The Thread Spread - Revisited
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-Shocks Pass Gas-
Nitrogen Is So Cool
The question - I have an 88 LT250R, the stock rear gas shock seems real "soft". I am about the tighten up the spring by turning the big nut under the spring. What about the pressure in the gas bottle? The book doesn't mention anything about it. How much pressure should be in it? What kind of gas is in it? Is it just pressurized air?
The response - You can attempt to set the preload to match your weight and riding style but read on.... Typically the gas charge is around 350 psi, also typical is that it is nitrogen. Nitrogen is "more" inert than regular air, nitrogen won't hold as much moisture, nor is it as affected by temperature changes. That's why it's exclusively used in aircraft components(landing gear struts, accumulators, so on...)
When shocks start to get soft, it isn't always the charge in the res., but it is one cause. Has the shock ever been rebuilt?? The oil in
the shock begins to deteriorate with heat, from friction of internal parts, and age. It's one of those things that you really never notice how bad it is until you get it serviced and you say "WOW, did it ever ride rough before!!" I would consider sending the shock in to many of the reputable shock repair shops, Progressive, Denton Racing, Devol Racing, Shoc Connection, to name a few to have the shock rebuilt. It's worth the time and money. Could run you anywhere from $100 for a simple service to a total rebuild, revalve, long travel mod and spring for around $350. Good luck.
Backcountry
I would add that it's fairly easy to check the compression force in the shock as well (the result of the nitrogen pressure in the shock). Remove the shock from the bike. Remove the spring. The damper will be extended due to the pressure of the nitrogen in the shock (if there's any left). Get a bathroom scale. With the shock in your hands press it against the scale and measure how much force it takes to start the damper to compress. For a 86 TRX stock shock, that number is 51 to 85 lb. of pressure.
That's a simple way to do it, and there are better ways especially if you have a hydraulic - press. I usually do that before I take a shock apart so I can get an idea of what might be wrong before I start. Additionally I think that Outer Wears (the cloth shock covers) are a good idea because they prevent dings and dents to the shafts. If you have $1500 (like many of us do) into shocks on your quad - it's worth it. They weight almost nothing.
Rick
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