Thanks a lot Dazzler_be,

This explanation makes a lot of sense to me, I was just thinking about the crankshaft but didn't think about the dirt on the ground that could scratch the engine. I've fixed some smaller engines so I think I won't have problems with this one, the only problem is that my local hobby shop is out of fixing parts for my engine so I'll have to buy at tower or something like that (which is not a problem except because I live in Costa Rica and the parts will get here in 2 weeks or so!)

Anyway, I'll take your advice and will check everything for wear... seems like an "overhaul" is waiting!

Thanks again for your help! I'll keep U posted