When it’s time to rebuild your Honda engine, knowing how to read Honda bearings is one of the most important steps. Because the tolerances are color coded from Honda, this makes things a tad easier for you come assembly time, but that’s only if you know how to read Honda Bearings.
Main and rod bearings are a huge part of the engine’s reliability and ability to generate horsepower. Whenever you assemble your Honda engine, you will need to replace the main bearings. The main bearings are responsible for protecting your crankshaft, and all B series, D series and K series Honda engines feature an upper and lower main bearing.
You can tell the upper Honda bearings by the groove machined in it for an oil passage, and a grand total of 10 main bearings in your engine. To properly assemble and torque your main caps properly, you will need to know how to read Honda bearings.
Main Bearing thickness by color
Blue 2.013-2.010 mm 0.0793”- 0.0791”
Black 2.010-2.007 mm 0.0791”- 0.0790”
Brown 2.007-2.004 mm 0.0790”- 0.0789”
Green 2.004-2.001 mm 0.0789”- 0.0788”
Yellow 2.001-1.998 mm 0.0788”- 0.0787”
Pink 1.998-1.995 mm 0.0787”- 0.0785”
Red 1.995-1.992 mm 0.0785”- 0.0783”
When assembling your main bearings and crankshaft in your Honda engine, you can mix and match the bearing halves to create the bearing tolerance desired. Do not jump more than one range in color however, for example ; using a top half brown Honda bearing means that you should mix and match from a Green or Black bearing to complete the bottom half.
Thicknesses and bearing colors are listed from thickest to thinnest, always use plastigauge to properly size and set the tolerances in your engine. If you are using an ACL or King version of the OEM Honda bearing, you can use this simple equation to figure out and calculate bearing clearance.
Bearing Clearance = ID – OD – (2xBT)
To properly calculate your aftermarket bearing clearance, you must measure the inside diameter of your bearing tunnel or housing bore, and subtract that from the outside diameter of the crank journal, finally double the bearing thickness to achieve the clearance value.
Honda Rod Bearings can be slightly more difficult to measure and set, and don’t forget if you are upgrading to aftermarket rods, you must start over to achieve true tolerance. Always use plastigauge and always check your work twice, this will go a long way in helping you learn how to read Honda bearings.
Rod bearing thickness by color
Blue 1.510-1.507 mm 0.0594”- 0.0593”
Black 1.507-1.504 mm 0.0593”- 0.0592”
Brown 1.504-1.501 mm 0.0592”- 0.0591”
Green 1.501-1.498 mm 0.0591”- 0.0590”
Yellow 1.498-1.495 mm 0.0590”- 0.0589”
Pink 1.495-1.492 mm 0.0589”- 0.0587”
Red 1.492-1.489 mm 0.0587”- 0.0586”
Rod bearings are usually required when you hear knocking or the onset of rod knock. When your rod bearings fail, your connecting rods do not receive the proper lubrication and could seize or shatter under load.
Often times, taking apart your engine will reveal burned rod ends or dark rods, and this discoloration is a result of excessive heat. Spun rod bearings will lead to lack of lubrication, which lead to the rods and parts heating up. Rod bearings spin when the oil film between the crank journal and bearing wears down and the bearing no longer can do it’s job of protecting the crank and rods.
While knowing how to read Honda bearings isn’t an exact science without high quality machinist tools, you can do the job with micrometers, or snap tools that allow you to dial in the measurements required. You now know how to read Honda bearings and how to set the tolerances in your Honda VTEC engine.
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