What would cause backfires????????

[jonjonwells]

As the question states, I have a ski that is backfiring. When it does it, there is a loud pop out the exhaust and the rubber connecting pipe between the stinger and waterbox flattens out. Any ideas.

[z00m]

Timing is out,
loss of power for a second,
cut off switch earthing out for a second,
over fueling
underfueling,
faulty stator
faulty cdi

unfortunatly there are quite a few causes

mick

[jonjonwells]

umkay, well that sucks. I was hoping for something easier. Oh well, off to work then.

[ph2ocraft]

jonjon, use a jumper pack and see what happens.

[ph2ocraft]

If it fires off with no more back firing it's the battery.
The 2nd most common reason for a backfire is a bad stator, test it as outlined in the tech section.

[00pro785]

My backfire was from a out of index crank.

[xlint89]

I backfire when I have beans. Backfire out the waterbox is usually rich, is your choke stuck closed by chance?

[jonjonwells]

Nope on the choke. This ski sat with about 8 inches of water in the hull for 3 days. The owner fired it up and somehow it ran like crap (duh). Pulled the plugs, found one of them was smashed, like someone took a hammer to the tip. Also found about an inch of water in the CDI box. Did a full rebuild on the carbs just to make sure there wasn't any mud/water in there (there was).

Possibilities:

Crank out of index
CDI fried
Stator Fried
Coils weak

[SeaLion]

Broken reeds can also cause a backfire or are a result of backfires. Don't forget to check the reeds.

[xlint89]

Make sure the carb orifices are completely clean. A little dirt particle can clog it and cause the backfire. Also make sure the elec box is not rusted on the board, including the bottom side.