BMW K bikes (Bricks)

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roys

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Hi,

Last week I replaced the rear shock on my 1987 K100 base for a YSS shock. The difference in handling is amazing - it is much more precise, especially coming out of corners under power. I am still playing around with the rebound.

I also bought “hyperpro” progressive springs but have no idea how to change the existing ones with the new ones. I want to do all the work myself but do not know how.

So I am looking for instructions /links (hopefully with pictures) fit for a naïve mechanic.

Thank you,
Roy

    

phil_mars

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Hi Roy, I am sure you will get more information from other members who have done this, and I am interested to see how this turns out. Hopefully you have some information with the springs regarding fork oil levels and spacers. I am quite sure it can all be done in situ but removing the handlebars and maybe guages should give you plenty of clearance. Draining the fork oil should be reasonably straight forward and once that is done it is important to support the front of the bike so there is no compression on the front springs. Once you have removed the black caps on top of the forks you should be able to remove the filler plugs and washers. The next bit is the one that makes me nervous which is removing the ring which holds the top plug in. Hopefully if the springs are old and there is no pressure on them there should be no risk of parts flying off. The manual shows the clip being removed with the forks out of the bike but the best system I have seen leaves the forks in the triple clamps and a two jawed bearing puller used to depress the top plug so that the clip can be eased out. Once out slowly releasing pressure on the bearing puller should allow the top plug to come out but if it is sticky the manual suggests installing a bolt into the filler hole and pulling it out. The rest should be reasonably self explanatory and I also found this website: http://www.k11og.org/tech/k11tech_springs_install.shtml which should also point you in the right direction even though it won't be exactly the same it should not be that different either. Hope this is of some help and with advise from other members it should be relatively painless. Looking forward to the end result.
Regards,
Phil

    

roys

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Hi Phil.

Thank you for your answer and link.

The “hyperpro” instructions say 190CC of 20w oil – which is less by volume and more by weight then stock.

I have read your answer and the link carefully and have a few questions.

1) Supporting the bike: Do you agree that just putting engine on wooden block + central stand are not enough as bike can drop – so I better get something to tie bike on both sides?
2) I did not understand all the English in the article, why is the string needed? I have found this definition “Machine screws differ from simple screws in that they fit into a female receiver, which may be a nut or a pre-drilled hole, instead of into a soft material like wood” , however I do not understand what they are saying there?
3) Do I understand correctly that your advice of using “two jawed bearing puller” is (a very good) replacement for this part:
“5) Push down on retainer cap with 2 Philips screwdrivers to allow the dogs to be removed Take the bike off the center stand and be sure to have someone holding it from the rear. Keep the side stand down so if the bike-holder loses balance he can sway the bike to the left and keep it from going over. There are four holes in the retainer cap. Insert the tips of two large, long-handled philips screwdrivers into two opposing holes and, standing on the pegs, push down. Simultaneously your two helpers must be busy, the first steadying the bike and the second pulling on the string. The aim is to push the retaining cap down on the rod so that the pressure on the dogs from the cap recess is removed and the dogs can be removed from the slot on the rod.”

Thank you,
Roy

    

phil_mars

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Sorry Roy I think the link needs to be taken as a rough guide as I too was a bit confused with the procedure they used. In typical fashion it is similar to the K100 but sufficiently different to make it confusing.
1)When I took my forks out to change fork seals etc it was supported on the centre stand and a block under the engine and was quite secure but one can never be too careful so extra security would not go astray.
2)The two jawed puller idea came from another article and to me seems better than trying to push down with a couple of screwdrivers and remove the clip at the same time. As the clip at the top of the forks is not a true circlip the bearing puller should allow safe removal especially if you are doing it alone. Essentially once the clip has been removed the plug should come out as you release pressure on the puller but if not a bolt in the filler hole will allow you to pull it out but in my limited experience the plug is usually under a bit of spring pressure. It is possible to top bolt on the triple clamp may need to be loosened but I am not convinced that it would put any pressure on the plug.
4) The weight and volume of oil seems a bit odd and as I mentioned some time ago may need to be experimented with, but if the spring is significantly longer than stock it would explain the reduced volume but a large increase in the weight usually involves modifying the valves but I would suggest confirmation from other members on that point. I hope this answers more questions than it raises but also do a Google search on front spring replacement and even though all bikes are different the procedure is essentially the same and it should put you on the right track.

Regards,

Phil

    

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