Fork Oil?

^^^
I weigh 150 and Ken did all he could to my front/rear '03 stock suspension to make it work for me.
Save some money and get a FPU kit put there for your weight...huge difference more me.

 

Changing oil isn't a big deal (aka cheap) and the recommendation is at the beginning of the year and mid season. You'd be surprised how nasty it gets in a relatively short time.

 

How many TD's do you do per yr? I would say that you should talk to a suspension guy. It may vary depending on how many days you do <5 or >6 may make a diff.

 

Quick question: do you disassemble the whole fork, take out the spring/cartridge, and refill to spec or just crack open the top, dump out the fluid in a measuring cup, and add what came out?

 

With my Ohlins cartridges by the time get the forks off and top cap loosened it's two more steps to remove and clean everything (remove spring, unbolt cartridge from lower).

 

I would say you should be doing it AT LEAST 1x/yr since you do that many (must be nice :thumb I hear you about not wanting to upgrade the suspension on a older high mileage machine so frequent fluid changes and inspection will be a great bet for now. If you plan to upgrade in the future save all the pennies you can and get a track ready weapon!.. Did Ken recommend any revalving or springs etc.?

 

If your fluid is old, you should disssemble everything and clean it. If its not too dirty you can do a "pump and dump" or fluid only. I have mine changed about twice a year, disassembling and cleaning everything once a year. Some super meticulous racers change the fluid every couple weekends. It turns black after about a day of use...

 

hmmm. My first track day was on my 05 R1 with 48,000 miles. 100% bone stock, just regular maintenance. It is now my dedicated track bike so I don't put a lot of "soft" miles on it anymore. If your gixxer was well taken care of, 25k miles is not that much.

 

Wow, very informative thread. I'll be honest and say I have never had the oil in my stock forks changed; they never leaked and it never crossed my mind. I bought my bike in 2009 and have put somewhere in the range of 20K+ miles on it. I keep up with other maintenance! I'll make sure it gets done before the start of the season.

 

Just as another piece of the puzzle - fork oil is changed because of contamination, but also because of viscosity loss.

Many of you know this, but for those who don't: Forks work by regulating spring rate (damping) with oil flow. The oil passes through orifices in the valving that controls how fast the fork can compress or rebound. When the oil loses viscosity, the valves do not function as designed because the fluid is "thinner", and you lose damping characteristics.

There are articles/discussions over how fast fork oil loses viscosity, but I am of the mindset that forks should be done rather frequently. I do mine about 3-4 times a year, but I am also at the track regularly. An average of every six weekends would be good... more is better.

 

Agreed, it might be efficient to have a lower mile chassis and engine for racing, but a well maintained bike for the pleasure of track days will do just fine. My 750 has 22k and is now a dedicated track bike as well - still rides as great as when I bought her with 6k on the tach.

 

If you changed the oil & cleaned the fork internals a fluid change would be good. A proper cleaning & oil change would be better.

Some years I ride a lot between racing and track days and so on I try to get a fluid change mid year also.

You might be surprised how much stuff can wear out in a set of forks. Even stock forks need service. There are bushing and valve shims that wear out. For the stock forks to work these things need to be inspected. Not sure if it's worth the cost to have a proper rebuild on a bike you plan on trading in a year or so. They would work much better with a proper refresh thou.

 

Straight from the Ohlins website
http://www.ohlinsusa.com/ohlins-usa-why-service

"Why Service?

Just as you regularly change the oil in your engine, the oil in your suspension needs to be changed as well. Worse yet, your suspension doesn't have a filter!

With each stroke of travel, the polished surfaces of your suspension pick up microscopic particles of debris. Those particles get drawn into the oil, and over time contaminate the interior passageways. As the miles accumulate, so does the grunge. Without regular service, your high-performance suspension begins to lose it's ability to dampen force.

To keep your investment performing at it's design level, Ohlins recommends servicing your street motorcycle suspension every 12,000 to 15,000 miles, and your track/race bike suspension every 10 hours of track time."

10hrs seems like a short interval but I'm guessing that's for the fast racer types.
I don't do mine at 10hrs but would rarely let my suspension parts hit 20hrs without a full cleaning. I do it twice a year spring and mid season if I'm running one bike all season. You should see how dirty the oil is

 

I'm not a suspension expert I just play one on TV so here goes.

If you can get a proper shop manual for your bike it will tell you what bushing to check and what to look for. On my street bikes that I do this on, they will have bare copper showing if the coatings are worn off.
As for valve shim inspection, I believe older forks have a different styles of flow control vs shim stacks, but don't quote me on that. Shims that are worn out will need to be inspected by someone that knows what they are looking at. They are basically thin washers that deflect/bend slightly to allow fluid to pass. Over time they get thinner from rubbing against each other and then deflect too easy or take a set (think bent). Then flow control is being lost.
If you want to just compensate for too bouncy, go up a weight or 2 in the fork oil. If the bike calls for 5weight get 7.5 or 10 weight. I know some SV racers that use 20wt oil in the forks cause they have to use the stock forks for the class they race.