DRZ400 Swingarm Chain Rubbing Repair

On a recent full rebuild of both the engine and rolling frame of a DRZ400, I discovered significant wear on the swingarm when it was removed. The location of the wear is on the underside of the swingarm which is hidden from view on maintenance checks and the reason why this wasn't spotted any earlier.

I later discovered that the DRZ400 is prone to the swingarm chain guide wearing out and the chain starting to rub directly against the swingarm and causing wear. This swingarm had done approximately 60,000 km so this high mileage explains the wear. 

Needless to say, checking both the top and underside of the swingarm chain guide is included in my regular maintenance check-overs now.

It’s worth pointing out that the wear in this case was more than superficial. It had actually worn right through the swingarm and breached the bearing and seal cavity of the swingarm. It was in absolute need of repair. Below are some pictures of the DRZ400 swingarm wear followed by the repair before the swingarm was reinstalled back on the bike.

While this swingarm wear is on a DRZ400, this can happen on many different makes and models if the chain guide wears out and is not replaced in time. It is certainly worth checking the top and underside of your chain guide when you next do your bike check over.

Also worth noting is that this is more common on some makes and models than others, especially in cases where the front sprocket is changed to a smaller than stock sprocket. There are many reports of the WR250R having really bad wear when changing to a smaller front sprocket. In these cases, to get the gearing change you want, it can be better to change the rear for a larger sprocket than changing the front to a smaller sprocket.