Turning brake rotor.

buzzstpoint

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Did some reading and there have been many discussions saying you can't turn our rotors for the xs400.

Well I'm here to say you can. How do I know? I turned them myself.

Here's a small photo tutorial.

Get yourself a brake lathe.

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Match up your cone,
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Then match your cup.
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Mount the rotor to the lathe, making sure it's square and doesn't wobble,
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Spin IT!!
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Then the finished product.
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I ran out of time so I didn't measure the thickness of the rotor after I was done turning. Had 2 sets of car rotors to turn right after. I'll post the results tomorrow when I get back to work. I also have to order up my bearings for the front. (302S ((National bearings)).
 
Interested to hear what the final result is. In particular the runout. Everything I've read said that solid motorcycle rotors have to be ground to prevent warping.
 
Interested to hear what the final result is. In particular the runout. Everything I've read said that solid motorcycle rotors have to be ground to prevent warping.

Is that for old ones or modern ones? The modern ones are very thin and often multi-piece, but the old ones are super thick and a single piece. I don't know if that has anything to do with it.
 
This is more then likely the older style. It is heavy and just seems to have a lot of metal on it. One piece as well.

IF anyone does turn one on a brake lathe. A few tips. It's not like turning a brake rotor from a car or truck. "Pull the lever and let it go". Here's a couple of videos I made while turning the rotor. The metal is stringy, and balls up. if you let it go it can get mucked up in the bit.
Also about 3/4 way through, the rotor will start vibrating and chattering. You will need to use the clip on silencer.
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But here's some videos for anyone if you are interested.

Clamp up and spin the rotor to make sure it's seated correctly and warpage.

Next, the 1st pass , a small cut to remove the high spots

Then a deeper cut, Couldn't film this on as I had to hold the anti chatter "silencer" and remove the balled up metal from the bit.
 
Is that for old ones or modern ones? The modern ones are very thin and often multi-piece, but the old ones are super thick and a single piece. I don't know if that has anything to do with it.

Depending on who one chooses to believe, it is the stainless steel alloy, the localized heat buildup from cutting, the thickness of the rotor (or lack of it). Automotive brake lathes are designed for cast iron rotors that are many times the thickness of the thickest motorcycle brake rotor. Drilled or slotted rotors are even worse to cut on a lathe. Multi-piece rotors can't be cut on a lathe as the rotor will chatter and deflect.

Grinding rotors can be done by shops who have the proper equipment. But the expense of shipping in addition to their charges often makes replacement cost effective.
 
For most of us it will be cheaper to replace the rotors than invest in a brake turning lathe.
On some rotors, the 7 mm thick one piece rotors as used on many Yamaha's from the same time frame, I could see turning or grinding down to match the thinner 5 mm rotors.
I use two 5 mm thick slotted rotors on my 75 XS650 that the seller claimed came from an XS1100, I don't think they did. I have a slotted set of 7 mm rotors on my 81 XS650. Those I'm pretty sure came from an XS1100.
The standard XS110's, 850,s and 750's used the same 11.7 inch rotors as the XS650. The Special versions of these bikes used 10.5 inch rotors. There are many different rotors off other bikes that will bolt to the XS650 and XS400 hubs. The offset and size varies but if you go to a Brembo our other sport bike calipers the adapter plate needed will compensate for these differences.
Leo
 
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