) the same age. Just because one has failed and the other has not, doesn't mean the "good" one isn't days away from going out too. Just as you don't reuse gaskets on the engine, you shouldn't be "reusing" other worn parts either.
My post was direct to the OP because of the "balance" concerns. I've seen incorrect posts on this board before. Like stating the rebound and compression adjustments needed checked that they are the same because of uneven tire wear.
As a background I've owned a very small shop many years ago that I ran part time in outside my primary job. I've done suspension service on a Showa, KYB, and Ohlin components, front and rear. However the majority of it was motocross bikes. So I see both sides of it. If it was my bike I would service both sides. However I would not expect the shop to foot the bill for the other side. If it was my shop, I'd offer up to service the other side for a reduced fee to attempt to maintain a higher level of customer satisfaction. I would disassemble, inspect, reassemble with a new seal and wiper. If I saw damage while I had it apart, I'd even pick up the entire bill. However I can see why the shop would not be willing to do both and foot the bill for the entire project.
At 7500 miles it is still fresh. Ironically it is at the "factory service" mileage point where they are to be inspected." Inspect for oil leakage, scoring, scratches on tubes. Replace any defective parts." The service manual does not say " if parts defective parts are found on one side replace both" There are plenty of Busas that have gone 50K miles plus without touching the forks. So I wouldn't expect the other side to fail if there is no evidence of oil seepage currently. Depending on the shop I think he has as much a chance of them servicing the good side improperly as seeing it fail if left alone.
I disagree with this statement
However, most performance bikes, the Hayabusa included, have forks where both sides handle all duties. Thus, if one side is cleaned and refilled with oil, and the other has not, the suspension will not function properly. The remaining side is still functioning correctly. @ 7500 miles the fluid is still fine. The only thing that might be slightly suspect is the seal. There is a chance the other side failed to abuse. An abrupt set-down from an excessive wheelie could have damaged it but to a lesser degree. Small chance if it is not leaking now. In a dirt bike world, they usually get packed with mud between the wiper and seal. You just don't see that with street bikes.
With your argument, why wouldn't you be campaigning to service the rear shock as well? It has the same 7500 mile inspection period, on the same bike, subject to the same conditions.
If I have a tire fail on one corner of my car, I only expect the dealer to replace the defect tire under the warrantee. Not all 4.
Yes I would service both.
No I would not expect or demand the shop to foot the bill for the good side.
Most of the time I replace front and rear tires at the same time when the front is still good for 2-3000 more miles.
I'd better get of here. I actually have a new set of forks sitting on the bench I need to go install on my bike!
