Yes they certainly will break. It happened to me with my 82 diesel Westy.
The Stooge that installed my engine (was sold as "new" but was a polished junk
yard relic-won't go there now) neglected to replace the timing belt cover.
When  I asked him why he said that I really didn't want that on there because  a
rock could get caught inside of it and break the belt?! Well just the
opposite  happened. A rock spun up and broke the belt, bent valves and resulted in
replacing the entire cylinder head to the tune of $1600.00. Granted this was
not  death by natural causes but more of a freak accident that left me madder
than hell anyway. I was young dumb and ignorant and learned an expensive
lesson.  I work in the service dept. of a Honda dealership and we replace most
timing  belts at 7 yrs. or 105, 000 miles per Honda's recommendation. We usually
don't  see many break unless they get to about 175,000 miles or more. Honda
realized  this and saw that many people were dismissing this as Honda's attempt to
 generate more business in the service dept. before it was really needed.
What I  have seen now is that the timing belts on the new Honda v6 engines are
thinner  and narrower than the ones that were used on the early 80's Civics!
Maybe  they are made of a stronger rubber compound or maybe they will truly fail
around  the end of their predicted life span. Timing belts will fail, not
often but it  does happen and when it does an interference engine will require
big bucks for  valve replacement and head work. It can be an expensive gamble.

David Clarkson
90 Westy (240k)

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