Q: What are bearings made of?
A: Standard steel bearings are made from a high carbon chrome steel known as AISI 52100. It has around 1% carbon and a little bit more chrome. Stainless steel bearings are made from a group of high chrome steels called 440 Stainless. These steels have around 1% carbon but differ from bearing steel in that they have between 12% to 18% chrome.
Q: A magnet sticks to my stainless steel bearings! What gives?
A: 440 series stainless steels are what is known as Martensitic steel which is magnetic. Stainless steels used in your sinks and other appliances are usually a 300 series which is non-magnetic but much softer.
Q: My original front bearing only has one shield. The one you sent has them on both sides. Do I need to remove the inner one?
A: The short answer is no. The reason for this is that there is a small gap between the inner race and the shield. This gap is a lot bigger than the gap between the crankshaft and crankcase. Any oil that is able to get through the crankcase gap will easily get into the bearing.
Q: My engine leaks a lot from the front. Is this from a bad bearing?
A: Unless the engine was designed to use a sealed bearing, leaking from the front has nothing to do with the bearing. Leaking from the front is due to excessive clearance between the crankcase and crankshaft. This can be caused by uncontrolled manufacturing tolerances, or wear from dust and dirt. Usually, using a sealed bearing can stop the excessive leaking.
Q: My engine won’t shut off when I close the throttle. I was told that a defective bearing was letting air in. Is this true?
A: See above. There are a lot of other sources for the air leak, such as a loose backplate, loose throttle barrel, missing o-ring at the carb base, etc.
Q: How come your bearings are so inexpensive?
A: I don’t have the high overhead or complex distribution channels to maintain (or pay for) that many other places have. I get my bearings from some of the same manufacturers as many of my competitors. I have been flying model aircraft for 40 years and I just don’t feel like taking that much advantage of fellow modelers.
Please let me know if you have any other questions
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