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Going through the 3 sets of forks I got to cherry pick the fork rebuild. Cb400f front forks.... One set has nice lowers but the tubes definitely peeled a bit of chrome 1 inch above the fork seal to show the nickel.. The other set looks better but has small pits throughout but nothing more than a pin tip in size. Maybe a tiny swish scratch down low but nothing that got to the nickel layer. This set is nice because it has pre-load adjusters up top. The third set is yuck. I'm planning on building a nice set out the two of the better ones.

Question is.... How do i know if there is too much pitting?
 

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Years ago I made up a fixture out of a 16" piece of 2x4 and four 8mm skate bearings (2 at each end of the 2x4) so I could set a fork tube down on the bearings and turn the tube for inspection.

When I got my CM400C the tubes were a little pitted and under magnification there was red rust in the pits. I cleaned them up with 400 then 600 grit wet-dry paper and WD-40. Never had an issue with them after that.
 

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You'll know if there's too much pitting if the seals leak after you've reassembled the whole thing.
You have several options, New tubes, my preferred choice, you know where you are this way, but relatively expensive, Or you could get the Old tubes rechromed, also not cheap, but they will be straightened if bent, chromed and reground and polished,
Or you could sand your tubes to remove rust, fill any pits with epoxy and sand again til smooth. The rubber seals will last for a week or so before you need to replace them again, and the fork oil will need cleaning from your tyres.....
 

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Several times I have saved fork tubes that had pitting. Sure you can rechrome them or find better ones, but for some of these old bikes it's just not worth it. The way I do it is to use a pick, like a dental pick, and get any rust out of the pits. Then I clean the tubes thoroughly with lacquer thinner. Then I fill the pits in with JB Weld epoxy. After it's set for a day, I sand it smooth, usually starting with 320 grit paper and working up to 1000 grit. Then I polish with a cloth and Mother's Aluminum polish. Any metal polish will do, they are all just a fine abrasive. I have never had a seal get trashed prematurely on one of these fork legs. They seem to work just fine. Afterwards, I can run my fingers along the tube and feel no irregularities at all. If you start off with something in horrific shape your outcome might not be as good. However, I have done this on some pretty ugly tubes. It's worth a try, since you will only be out for the cost of sandpaper, a set of seals, and a few hours of work.
 
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