leaking fork

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mcollett
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My Bike: zxr400 l2
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leaking fork

Post by mcollett » Sat Jul 12, 2014 9:17 pm

front right fork is leaking from around the dust cover, i'm guessing the seal has gone.
Obviously both sides will need the seals changing, and i will be using the genuine seals from probably Corby Kawasaki.
Any ideas on the part numbers i need, and how difficult are they to change. Never taken forks apart but am mechanically minded with the help of my dad, a long time engineer.
Thanks for any help given.

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CaNsA
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Re: leaking fork

Post by CaNsA » Sat Jul 12, 2014 10:17 pm

The microfiche has the fork seals.
http://www.zxrworld.co.uk/zxr400/lmicro.html

Read this
http://www.zxrworld.co.uk/zxr400/forks.html

All this, and more is available on the main page
http://www.zxrworld.co.uk/zxr400/main.htm
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Ewetea
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Re: leaking fork

Post by Ewetea » Tue Jul 15, 2014 10:12 am

I will post my observations on changing the seals and you can make up your own mind.
You need to devise a method of holding the bike in the air while you remove the forks - you can't do one side at a time! I bought a cheap block and tackle to hang the front end of the bike from a garage roof support.
It's messy. The damper will contain oil that will squirt everywhere when you remove it.
Once the dust seal and spring clip have been removed from the sleeve, the forks need to be dismantled by holding the sleeve and yanking the stanchion away from it. There is a sliding bush on the stanchion internally, and another bush in the sleeve. The upper impacts on the lower, which in turn drives out the oil seal. The overlap of these two bushes is minimal, something like half a millimetre on the diameter. Thus, with wear on both items, it is possible for the upper to slide inside the lower which just jams the assembly and the seal does not move. I have stripped and rebuilt eight forks, and two of them jammed. The only way I could see to overcome the problem was to remove the bottom slider on the stanchion and push it up through the seal and out the top of the sleeve. The seal could then be knocked out with a long drift. To remove the bottom slider you will need a very small torx bit to unfasten the grubscrew. You must then heat the slider to break the grip of the loctite on the threads between slider and stanchion. I resorted to cooking it on the gas hob to achieve the result. This does mean that the paint will be destroyed, but you can repair that damage. You will need to use Loctite 636 when reassembling to ensure that no oil leaks up past the threads, and also take out any slack in the threads to prevent rocking of the stanchion in the slider.
When dismantling and reassembling the forks I used an old lower fork yoke securely clamped in a substantial vice, so that the fork leg could be clamped in the yoke. This ensured that it was held tightly with a circumferential grip. It also permitted me to put the spindle through the lower slider and yank on it to shift the stanchion from the sleeve. When reassembling, this arrangement also permitted me to compress the spring sufficiently to install the capscrew in the bottom of the damper, by pushing against the slider, the vice preventing any movement of the upper sleeve.
I invested in a slide hammer to install the seals since I knew that I would use it several times. It takes 10 seconds of hammering to fit the seal, and ensures that there is no damage to the chrome stanchion. Tapping the seal in with a drift does mean that it is not being fitted squarely, but will "rock" it's way in. It is a tight fit (to prevent oil leakage), so a substantial thump from the hammer will be required to move it. You only have to hit the stanchion once to wreck it.
To install the correct amount of oil I use a 50ml syringe from the chemist.
Since you and your dad are engineers you should be able to overcome any snags, and hopefully you will complete the job in an afternoon and wonder why I made such a fuss!!

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mcollett
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Re: leaking fork

Post by mcollett » Thu Jul 17, 2014 4:57 pm

Normally I would undergo any repairs needed. However I start a new job Monday and need the bike to get to and from, the the forks have been removed by myself and taken to a local bike mechanic for him to deal with them. Also needed new tires so the wheels went as well, this has saved me an hour or 2 in Labour charges... Although the bike is now on axle stands on the rear and suspened from the ceiling at the front. Should have the forks and wheels back tomorrow, rebuild Saturday with new brake pads while I'm there, then bed it all in on Sunday. :excited

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CaNsA
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Re: leaking fork

Post by CaNsA » Thu Jul 17, 2014 6:12 pm

Clean all that you can while the front and rear are open for access :D
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Re: leaking fork

Post by banner001 » Thu Jul 17, 2014 8:32 pm

Good time to re-grease headstock bearings, replace brake pads and fully clean calipers.
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