XS650 engine rattle - help needed please

[Warr]

Motu suggested it would be rare for a catastrophic like this to occur. Do you have any ideas why??
Dirty oil, too long between oil changes ...

Not likely cam bearings on an XS650,they have substantial double ball bearings each end.Pull the tensioner out and have a good look at it,they have a sprocket which runs un the chain,this could be worn or out of aligment,also check the chain guides......which you can't unless you pull it apart again.Check the advance retard mechanism for play,and also the shaft - this too runs in neelde rollers each end,they get dry and sticky.Rest assured that no noise in an XS650 is cause for concern,they are way over engineered and can be destroyed only by immersion in the crater of Mt Doom.

[surfer]

Motu suggested it would be rare for a catastrophic like this to occur. Do you have any ideas why??
Dirty oil, too long between oil changes ...

Yes, I have an idea but am not certain yet. Basically I think it has something to do with the groove that appears two thirds of the way down the barrel. The groove is at the front of the piston and below the piston rings at their lowest point.

I have no idea how the groove got there, it might have been caused by the piston but it is a funny shape for this as it doesn't match the piston shape. Or it might be a mistake that someone has made at sometime in the past. Failing this my money is on aliens.

It may be that the piston skirt is catching in this groove and this is throwing the piston and connecting rods forward causing damage and wear to the big ends. However, this is theory only. I am off to seek some advice from an engineering shop with the offending barrel.

I will put up a post and let you know.

[Motu]

They have an all roller and ball bottom end - they don't need oil pressure just flow and not much filtering,the XS650 has a couple of mesh filters.Age,really,really,really old oil or none would do it.Friend of mine ran an old XS650 on waste engine oil he poured into a drum....it did finally die,but took some time doing it.

[surfer]

Motu suggested it would be rare for a catastrophic like this to occur. Do you have any ideas why??
Dirty oil, too long between oil changes ...

Yep, dirty engine oil was the culprit. Previous owner couldn't have liked changing oil.

They have an all roller and ball bottom end - they don't need oil pressure just flow and not much filtering,the XS650 has a couple of mesh filters.Age,really,really,really old oil or none would do it.Friend of mine ran an old XS650 on waste engine oil he poured into a drum....it did finally die,but took some time doing it.

Motu yes, you are right. Cheers.

I took the barrel into the local place near me, Engine Specialties. They reckon the groove is a machinists error in setting up for a rebore when the barrel was rebored. They are measuring the pistons and barrels for me though.

The piston and barrel seem to have suffered a lot of wear and has signs of running on dirty oil as there are marks running down the sides of the pistons to indicate this as well. This would also account for the damage to the crankshaft.

Many thanks everyone for your comments, suggestions and help. Much appreciated.

Onward with the top end rebuild now.