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what is this on my bearing?
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ah, dont worry about this. just figured it out
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That means that there is some wear on the rotor bearings, you might be able to re-use them. But, since you are rebuilding the engine might as well replace them.
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every s/h bearing has this mark through the babbit metal across the puzzle lock area.. totally normal and does not represent that the bearing is ruined .. new bearings can be problematic and unless its fully necessary dont change the bearings just for the sake of changing them
if you do . run in period is much extended and needs to be followed |
How much longer would you say is required for the break-in/run-in period when you've got all new bearings, as opposed to used but good condition ones?
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i originally made the thread as i *thought* it looked like the bearing surface material (babbit?) had been worn through. then i saw the same thing in a rebuild video and realised it was normal. every other pic i'd seen must have been taken from a different angle, not showing that patch!
i'll get in there with a bore gauge and see what's going on |
http://www.mazdaspeeddevelopment.com...g/techtips.pdf
TT23 pretty sure there used to be an RB chart hanging around with an even more extended run in for new bearings and advise to leave old but spec bearings if they are sound // if you read those tips above you will glean important tips about bearing tolerances .. basically higher rpm = looser . and so quite often older bearings are closer to ideal than new ones if using new bearings a similar trick is to dress the crank slightly.. however i advise all rebuilds, new bearings or not can benefit from a little effort and a careful hand linish of the crank journals with paper and kero and shoestring |
Rotary Tech Tips: Engine Rotors
All rotor bearings, stock or Mazda Factory Race (MFR), are made from a flat piece of steel which is stamped, rolled, and hooked together at the joint with a "puzzle lock" design. This bearing is then coated with copper and plated with about .0015" of Babbitt bearing material. The inside surface of the puzzle lock joint area is ground off to eliminate high spots, usually resulting in a portion of the copper coating being exposed. This appears, to the untrained eye, to be a worn spot on the bearing, but is in fact normal (See Photo). Rotor bearings do cause occasional problems during high RPM operation. It is important to use properly clearanced rotor bearings. In general, do not replace rotor bearings when you are re-using rotors unless they are over the recommended clearance or show some damage from dirt, heat, or lack of oil. Our experience has shown that used bearings in good condition are safer than new, untried bearings. For high performance street and racing use, the best rotor bearings we offer are Mazda Factory Race (MFR) rotor bearings with a deep oil groove and additional clearance (approximately .0005" extra). While stock bearings can be grooved deeper and polished to obtain additional clearance, the MFR bearings are still the better choice. The MFR groove is approximately .070" deep to provide an improved reservoir of oil around the bearing. Up to 8,500 RPM, .003" +/- .0005" eccentric shaft-to-rotor bearing clearance is acceptable. Beyond 8,500 RPM, clearance should be .004"+/- .00025". Clearance can be adjusted by polishing the inside of the rotor bearings with 400 grit or 600 grit wet-or-dry sandpaper strips which are spun with a high speed motor such as an air powered die grinder. |
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