and yet another timing chain question

if a timing chain jumps or breaks at idle, what are the odds of no engine damage? there is an 80 750 in ebay near me and i was just curious,,,tia

Personally, I think the odds of there being no engine damage in either case are pretty low.

Don't bid any more than you are willing to pay if you knew for sure the engine was total junk.

Post edited by: steell, at: 2006/03/12 23:05

Well, Steell is probably correct...odds are in favor of having some serious motor damage. However, if you were ever to break a timing chain, 'at idle' is when you want to do it. As an aside, my wife bought a new 1993 Hyundai Excel. The manual suggests that the timing belt be changed every 30,000 miles. Turns out that those clever Korean engineers weren't kidding as at 30,000 and 60,000 miles (approximately) the belt broke, but 'at idle'. That's right, twice...at neither time did any engine damage result. So, it is possible that there is no damage to the bike in question, but odds are in favor of damage.

I´d say the odds are very very slim. For example in my ELR the chain has no room to move over the sprockets. So if it breaks it will most probably be jammed around the crankshaft or cam sprockets. Also a potentially big damage comes from valves hitting the pistonheads i.e. engine is still on high rpm but cams are not which means the valve can be fully open when piston comes up. Breaking or bending a valve att 8.000rpm is no joke.

The reason why some engines are not damaged by this is that valves have clearance over the piston at all positions. Also there´s no chain but a belt which is usually located outside the block.