Loud Bang After Starting Up?

Upon leaving work this evening, I started the bike up and as soon as it fired up an enormous loud bang bellowed from the exhaust area.

Can anyone explain what this would have been? as it's the 2nd time it has happened to me.

Bike has been left standing outside office for 12 hrs.

Prankster at the office?

[Spanner Man]

Good morning.

It sounds like an excess of un-burnt fuel in the exhaust igniting. Did the engine crank for a few seconds before starting?


Cheers.

I get this now and again but from the front I was told the most probable cause was as spanner man said excess unburnt fuel, maybe due to the battery being a bit low on power.

Loud Bang After Starting Up?

cool!

fwighten old ladies and stuff

Originally Posted by Spanner Man

Good morning.

It sounds like an excess of un-burnt fuel in the exhaust igniting. Did the engine crank for a few seconds before starting?


Cheers.

Yes, that exactly what happens...thanks Spanner Man.

at first I thought it may have been those pesky kids who live near the office, had put something down the exhaust.

If thats it though, I'll breath a sigh of relief.

[Sid Squid]

Discount the temperature element, the principle remains:

Originally Posted by Sid Squid

If you fire up your bike from cold in marginal conditions, it's not unusual to get either a partial, or sometimes a complete misfire, the resulting unburnt fuel rich gas gets shoved into the pipe on the exhaust stroke, next charge goes into the cylinder, fires, and then extremely hot gas gets let into the pipe where aforesaid eminently burnable gas lies waiting to p*ss your neighbours off, voila , big bang in the pipe, enjoy.

Possible causes:

Plugs need a clean/change.
Battery voltage low: Poor quality and duration sparks.
Old or contaminated fuel.
Incorrect choke setting.
Itr's bloody cold out.

[fastdruid]

Originally Posted by Sid Squid

Discount the temperature element, the principle remains:

You forgot one from that list:

It's a Honda or old Suzuki and you've been cranking it with the kill switch set to OFF.

Druid

Originally Posted by Sid Squid

Discount the temperature element, the principle remains:

Thanks Ian for the extended explaination...the 1st 3 I can pretty much rule out, so will get the choke settings checked, as it wasn't that cold around 9pm last night.

Wouldnt worry about it, I got that a few times on my curvy. My bike is parked in an underground car park to, the first time mine did it, it scared the sh*t out of me!!!!

Its done it a few times and doesnt do it anymore.