jammerrs

just saw a motorbike go past and as he eased off the power it backfired, made me wonder what causes it?

sad i know

24vcossiemat

excess fueling i think mate

jammerrs

ow right then reigniting

cheers mate

24vcossiemat

yeah thats right, normally in the exhaust side. extremely hot exhaust equals bang,.. done, as gordon ramsey would say

foreigneRS

on a motorbike it might be that the rider switched off the ignition and because the engine is still sucking fuel in through the carburettor(s), when you then switch the ignition back on you get the unburnt fuel igniting - sometimes several meters behind you if you do it right

what kind of motorbike and where was this?

Glenn_

iTrader: (1)

i heard a motorbike the other night and that was popping and banging. He was reving it a bit though.

studabear

back fire, after a real hot curry?

jammerrs

erm, crosser/supermoto thing, was going up a slight hill then backed off as he caught the car infront up

burnzy

isn't it also exhaust pressure on some engines that'll cause the popping , i always thought it was fuel if there was flames but just popping was due to the change in pressure in the exhaust.

24vcossiemat

dunno, i just thought it was excess unburned fuel igniting in the exhuast system

foreigneRS

that's more just popping on the overrun due to excess fuel rather than backfiring

steves24V's

iTrader: (7)

Ha ha i used to do that in my nova ok should of kept quite about the nova bit.

24vcossiemat

that looks a rather smart sierra mate, liking the 24v bit

RichieST

iTrader: (2)

Yup, its unburnt fuel igniting in the hot exhaust.

Some turbocharged cars do it too (my ST does it, along with cossies etc) when its really hot, I think the theory behind it is the ecu squirts in fuel on the over run to help cool the cylinders, can cause a bit of black smoke too. I stand to be corrected on that one though!