The next question would be are you using stock fork springs? This is critical because the aftermarket fork springs will affect the volume of oil to be replaced. Complete disassembly is also need for the correct oil volume. Were the forks 100% disassembled and were the bushings checked for spec? Assuming they were in spec. This is assuming that the forks were disassembled and reassembled properly. First thing to me it sounds like there is too much oil in the forks and not enough air space. So looking at this thread you now have a chatter issue with the rebound. The springs do a couple of things, they set the ride height of the bike (sag) and the provide rebound force to bring the bike back to ride height. To heavy of oil and the dampening will be slowed to the point where the suspension is very stiff, and the rebound is slow. I would highly doubt that the oil over 15 years would make a notable increase in orifice sizes. The orifices’ that are in the working mechanisms of the forks are designed to have a certain viscosity of oil flow through them. The specifications give you no linear measurement of the air space so what is the standard to use?įork oil weight. In my opinion volume is the better method for measuring oil. Too much oil and the ride will be hard to little it will be mushy.

I am not an expert by any means but I have done several forks and much research in to this topic.įork oil level and airspace are critical to the dampening process of the forks. Boy there sounds like a lot of things going on here.įirst of all the fork suspension on a stock ST1100 is very soft, almost to the point on a 15 year old bike where it does need some upgrades especially if you do any hard cornering.

Honda st1100 fork oil viscosity chart