So I recently got into rebuilding dirt bikes. It’s always been something I wanted to do since I was little and I finally bought my own house with a 1 1/2 car garage so I spent the past multiple months renovating one side into my dream shop/garage. Got me a 1996 RM125 that didn’t run, and stripped it down, figured out the connecting rod bottom bearing where it connects to the crank, bearing shattered and grenaded in the engine. Made a dang mess of the piston and head which I can replace without much of an issue. I found a place to rebuild the crankshaft but I assumed I would need the case repaired as well. I have had two places now tell me that I should be fine to just leave the gouges in the crankshaft area of the case. The gouges are not protruding out where it would catch the crank as it rotates but I assumed it would cause lubrication issues but now I’m thinking I am completely wrong. The gouges are decent but they haven’t created cracks or ruined the mating surfaces which I was told means you can just leave it, rebuild the crankshaft and slap it back together. Just looking for more opinions of leave it or replace/fix it. Thanks. Picture of the piston attached for fun.
Crankcase Advice
- Thread starter AvgDadsGarage
- Start date
-
- Tags
- mechanic
If two experienced engine shops have looked at the cases and both came to the same conclusion, I'd be inclined to trust their assessment. Minor gouges in the crankcase don't necessarily affect lubrication, especially if they're outside the bearing seats and don't interfere with the crank's rotation or the sealing surfaces. The bigger concern would be hidden cracks or damage that could affect alignment.
Since you've already got the engine apart, I'd clean the cases thoroughly, inspect them carefully under good lighting, and make sure no metal fragments are left behind. If the bearing bores are still within spec and the mating surfaces are flat, I'd probably reuse the cases rather than replace them. I'd put the money into a quality crank rebuild and new bearings and seals instead. That said, if the gouges are deep enough to make you question the integrity of the case, it's worth getting a third opinion before you button everything up.
Since you've already got the engine apart, I'd clean the cases thoroughly, inspect them carefully under good lighting, and make sure no metal fragments are left behind. If the bearing bores are still within spec and the mating surfaces are flat, I'd probably reuse the cases rather than replace them. I'd put the money into a quality crank rebuild and new bearings and seals instead. That said, if the gouges are deep enough to make you question the integrity of the case, it's worth getting a third opinion before you button everything up.