Rust?

[hetasfireplacefitter]

Hi all. Engine has been running fine apart from a slippy kick starter and bad carb settings. Bike is all apart for new bearings. Inspecting the crank I find this. I lightly polished off what I could quickly and took the picture. More can be polished but it must of been running like this. Any views as to why and what next please.




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[knackeredMk1]

Bike got flooded? But most likely some condensation in the crank. Also part burned fuel and oil can be acidic and collects on the bottom of the crank if the bike is left unused for long periods. Not a problem unless rust is in the bearings or on the bearing surfaces. You will look hard to find engines of the age of the CRM without some of this.

[hetasfireplacefitter]

Thanks knackered. It did sit for a while before I got it. The bearings are as clean as a whistle. Seems it's had a rebuild of the bottom end and then just never serviced and ran into the hills. Shame they didn't change any other bearings. Swing arm was fun[FEARFUL FACE]

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[fallenmikethebike]

Intensive jet washing, followed by running the engine for a short duration can add to the problem.
The filter gets wet, then the moisture is drawn in the crank assembly, which if not hot will not allow the moisture to be evaporated away.
Mike