the 2RS on those bearings means 2 rubber seals.....they removed them.....and I bet they are not a C3 clearance fit - Which all crank bearings must be. Like Jason stated.....I'd source out some KOYO 63/28C3 bearings and do it right.
Honda Part# 91008-KAE-000 or 91008-KAE-731 <- these are the 8 ball version (stronger bearing)
All two stroke crankshaft main bearings are not C3 clearance. C3 clearance is the most common bearing used in electric motors but not in two stroke engines. When the engine manufactures have Koyo or any other bearing manufacture make a large production run of bearings, the engine manufacturer that will be using the bearings will usually request the clearance not be printed on the bearing. Some engine manufacturers use different interference fits on the OD and ID of the bearing. The engineers seldom request clearances tighter than C3 but often request clearances looser than C4 or C5.
There are a lot of general specifications for bearings that are intended to be sold over the counter for small projects or to engineers that are building and testing proto types. The markings on these bearings are accurate and are what they are said to be. If there are clearance, finish, and tolerance, markings on the bearings that were installed when the engines were produced, they are usually not accurate. The inner and outer races for all ball bearing of the same OD and ID, are the same. The internal bearing clearance is determined by the size of the balls.
You are probably asking why the markings for clearance on the OEM bearings in a new engine or the bearing sold through the engine manufacturer dealer network, may not be accurate? Bearing manufacturers often produce large runs of C3 bearings since this is the most common clearance, so they mark the outer race of the bearing C3. Then one of the two stroke engine manufacturers calls a bearing manufacturers and needs a rush order of 10,000 bearings that need a C4.5 clearance. The bearing manufacturer tells the engine manufacturer that we have 100,000 inner and outer races already made but they have the C3 label and it will be two months until we can make your bearings without clearance marking. The engine manufacturer does not care what is printed on the bearing as long as it has the balls installed that gives the bearing the C4.5 clearance, like testing has indicated is absolutely necessary. The engine manufacturer through it's dealer network, is supplying the customer with a bearing that has all of the dimensions that was supplied when the engine was new, even though the clearance marked on the OEM bearing was wrong.
If you buy your parts from Honda or any other OEM part, it will have the correct dimensions that engineers found to be optimal through extensive testing. Guys that are attempting to save money by taking their old bearing to a local bearing supplier or ordering bearings online using the numbers that were on their OEM bearing will often experience problems because the new cheaper bearing does not have the correct dimensions for the application.
The moral of the story: Buy OEM parts unless you have the experience and tools to accurately measure and determine what clearance a new OEM Honda bearing had. Most often it was not a standard mass produced C3,C4 or C5 bearing. If the OEM bearing had a C4.5 clearance, it is going to cost you a lot more than having custom bearings made to Honda's specifications than paying retail cost at a Honda dealer.
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