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Discussion Starter · #1 ·

This is my first post here. I tried to search for a similar topic but didn’t find what I needed.

My issue:

I own a 2008 ZX-10r with stock Kayaba front fork.

When I bought the bike, it had Ohlins springs and the fork was compressing very hard and too little.
I don’t know what oil was used.
Yes. It was a track bike.

In a 300km road trip I “managed” to damage the stearing bearings.

At that time I also had a 2007 cbr1000rr from an accident but with the fork in great condition (undamaged) so I took the springs from the cbr1000rr, measured them (they were a little smaller then the Ohlins springs that I took out from the ZX10r). So I made on a CNC 2 bushings made of teflon to compensate for the difference.
Put the fork back together and it worked like a charm.
The front suspension was working perfectly after some small adjustments.

Now, after 2 seasons (road trips only), a weird noise started to “appear”.

I’m 100% sure that the bushings that I made and put inside the fork are the reason.
I verified the stearing bearings and there are no noises coming from there. Also steering is like it should be.

Now... the questions:

I want to replace the DIY “fix” that I made and put some new springs with new oil and new seals.
The problem is that I don’t know what to buy.
The options are: Stock (OEM), Ohlins, Bitubo.
Also, as far as I searched in the manual, I should be using 0w or 2.5w fork oil.
Do you have any sugestions?

I have 68kg. I ride my bike only on the road and sometimes on the twisties (canyons).

I live in a city with very bad roads (lots of potholes).
I never ride with passenger. I tend to brake hard with the front. => don’t want a very stiff front suspension but also not a very soft one.

Before you judge:
1. I had to use the springs from the cbr because I had no option at that time.
2. I’m thinking about ohlins springs again because I don’t know what ohlins springs the previous owner used (he has 90+ kg).
3. Also I don’t know what settings, what oil and what quantities of oil were used before. This time I want to service the fork respecting the manual.

Thank you very much for your time and hope somebody will be able to help me to get rid of the weird noise.

PS: the noise sounds like a “click” and it’s not easily identified as a “metal noise”. Sometimes sounds groove, otherwise sounds like a cracking plastic.
I’m 90% sure the noise is coming from the forks (not the brake discs / brake pads / other plastic components).

Thank you! All the best!

1,529 Posts
Couple specs for you.

Stock spring rate in a 2008-2010 is 9.8NM. Also the 2007 CBR1000RR stock spring rate is 8.8NM.

Ktech makes a direct drop in fork spring, part number 38-235-XX and go from 9.0NM up to 11.0NM in .5 increments.

Bitubo makes direct drop ins. Part number MK35 - .9 kg, MK73 - 1.0 kg, MK36 - 1.1kg.

As far as I can tell. Ohlins drop ins only come in 10.0 nm springs (basically stock).

So if you wanted to keep the feel the same via spring rate, I'd get the Bitubo MK35 -.9kg (same rate as the CBR) or the K-Tech springs in a 9.0NM (38-235-90).

The Kawi manual wants you to use KHL-15-10 at 107mm air gap. This equates to 15.30 CST @ 40c. You want to go with as close to CST 15.30 to get the best damping curve. If you were in my shop I would recommend the following

Maxima Racing Fork Fluid 5wt (16.20 cst)
Motul Full Synthetic Very Light Fluid 2.5wt (15.00 cst)
Silkolene RSF Fluid 2.5wt /0w-20 (13.60 cst)

Any of the the other fluids will work fine for what you're trying to do, the three above is what I carry in my shop. Pretty much any manufacture will post the CST on their website so you can figure out what to use.
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