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  • Writer's pictureKai

Clutch and Main Seal Job

Yes, you can trust after 30 years all your K bike engine seals are still pretty Ok and your clutch works like on its first day. But you better dont. So out with the old stuff and brand new components in.

Before we start, make sure your clutch components still have their assembly check marks! In most cases these marks are either white or yellow. If you´re uncertain these are still visible just set your own marks on all clutch cage components. These marks will help you during assembly once everything is replaced. Note: The clutch disc itself doesn´t need a mark.

Getting the clutch cage out can be a painful experience. In 99% of all cases the 3 splines attached to the flywheel are rusty and sticking in it real tight. There´s no real good tips here other than patience and slighty hammering on these using a rubber hammer. Make sure not to damage anything.

Two things to mention here. Upper left corner, this is the original check mark in yellow. Second, check the state of the thrust ring. It shouldn´t be too worn and with scratches.

Better life with tools. There´s DIY options having the thrust wheel in a fixed postion, I however recommend investing 10 bucks and purchase this tool. Just use the old bolts to attach it. With some elbow grease the center nut should come off easily. It´s tightened with 114NM so make sure creating a huge lever when opening it. Never ever hammer on it! Once the center nut is off, pull out a small rubber o-ring that´s holding the flywheel in place. You´re also good cutting it as we´re going for a new one anyways. It can´t be reused.

Not shown here but recommend putting the old center nut back on the shaft threat when pulling out the old seal. Just to prevent any damage to the threat when working. Also it´s beneficial heating up the area around the seal by 80 degrees celsius. Makes things easier...

Thoroughly clean and degrease everything. It should look like new afterwards.

Same goes for the clutch components. I am using Acetone to degrease and clean all components. Attention!!! Be sure you don´t remove your/the check marks during the process.

Another thing to mention; the center nut as well as the 6 screws holding all together MUST be renewed. These are one time components. Don´t even think about just using Locktite during assembly. Please go for new ones. Needless to say a new clutch disc makes sense, as well as new o-ring.

I´m certainly a tool addict, yes I am. There´s 3 methods getting the new main seal in. Number one, hammer it in. Hm, not really. Number two, hammer it in with a special tool. Well that works, however pressing in it using a special tool is our way getting it done.

Step one, put the seal in its postion.

Slip over the press tool. And just by the way, we´re working dry here all the time. There´s no need putting grease anywhere or heating things up. No grease, no heat!

By carefully turning the bolt the new seal is slowly and even pressed into its final position.

Et voila. The educated eye will notice the seal is exactly 1mm standing out. This is the desired final state.Remove the tool and open up a beer.

You still have your check marks, right? Good. Before putting the new center nut on, don´t forget putting in the new o-ring!!!!!! Just press it in with a dull tool. This can by anything not damaging it.

The new (!) center nut requires 2 steps. You want to torque with 140 NM first, then loose the nut again.

Second step is tighten it again with 110 NM. Did you notice we´re using our holding device again?

Let´s talk about MBU30 or better knows as "Staburags". You need to have this, simply. STABURAGS NBU 12 K is a proven rolling bearing grease for long-term and lifetime lubrication in medium-speed applications, e.g. in mechanical engineering, power plant technology and in the engine sector.

STABURAGS NBU 30 K can be used for long-term and lifetime lubrication in slow-running, highly loaded rolling and plain bearings, in applications in mechanical and plant engineering as well as in chemical and power plant engineering.

You will need to just a few grams on the thrust washer for a smoother shifting experience and of course the crankshaft teeth before putting on the flywheel. Don´t forget doing this!

Same goes for the friction surfaces. Just a very tiny bit of MBU30 on these as well. It´s optional, but I highly recommend putting some on the 3 splines as well so they don´t get stuck again.

You still have our check marks, right? :-) The clutch basket, watch out for the check marks and install with 120 degrees offset on these. Use a "Kupplungszentrierdorn" (clutch centering pin tool) getting all components centered and tighten the 6 new mounting bolts crosswise at 19 NM +2.

Job done! As always hoping you found this beneficial. Stay tuned and save.


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