It is very possible for an engine backfire to cause a fire to start
IF there is fuel for the fire. Your mower could have caught fire
due to a backfire if: (1) It already had a gasoline leak when you
loaned it to the neighbor, or (2) the neighbor could possibly have
caused a gasoline leak, or (3) the neighbor spilled gasoline from
the storage can while the engine was running, or (4) the neighbor
spilled gasoline from the storage can while filling the tank and
then started the mower again before cleaning the spill or waiting
for it to evaporate, or (5) the neighbor tipped the mower sideways
to access the blade area and spilled gasoline from the gas tank.
If a 15 year-old was operating the mower, then (3) or (4) or (5) is
extremely possible and it would also be extremely probable that
the boy wouldn't admit to it. A boy in our neighborhood destroyed
a mower by error (5) - he stopped the mower, tipped it on its
side to clear some damp clippings, started the mower again, and
watched the mower catch fire.
Who pays to replace your mower? Conventional "good old boy"
guidelines say that if it broke while somebody borrows it, then
the borrower repairs it or replaces it.
I'm not that rigid on tools that I loan out. If I feel that the damage
was not the fault of the borrower, then I feel that he has no obligation
to repair or replace. If I know that my mower leaks gasoline and
tends to backfire and I loan it to you, then I'd say that a fire was
bound to happen sometime soon. Likewise, if you borrow my car
and the fuel pump or the starter fails, you aren't at fault since that
part was due to fail. If you borrow my mower and the throttle control
cable breaks, I would refuse to accept payment for that part which
died of old age.
On the other hand: If the damage occurred because the item was
loaned out, then the borrower should offer to make restitution by
either repairing the item, replacing the item with one equal to or
better than the borrowed item, or pay me a fair replacement price.
If you borrow my car and you dent it, or it is dented by somebody
else while you are using it, or you hit a curb and cause a tire
sidewall failure then you pay. If you borrow my mower and pinch
the throttle cable by folding the handle improperly, then I expect
you to take care of the repair. I'd expect you to offer to repair it
that day or deliver it to a repair shop that day.
(Actually, I'd be happy if you went out and purchased the part
immediately and the two of us replaced the cable in my garage
If I were your neighbor, I'd offer to replace the mower, possibly
with a $50 copay on your part since the mower was 3 years old.
If you hesitated even slightly about paying a $50 share of the
cost of replacement, then I would not hesitate to pay the entire
amount. Without evidence to the contrary, I must assume that
my 15 year-old son is at fault. How many 15 year-old boys
take warnings seriously or admit to big mistakes willingly?
FYI - I have offended several friends by refusing to loan them
one of my lawnmowers. In fact, I generally will not loan any tool
with a cutting edge - for both liability reasons and for tool damage
reasons. For some of my moron friends, neighbors and relatives,
I won't even loan them a screwdriver.
I assume that you are trying to determine who pays for a new
mower. You didn't mention anything about your neighbor or his
son offering to buy you a new mower, so you've already got a
problem on your hands.
m Ransley wrote
My neighbor borrowed my 3 yr old Cub Cadet walk behind 6.5hp with
Kawasaki engine. It caught fire while they were cutting the grass and
has been junked , it is gone to the dump. My neighbor said it backfired
then they left it and it burned. The kid cutting it was 15 and I figure
he put gas in it while hot and it splled catching fire. But a different
neighbor heard it backfire . I know a backfire can cause a flame out
the carburator possibly causing a fire. But my question is this possible
for a good mower to catch fire from a backfire , or is the only logical
explanation is he was refilling the mower while hot and caused the fire.
Im just curious and have googled for 'Lawnmower fires" and find nothing
showing a possible defect to cause a fire.