Originally Posted by 650x
As noted in this thread, there are two schools of thought concerning repacking sealed bearings. Having been an electrician in a sawmill, I have dealt with a lot of motor bearings. From my experience in dealing with large electric motor bearings, over greasing is the leading cause of bearing failure. IMO, when dealing with a high speed application such as a motor, when using sealed bearings, don't add any grease, just install and run them.
Many years ago I felt packing sealed bearings full of grease for use in a motorcycle wheel was a bad idea and didn't do it. However, I was going through bearings (especially on the rear of my first 520) and found the failure was due to moisture and rust. I was having to install new rear bearings on my old 520 almost every time I replaced the rear tire (2 -3 times a year) Decided to try repacking new sealed bearing fairly full with water resistance (boat trailer) grease. Since then, have been going through a lot less wheel bearings. Still pull them out at least once a year and clean them out and regrease them, but don't have to replace them very often.
IMO, packing sealed bearings for a motor application is still a bad idea. However, I now believe that motorcycle wheel bearings are a different matter all together. The speed is much slower and rarely constant like a large industrial motor. Don't believe they get hot enough from the speed they see for the extra grease to be a problem. Do believe the boat trailer grease will help keep the moisture and other dirt out and usable grease in where it needs to be.
It is your bike, so do what you feel is best. For me and my bikes, I now always pull the seals and clean out the stock grease and fill them with water proof grease. Works well for me.
You know I said that too and people told me I was crazy, oh well. It goes for front wheel bearings as well or any bearings on our 640's. I use Red wheel bearing grease.It will take the high temps of disc braking and hold up but remain fluid at low temps, available at Ace hardware. Completely waterproof. Great for the pivot, swing arm and steering head too.