this is a question that has been asked a few times lately. i have never even opened up my forks yet, but i do want to change out my oil. so do i just open the fuckers up and dump out the old oil? and when i put new oil in how do i measure it? i know its measured by how far from the top of the tube is empty, but thats about all i know.

when I did mine recently, we used the depth gauge on a vernier

Fork oil should be changed two to three times per season, with a complete rebiuld each year. To change the oil on a 750 or 1000 and 04 600's you will need a spring compressor to remove the springs. After that you can just turn the fork upside down and pump out the cartridge. Then refill the fork with the proper oil and bleed the cartridge by pumping the damper rod again until all the air is removed. To set the oil level I use a Mighty Vac to remove the excess oil. Just set a zip tie at the level you want and pump the Mighty Vac until it slurps. If you want I can get several tools for the job ranging from $30 to $100. Then just reassemble the forks and reinstall according to your manual. Normal range for oil level is 90-150mm, we set our starting at 130mm.

When checking oil height, do you leave the rod that holds the valving all the way down? Also, do you guys leave the rod that controls the rebound damping in or out?

GMDBoston said:
Normal range for oil level is 90-150mm, we set our starting at 130mm.



Peter, how does lowering the oil height affect things?

I just put new springs in my SV1000S (racetech .90kg) and set the oil level to the stock height according to the factory manual (162 mm). Should I be running a lower height?

Hopefully you can answer this before you leave for Loudon. If not, I'll ask you up there and quickly adjust things.

When the forks compress while under braking and bumps they are more likely to bottom out if the oil level is lower. You have a volume of air and oil in the forks. Oil doesn't compress very well. Air does to a point. Obviously we are all looking for an oil level that will allow the forks to use as much travel as possible. The more air (lower oil level) the more travel that will be used. The hard part is finding that perfect setup without ending up on you're head.

It's easy to add oil, harder to remove it.

I would start at 130mm, It works great on most bikes. 162 is to low for racing.

Philbie said:
When the forks compress while under braking and bumps they are more likely to bottom out if the oil level is lower. You have a volume of air and oil in the forks. Oil doesn't compress very well. Air does to a point. Obviously we are all looking for an oil level that will allow the forks to use as much travel as possible. The more air (lower oil level) the more travel that will be used. The hard part is finding that perfect setup without ending up on you're head.

It's easy to add oil, harder to remove it.



The air gap is a secondary spring in the fork. It is an exponentially progressive spring ( presure increases with the square of volume). A lower oil level gives a softer and less progressive air spring and vise-versa. Oil level has the greatest effect on bottoming control. How ever if your oil level is very high, say less tham 100mm I would try a stiffer fork spring and if you don't bottom with less than 150mm oil level try a softer fork spring. Compression damping plays a major role as well, but is much harder to describe on a key board. See me at the track or in the shop so can feel the suspension and I can tell if the damping is too firm or too soft.

Philbie said:
When checking oil height, do you leave the rod that holds the valving all the way down? Also, do you guys leave the rod that controls the rebound damping in or out?




Metering rods in, damper rod all the way down.

GMDBoston said:

Philbie said:
When the forks compress while under braking and bumps they are more likely to bottom out if the oil level is lower. You have a volume of air and oil in the forks. Oil doesn't compress very well. Air does to a point. Obviously we are all looking for an oil level that will allow the forks to use as much travel as possible. The more air (lower oil level) the more travel that will be used. The hard part is finding that perfect setup without ending up on you're head.

It's easy to add oil, harder to remove it.



The air gap is a secondary spring in the fork. It is an exponentially progressive spring ( presure increases with the square of volume). A lower oil level gives a softer and less progressive air spring and vise-versa. Oil level has the greatest effect on bottoming control. How ever if your oil level is very high, say less tham 100mm I would try a stiffer fork spring and if you don't bottom with less than 150mm oil level try a softer fork spring. Compression damping plays a major role as well, but is much harder to describe on a key board. See me at the track or in the shop so can feel the suspension and I can tell if the damping is too firm or too soft.



Thanks for clearing up the measurement of the oil level. I'd love to stop by but it's one hell of a commute from Phoenix http://www.gixxer.com/forums/images/graemlins/laugh.gif. If you do anything in the midwest I'm planning on running Mid-America over the 4th of July. Family in that area and it's a good reason to see them and race at the same time.

does someone knows if the level is the same for a 1000 k3 than k1 or k2 ?

I'm new to all this but I just talked to a race tech tech and he said on my bike ('02GSXR600) to use 5weight oil at a height of 110mm air space with no spring fully compressed. I just ogt off the horn with him 3-4 hours ago. My buddy used to race 250GPs in Europe so he is doing all the work for me but I want to at lease know what he is doing. Hope that help some one out.

Jarrod