Star hub

[Robert Luland]

I always thought the most thankless and filthy job on a Harley was taking a pogo stick apart. I was wrong. Yesterday I took eight star hubs apart. What a degusting mess. One of the hubs has a very light pitting to the touch on the large bearing race. Can this be lightly honed? How would you do it or is there someone that offers this service? It would be a shame to have to discard it. Thanks lads, bob L

[Chris Haynes]

Discard it ovah heah!

[Rooster]

Bob, I reckon I'm partly a nut case, because I thoroughly enjoy going through star hubs! I think they're fun!
Some 'light' pitting won't hurt, it may cause some noise, but you'd be hard pressed to hear it. It will do no harm, other than slightly accellerated wear. I know of no way to hone them, but I would be interested to hear if anyone does it.
There are still plenty of good hubs around if you need to replace it.

[Chris Haynes]

You can use the same hone you use on Sportster and 45" rods.

[koanes]

I use my motor bearing race lapping tool on with a homemade pilot on the drum side. It is often neccesary to remove some high spots on the spot welds that hold the spoke flange to prevent damaging the lap. The drum side is a little tougher, the lap head needs to be modified by removing any tapered lead so the lap makes full contact at the back of the race. If the races are not out of round and require only a light hone to remove pitting, the star side can be hone with a standard mandrel on a Sunnen hone. The drum side requires a special blind hole mandrel not often found at your average auto machine shop. If the races are round and true, the pitting will cause no problems. I have run properly maintained moderately pitted races for tens of thousands of miles with no problems.

[T. Cotten]

It should be emphasized that by "pitting", we are speaking of spots eroded by corrosion, as opposed to "spalling", where hardening has actually flaked off.

Under magnification such as a cheap eye loupe, there should be no sharp lines within the pits that appear like crystal structure or cleavage planes.

Otherwise, corrosion pits just hold lube!

....Cotten

[Robert Luland]

Thanks everybody. Tom it's just a couple of slite corrotion marks from the bearings sitting in one place for to long. I agree. I'm gonna run it just the way it is. Bob L

[T. Cotten]

couple of slite corrotion marks from the bearings sitting in one place for to long.

Which brings up an interesting question:

Why does "corrosion" form at the contact of bearings, and not uniformly everywhere, if moisture or rust is the culprit?

I read that it is the same thing that is destroying the Pyramids.

....Cotten

[Paps]

Two possible reasons....One....metal cools down cooler and heats up hotter than the actual air temperature it is in. Look at it like a refrigerator collecting moisture out of the air. The moisture condensates to the metal. Two.....pretroleum floats in water thus the water settles. Water is H2O. The O rusts the unprotected metal surfaces.

[Sargehere]

"Surface tension" of the water causes it to accumulate in cracks, or at the intersection of two pieces of metal, like where the rollers meet the race.

[T. Cotten]

Pa And Sarge!

Both of your scenarios rely on substantial water dissolved in the lube to separate to the bottom, and attack the metal.
(Particularly if it is to have a surface for tension!)

Why then does this take decades to manifest itself, instead of sitting for just a winter? Or even just a few weeks?

With motor mains, shouldn't the right main drain itself if left on a kickstand?
Yet they commonly display the same "corrosion" as left mains found with them.

Nobody is going to bring up any acids formed within the oil?
(It wasn't acid rain attacking the Pyramids that I referred to... Although it probably does!)

It is easy to imagine water from combustion in motor mains, but it is hard to imagine so many star hubs put away with moisture dissolved into heavy grease.
Grease itself was the water seal in VL trannys and the like.

...Cotten
PS: Pa! Your description of the 'refrigeration' effect is a little confusing, however it sounds like what I was tought as the notion of "driving force".
It is why I believe front cylinders run hotter than the rear.
Yet I cannot see how to apply it to a process that must take a generation to manifest itself.
There should be no supply of water beyond that contained within the oil when the machine was parked. (Hopefully, or a real water-line would be produced!)

[MJW]

Last weekend I dumped remaining gas from several outboard motor fuel tanks into a clean bucket. after a while I could see a definite line between the gas floating on top, and about a gallon of water on the bottom. You'll say "that's condensation" but in a sealed tank, how did the water vapor get in? I've heard of old motors that have sat for long periods that were half full of water....Mike

[Paps]

Water is often a vapor such as normal air. It will find its' way in the smallest openings. I tend to think that maybe the carbon content of a bearing may speed up the rusting processes. Back to how the water gets in...Crankcases must breathe so they do possess an opening for such breathing. I assume hot engines act like hot muggy humid weather. As the day cools, so the engines cools also. The humidity collects in weather and rains. The humidity produced by the engine does likewise. Cold weather works bascially the same. Snow and ice form from it on cooler surfaces such as the atmosphere and metal components. I still think the O in water is the main culprit involved though. But carbon content helps speed up that rusting process with O. The two together may be the defining chemical reaction, or acidity.

[bmh]

Someone had posted earlier that the pits just hold grease. That may be true, but they still weaken the bearing by removing surface contact area. Every Time a roller bears weight across a set of pits (and usually only 3 or 4 rollers are bearing the entire load placed on that bearing) the pressure on the race surface is increased dramatically. Very easily beyond the design parameters of the race surface. While the grease in the pits will help keep the race from overheating, it will not prevent the edges of the pits from eroding away farther due to the increased pressure placed on the race in cross section. And those bits of race material turn your grease into a very fine lapping compound with use, putting fresh grease in through the Zerk does not remove the contamination. All the bearing service info I have states the same thing. Races found pitted or scored must be replaced, there is no distinction on what caused the pits or what the grain structure of the metal at the bottom of the pits looks like.

As to the cause , this is my theory. It's usually the right side bearing race that's pitted up. When parked on a jiffy stand, that side is angled up and would gather water when it rained. The water would work it's way in and small amounts would eventually get trapped behind the thrust assembly and emulsify the grease, leading to pitting.

[Magic]

Dirty bikes rule

This is all evident of why I don't wash any of my motorcycles often especially the wheels. The inners rims stay cleaner rust free as well as the bearings axels always have a little extra grease outside to protect the insides. Alot of older M/Cs not ridden enough and washed to much fall prey to these demons. I think I'll go out now and massage some Lexol on the seats. Merlin in Pa.