Dave's Saggy Shock
I've got an '03 GSX-R1000 with a bit over 14K miles on it. The shock has started feeling a little mushy, and I'd like to get it back to how it felt originally. I remember reading that a shock would typically need to be rebuilt at around 15K miles. I've also heard that simply changing the fluid in the shock should restore its prior performance. Unless this is something that can be done by your average shade-tree mechanic, I'm probably going to just remove the shock myself and have someone else do the work on it.
On a side note, my forks still feel great. I had the seals changed about a thousand miles back because one of them was leaking, during which time the fluid was also changed. So did changing the fork fluid do the trick for keeping the forks in good-performing shape, or should I expect to have to perform some refresher maintenance on them in the future?
I'm basically looking to get back to the status quo while keeping the budget as reasonable as possible. What do you guys recommend?
via SR Mail
Your shock can be returned to almost its full original functionality with some fresh fluid, but "your average shade-tree mechanic" doesn't have the tools for the job-specifically a way to recharge the shock with nitrogen. It's easier-and safer-to take your shock to a dealer or suspension shop and have the work done by a professional, who will disassemble and inspect the internals, refill the shock with fresh fluid, assemble it properly with no air inside and charge it with nitrogen to the correct pressure.
Your forks, with fresh fluid from the seal replacement, should be fine for a few thousand more miles. Inside your fork and shock are bushings and seals that wear over time, compromising their performance. We recently had the suspension rebuilt on an '03 GSX-R1000 ("New vs. Old," Aug. '07), and in that bike the internals all seemed to be in good shape. As with your shock, however, it would be a good idea to have a professional look inside your forks at some point to ensure everything is in working order, either next time a seal is replaced or if you notice performance degrading.
Be Careful What You Ask For
I have an '07 CBR600RR and live at 4100 feet of elevation. How much horsepower am I losing at this altitude, and would a Power Commander solve this horsepower-loss problem? What say you, o enlightened one?
Klamath Falls, OR
Internal-combustion engines lose horsepower with altitude because of the reduced air pressure. Our '07 CBR600RR made 105 horsepower on our SuperFlow CycleDyn, a number that has been corrected to sea level using an SAE (Society of Automotive Engineers) correction factor. Air pressure at sea level is around 30 in. Hg and decreases to approximately 25.8 in. Hg at your altitude. Using the SAE correction factor, our 105-horsepower CBR loses close to 15 percent of its power and would read about 90 horsepower-uncorrected-on a dyno at that altitude.
Your CBR, like most current fuel-injected bikes, uses a manifold air-pressure sensor that detects the change in pressure and adjusts the fueling accordingly. Adding a Power Commander or other fuel-injection tuning tool may gain you some power, but not because it's correcting the system for the higher altitude-that has already been done for you.