YB 100 forks

[nerabus 7932]

Just wanted to post a bit about Yamaha YB 100 fork overhaul - some discussion on this forum years ago about this. Wisdom of the time which I've seen in advice with other simple small bikes is 'take out circlip and use fork as slide hammer to knock fork seal out'. If your forks are rusty/corroded this won't work because the wee top hat thing inside the fork slider will break and scar the fork stanchion before the seal will come out... Morale is 'don't use brute force until you've decided which bit you're willing to sacrifice/have a spare for'. I had two sets forks, one with ruined stanchions and one with ruined sliders. I sawed up the sliders to save the stanchions in one, and hauled out the stanchions and seals, destroying them in the process in the other. The only way I can think of getting them out if you don't have two sets is to push the fork stanchion in as far as possible and hold it there with cable ties or something then drill through the seal in lots of places so you can prise it out. Pushing the stanchion in means that if you do nick it while drilling, at least the damage is well up the stanchion and you can fix it with the old fashioned Araldite filling cure! Cheers, And
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he who laughs last has not yet heard the terrible news

[stinkwheel]

Even if you do get them out, the area on the fork bottoms where the seal seats gets so corroded the new seal doesn't seal up.

The only solution is to either replace it or have it machined out round again then fit either an oversize seal or sweat a bushing in to take it back down to the original size.

Drilling the seal doesn't really work, it's got a spring steel insert in it that's almost impossible to drill.

I got mine out by roasting the rubber away with a blowlamp then clamping the fork in a vice and violently slide-hammering them out. Then found the new seal wouldn't fit and there was no groove left for the spring clip anyway.

If there is a lot of corrosion round the seals, the forks are essentially scrap without doing some fairly heavy duty machining anmd spending three figures on parts to sort them out again.
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.