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Rebuilding 450 K4 Fork Questions & How to read a metric mic

3755 Views 15 Replies 7 Participants Last post by  danWI
I don't think I'm an idiot but sometimes I feel that way.

I got my new fork seals in today so I started the fork rebuild. The forks came apart pretty easily (other than that big snap ring clip being tough to remove with a small set of snap ring pliers). Rather than just change the fluid and the seal I thought I'd measure a few things like the manual says to do to ensure things were within spec and looking good. I used some calipers to measure the piston dia. and it came out a little bit above the min. spec at 1.558 (min is 1.551).

I have a dial bore gage but it's to large (minimum is 2") to get inside the bottom case. I've a set of inside mics but they are much too short and I would only be able to measure the case at the top by the seal. I'm guessing that the bottom of the case (lower leg) is probably larger than the top since that's where the wear (if any) takes place.

Does someone have a technique for measuring the bottom of the bore?

Now for my "I'm really not a moron" question. After I used my calipers to measure the piston I remembered I had a metric mic stashed away that had never been used (in a previous life it was SAE only).

Can someone take a look at the following pictures and tell me what the mic is reading? The scale on the outside of the mic says it's range is 25-50mm. The 1.551 min dia. measurement for the piston works out to 39.4mm. In my mind that mic is reading about 26.77 mm. Am I missing something here? And, in case you're wondering, those are not my hands. :)

Disassembled left fork. I didn't see any reason to remove the circlips. Is there a reason I should? I've already run the parts through the solvent tank and used stripper on the fork lower. I sure wish people wouldn't take sandpaper to the fork legs. It really tears them up and makes restoration that much more difficult.

Here is the measurement of the piston using calipers.

Here is the same piston being measured by the metric mic.

And last but not least, the manual calls for about 225cc of 10-30 motor oil. Does anyone have any experience using something else? Additionally, I've always found it difficult to accurately measure the amount of fork oil to fill a beaker and, as such, I have a cool little tool that we use on the race bikes to suck out the oil to a predetermined 'oil level height" in the tube. Is there a call-out for measuring the fork oil in this manner?

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I don't mean to intrude, but have you thought about going digital with your measuring tools? I did, and I'll never look back. No brains required :lol:

GB :mrgreen:
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