by Malcolm » Sun Aug 22, 2004 11:00 pm
i think the fact that it's only doing it when cold points to them just being quite worn, probably from not having regular oil changes, or possibly just from high km's. Big ends are pretty simple and cheap to change, just need to drop the sump off, remove oil pickup, remove conrod bearing caps and replace bearings, then put it back together and reseal the sump.
When it is an issue, however, tends to be when it's been run dry of oil when at full operating temp + high revs. This combination usually creates a somewhat more damaging result, with the bearings' coating disintegrating and flaking apart, usually scoring the crank and putting shavings through the engine. At this point you need to remove the crank and get it reground and get oversized bearings. This wont protect you if there are bearing shavings in the oil galleries, but it's a relatively cheap fix and should be reliable if done correctly.