The crankshaft on my 250LC was stored in plastic bags drenched in oil many years ago. Upon removal it seemed to be in good condition and the bearings seemed ok. How do I go about degreasing it and removing any contaminants that may be on it. Is it just a case of placing it in petrol and giving it a good swill around. Thanks.

NO !!! Not petrol, use a degreaser something like GUNK will do or even hot soapy water at a pinch, all you want to do is make sure that the oil ways in the crank are not bunged up, you can use an air line to blow them through and just soak the crud off. Any degreaser will do as long as you remember to wash it off and oil the crank after you have it clean.

I would clean it in diesel and then a degreaser. I would also get the big end changed and the crank balanced. Do it once and do it properly as you will waste time and money if you have to strip down the engine again if the big end is knackered. You can send them away to get them done search tinterweb for PJME.