SR 650 Fork Rebuild Tips

Forks are a somewhat simple yet mysterious device. They can be tricky to take apart and put back together without the special tools the Kawasaki manual shows are needed. However, thanks to some tips gleaned from the KZRider Forum, this job was made easier.

Fork disassembly tips

Disassembly of my fork was done with the assistance of a mechanic friend. We first tried getting the allen bolt out using an air impact tool. Once the bolt loosened a bit the damper rod just spun so some way of holding the rod was needed. The mechanic pieced several socket extensions together and a 3/8" extension pushed into the top of the damper rod held it so the allen bolt could be removed.

Looking at the damper rod, the top end is shaped like a 12 point socket:


So I went to the local farm supply store with the damper rod in hand and bought a M10x50 bolt and matching nut. The head of the bolt fits a 17mm socket. Other Kawasaki models are said to use a bolt that fits a 19mm socket. The size of the damper rod is dependent on the fork tube diameter so the required bolt size will vary.

Here is the bolt in the damper rod:


and a closeup of the welded nut:


Before reassembling the damper rod into the fork tube I applied a thin layer of lithium grease to the fiber ring on the top end of the damper rod. This will help the rod slide down into the fork tube as there is a step where the fork tube gets smaller about 1/3 of the way to the bottom. The Kawasaki service manual says a special tool is needed to compress this ring first which may be needed if a new fiber ring is installed. Mine was in good condition so I didn't replace it. Traces of the grease can be seen in the photos above.

To hold the damper rod while torquing the allen bolt I assembled a collection of 3/8" drive extensions to reach through the fork tube:


I put the damper rod into the fork tube and gently worked it past the step in the fork tube. With the extensions in the fork tube I placed it upside down on the bench and placed the valve pieces on the end of the damper rod:


Note that I had used enough extensions so that when the slider and fork tube were fully mated, the extension would protrude from the fork tube. They were still short enough so that the fork tube could rest on the bench while the extensions held the damper rod far enough out to start the allen bolt.

I applied a thin layer of grease on the lips of the new oil seal before placing the slider on the fork tube. I then put the slider in place and started the allen bolt. Once the bolt was started I pushed the slider completely onto the fork tube and placed the assembly horizontal on the bench being careful that the valve pieces didn't become seperated. I torqued the allen bolt to 16 ft/lbs per the Kawasaki service manual.

Seal and oil replacement

To remove the seal from the slider I purchased a seal extractor. This tool looks something like a medieval battle axe. The head is curved and has a hook at either end. To use it simply use whichever hook provides the best leverage to hook under the metal ring of the seal and pop it out. The keep from damaging the soft aluminum of the slider I used a thin piece of wood as a cushion under the extractor.

To drive in the new seal I used a light coating of grease around the edge of the seal and then used a large socket as a driver to keep from deforming the seal. Once it was in place I reinstalled the washer and snap ring and assembled the slider onto the fork tube holding the damper rod as described above.

I had purchased a quantity of 10 wt fork oil before I bought the factory service manual which called for 15 wt. So far I haven't noticed any real problems, but I will probably used 15 wt when I change the fork oil next year.

To fill the forks with oil and meter it out, I purchased a feeding syringe from the local veterinary supply store capable of holding 60 cc. A 4mm hose fit over the end very well and I was able to suck the oil out of the bottle, remove the hose, and then squirt the oil into the tube without messy spills. Being able to accurately meter the oil in 50, 10, 5, or 1 cc increments proved invaluable.

To measure the fork oil level I had a fiberglass rod that I borrowed from one of my amateur radio antennas that is about three feet long and a quarter inch in diameter. Since the fork spring must be in the fork to measure the oil and since it protrudes out the top of the fork about 2 cm or so, I made marks on the rod that corresponded to the top of the spring, top of the fork tube, and the desired oil level.

Finally, my fork tube with the leaky seal had some rust pitting in it including the seal swept area. Upon recommendation from one of the KZRider members, I used 400 and 1500 grit sand paper to smooth the pits and then polished the tube with Eagle One's Never Dull. So far the tube is smooth to the touch and time will tell how long the new seal will last. In the mean time, this bike is a blast to ride.

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Original content Copyright © 2004-2023 Nate Bargmann
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This page last modified
February 13, 2005
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