Needle Bearing Oil Holes - Is It Necessary?
Have you ever pulled apart a gearbox on a vintage Triumph, or classic BSA motorcycle and noticed that some of the needle bearings have holes on the outside? If you have wondered that, then you need to read this blog post. I will get further into detail specifically on needle roller bearings and the "oil holes" for British motorcycles. But first there are a couple questions you need to ask yourself. What is an "oil hole" needle bearing? Why do some needle bearings have oil holes on the outside? Does it matter if I install a needle bearing with or without an oil hole?
BSA "open end" needle bearing. Notice the "oil hole"?
There is usually a reason why a manufacture will choose to use a needle bearing with or without an oil hole. It all depends on oil supply. If the bearing is in a location in which not enough oil can lube the rollers, then an oil hole would be essential. Usually there will be a channel machined into the housing in which oil can be directly funneled through the oil hole. Above is the 42-3075 BSA needle roller bearing by Koyo which has an oil hole on the outside of the housing.
Needle bearing box by Koyo bearing Corporation. "OH" = "oil hole"
The term "oil hole" comes from the manufacturers description and unique function of the bearing. Oil hole is also known in short as "OH". When you purchase a needle bearing, usually on the box the manufacture will state that the needle bearing has an oil hole by putting the "OH" prefix on the box. Above you will see the "OH" prefix that Koyo needle bearings put on there box. If your manufactures box does not have the "OH" prefix, chances are the needle bearing does not have an oil hole.
BSA unit twin gear box machined oil feed tunnel
The BSA A65 gearbox has a machined channel in which it acts as a funnel for the needle bearing that has an oil hole. Today, many manufactures are not making needle bearings with the oil holes that are specific to our applications. When I refer to "our applications", I am referring to us vintage Triumph, and BSA motorcycle owners. The BSA twin closed end needle bearing and open end needle bearing for example both should have an oil hole, even the BSA parts book states the needle bearing type followed along with "OH". I am always searching for the "correct" bearings for our applications and as of now I have only found the open end bearing for the BSA that has an oil hole. For Triumph twins, I have in fact pulled out needle bearings that did have an oil hole, but the oil hole is irreverent as there is no machined channel for the oil in the gearbox. The following will answer the next question, "does it matter if I install a needle bearing with or without an oil hole?"
BSA parts books outlining the bearing specification.
If the manufacture of your motorcycle calls for an oil hole needle bearing, by all means install what they recommend. However, as stated earlier in this blog, it is often difficult and rare to find needle bearings for vintage Triumph motorcycles, and BSA motorcycles that have the correct oil hole. Most needle bearings on the market today for our singles, twins, and triples do not have the oil hole. I have personally found that if you installed a needle bearing without an oil hole in a vintage British motorcycle, chances are it will be fine. There is usually enough oil in the gearbox "sloshing around" to lube the rollers. Now I cannot state this for every application, but I can tell you that based on most Triumph and BSA models you should not have any problems... In fact, most vintage Brit bikes on the road now probably do not have the oil hole needle bearings installed.
Everyone knows what this means....