Boss Bearing 79-5007 43mm Sealed Chain Roller
Updated June 26, 2026
This 43mm sealed chain roller from Boss Bearing (part 79-5007) is a direct replacement for the upper or lower chain guide roller on many off-road motorcycles and ATVs. It uses sealed precision bearings to reduce friction and extend service life compared to unsealed rollers.
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What It Is & How It Works
A chain roller is a small wheel mounted on the swingarm that guides the drive chain and prevents it from slapping against the frame or swingarm. This 43mm roller features sealed precision bearings that keep dirt and moisture out, reducing wear and maintaining smooth rotation. The sealed design is especially beneficial in off-road conditions where mud, sand, and water are common.
Vehicle Fitment
This roller is listed for both upper and lower positions on a wide range of Yamaha and Honda models. Yamaha fitments include YZ250 (1987-2012), YZ125 (1987-2012), WR250 (1991-1997), WR400F (1998), YFZ350 Banshee (1987-2006), and YFM660R Raptor (2001-2003). Honda applications include CR250R (1982-2004), CR125R (1999-2004), CR480R (1982-1983), CRF250R (2004-2009), CRF250X (2004-2005), and CRF450R (2002-2004). Always verify your specific model year and roller position before installation.
Common Failure Symptoms & Diagnosis
A worn chain roller often produces a rattling or slapping noise from the rear of the bike, especially under acceleration or over bumps. The roller may feel rough when spun by hand, or you may see flat spots, cracks, or excessive play in the bearing. If the chain is not properly guided, it can derail or damage the swingarm. Inspect the roller periodically and replace it if the bearing feels gritty or the outer surface is worn unevenly.
Installation Notes
Replacement is straightforward: remove the bolt or pin securing the old roller, slide it off, and install the new roller with the included hardware (if provided). Ensure the roller spins freely after tightening. Use thread locker on the mounting bolt if recommended by the vehicle manufacturer. This roller can be used in either the upper or lower position as long as the mounting diameter and offset match your bike's specifications.
