I have a new to me 2007 kls250 and was looking through the repair manual when I saw it recommends changing the oil in the front and rear suspensions every year. The instructions in the manual seem pretty involved, injecting nitrogen for instance. Is this something that can be done by a reasonably diyer or should it be taken in? Also, every year???

 

AZR, I think the rear shock is easier to work on than the fork. That issue of nitrogen...or air...is done at the end of the rebuild through the normal schrader valve on the piggyback. You're just pumping up a rubber bladder in the piggyback that works against the damper oil in the shock for tuning. It has some effect throughout the stroke of the shock but especially toward the end of stroke and bottomout. I use air instead of nitrogen which works fine for me, as I don't hammer the bike relentlessly, non-stop, for an hour or more at a time. I ride decently hard but letting up occasionally, stopping to take in the scenery or a pic, or the fact that the terrain isn't a constant hammerfest like a supercross track. Dealing with extreme heat for decent periods of time is the only advantage of nitrogen over air in our shock. Air is already about 80% nitrogen. That said, after you rebuild the shock it is quite easy to go to a shop and have them charge the bladder from their usually available nitrogen tank.

If you rebuild it or have someone else do it, it's probably worth replacing the main seal at the shaft with a new one instead of just dumping the old oil. And it's probably a good idea to use the main seal from KYB, as I feel it's the best quality. I tried an All ***** unit...also marketed by Moose and MSR...and it lasted about a month. There have been similar results from others.

 

The 2009 manual says you need to inspect the shocks for leaks yearly or every 7500 miles, whichever comes first. As long as you aren't leaking any oil or having problems with the suspension, I wouldn't think it needs to be changed very often. My oil is 3 years running with no immediate plans to change it in the near future.

 

I checked with the original owner and he had never changed either. There doesn't appear to be any leaks or issues with either shock. It's getting to be around 5 or 6 years old and only has around 2600 miles, all pretty light stuff. I'm a pretty conservative rider, no jumping around or seeing how fast I can hit the next bump in the road. Should I hold off or would the rebuild be advisable?

 

I agree with TNC that under non-competitive circumstances, nitrogen gives no real advantage over air. *

The other justification I often hear for nitrogen pressurization of suspension components however is that it supposedly evacuates at a slower rate than air. *This is something that my observations do not corroborate with but none-the-less may be worth considering.

It's also been my general experience that under non-competitive circumstances, rear shocks are prone more to age-related failure rather than mileage-related. This is where I'd tend to agree with NDKLX's break/fix strategy for rear shocks.

Front or rear, you'll usually get plenty of early warning on suspension leaks before the problem becomes catastrophic, so I wouldn't make practice out of an annual shock rebuild if the symptoms of a leak are not apparent.

 

Yeah, I think there may some truth about nitrogen not losing its molecules as compared to plain air, but I think it's more applicable to tires or other items where you have a microscopic porosity on a larger level. The great thing about using air is that you can use an inexpensive bicycle shock pump...that's shock pump not bicycle tire pump...to check and maintain proper piggyback/bladder pressure in the shock. As nitrogen pressure drops, the shock becomes more akin to an old school emulsion shock.

 

I just assumed they want you to use nitrogen because it would have less pressure change when the shock heated up/cooled down.

 

That's the main one...a more stable gas for wide temperature fluctuations.

 

And there won't be any moisture in the nitrogen as compared to air. The shock can get hot enough to turn the moisture to steam, which expands and increases the internal pressure.

Ride on
Brewster

 

AZR..you ever hear the old saying "IF IT AIN'T BROKE,DON'T FIX IT".If you have no problems with the suspension and your not trying to upgrade you don't really need to worry about it.Unless you see a leak or the suspension seems to be getting weak(sagging).Theres alot of maintainance that the book would have you doing if we were all Elmer J Fudd and owned mansions and yacths,but most of us aren't.Deal with the regular stuff,oil/filter/tires.Unless you start MX the bike then you can spend all that money on replacing and rebuilding everything the manual says.Get out and RIDE dude.