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Discussion Starter · #1 ·
Guys,
I thought it might be helpful if I documented my Ninja 400 front fork rebuild. I had already removed the forks from the bike, and pulled them apart, when I thought of this, so sorry, I'll try to cover the highlights. Removing the forks was very straight forward. I had made a set of billet aluminum boss's that are screwed to the front frame sliders, so that I could support the bike, removing the front wheel & forks. See the photo. I have a bicycle frame vice that is real handy to hold the fork tubes during disassembly. Here are all the fork parts laid out in there correct order. The bike has 1850 miles on the clock. The left fork oil was clean & red in color, the right fork oil had what looked like Teflon bearing slider material in the oil. Both had very corroded circlips. The next step is soaking the aluminum lower sliders in my paint removing solution, then bead blasting. I'm chromating the lower sliders off gold color. It stops corrosion for good.
BMHS
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Discussion Starter · #3 ·
Guys,
I received the YSS Front Fork Upgrade Kit yesterday.
Here are some of the parts.
The PD valve - Race Tech calls it the emulator.
The adjustable top machined cap.
I measured the single rate YSS fork spring, against the Kaw. OEM dual rate fork spring. The data is very close, just a little heavier on the top.
I have all the parts ready to assemble, & I have all the instillation tools made, seals, etc., all I'm waiting for are the Teflon slider bushings from Kawasaki.
Brian (BMHS)

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Discussion Starter · #4 ·
Guys,
The Kawasaki Teflon slider bushings came in this afternoon. I got an extra spurt of energy, and decided to assemble the forks. Before I forget, I made a complete set for Ninja 400 fork tools for disassembly and reassembly. I'll shoot a photo of all the tools Saturday. If anyone wants the critical dimensions they can PM me. I assembled the forks with 20 wt. Motul racing fork oil, at 100mm as recommended in the YSS instructions, and I'll mount them back on the bike this weekend that way. But I have to tell you, the compression is way up. After I ride it, I may try a lower/thinner Motul fork oil, we'll see.
BMHS
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Discussion Starter · #5 ·
By the way, you know what was the hardest part of this job, removing & installing those DAM stone guards on the top of the fork sliders. Because they are not a round shape on the top side, it's almost impossible to push them down. What a pain.
Brian
 

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Discussion Starter · #6 ·
OK,
So, last night I finished the forks, with 20wt. oil. This morning, after breakfast I tested the forks one at a time, manually pushing them down. Not very scientific, but they hardly moved at all. So realizing that at this point, an oil change was very easy, I drained the forks, and replaced the 20 wt. Motul with 10 wt. Motul. Again, I did a very unscientific push test, and it seemed way better. So I mounted the forks back onto the bike, the wheel, & the fender. I torqued everything up, and went for a short chilly ride. The forks are way better than stock, braking is really improved, because the bike does not dive like it did before. The front ride is way better, but the back end with the GSXR 750 shock is WAY too stiff. I have the Ninja 400 YSS rear shock arriving next week, so that should solve that issue. I decided to purchase the YSS shock that had high & low speed compression adjustments. It was about $100.00 more, but I figured it was worth it.
BMHS

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