Backfiring

[Skyryder]

Anyone got any ideas what's causing this. It does not backfire when engine is cold, Does when changing down and at the lower end of the revs as the back pressure is getting less. 36000k's on the clock. Just gota get this sorted as it's getting worse.

Skyryder

[98tls]

its either your pipes...as in fucked or your mixture is running to rich....if its to rich it will burn off the excess in your exhaust...ie...backfiring

[T.W.R]

If it's genuine backfiring it's too lean air/fuel mixture or incomplete intake valve closure.
If it's after firing it's a manky plug, too rich air/fuel mix, retarded timing, or incomplete exhaust valve closure.

[98tls]

ahhh..this will be interesting......hey fellow old bugger...if its backfiring it must be to rich......

[Ixion]

A dud plug or other electrical "make spark not happen" thing can cause "bac firing" - the mixture not burned on the missed cycle is pumped into t he exhaust pipe and ignited on the next cycle when the cylinder does fire.

If the missed spark is not frequent the misfire may pass unnoticed , masked by the "backfire" .

[scumdog]

An exhaust leak up by the cylinder head can also be a cause.

[Motu]

Too lean....or rich with an exhaust leak,you need to get extra oxy to the unburned fuel.

[sAsLEX]

ahhh..this will be interesting......hey fellow old bugger...if its backfiring it must be to rich......

I was always told lean....

An exhaust leak up by the cylinder head can also be a cause.

Also look at any joins with collars for leaks ie the 4 into 1 bit etc

[mjvduc]

Anyone got any ideas what's causing this. It does not backfire when engine is cold, Does when changing down and at the lower end of the revs as the back pressure is getting less. 36000k's on the clock. Just gota get this sorted as it's getting worse.

Skyryder

knowing not much about guzzi's
my italian lady doesn't like leaks either, back fires a lot if adjusted too rich or the pick ups are worn.

as "she" backfires only when hot try to lean the lady a bit (CO).

have fun

mjvduc

[XP@]

Before you muck about with anything serious (or pay a bike shop), TIGHTEN your exhaust bolts, all of them.

[Finn]

It's not your bike Skyryder. You're just getting old and loosing control of your bowels. It's you that's running rich.

[Skyryder]

It's not your bike Skyryder. You're just getting old and loosing control of your bowels. It's you that's running rich.

And to think I was begining to miss you. Now that is 'rich.' again Finn.


Skyryder

[Skyryder]

Looks like I need new header pipes. Had a real good look today. Took off the mufflers and checked the entire exhaust system. Nothing. Then I noticed a series of small pinhead holes around the crossover. This is on the same side that I had to get welded due to the crossover weld breaking a few months back. I'm picking that the heat has somehow weakened the pipe and pinprick holes have ocurred.

Skyryder

[scumdog]

Citizen Scumdog was right! (To paraphrase Blazing Saddles)

An exhaust leak WILL cause backfiring (although normally the leak is up nearer to the exhaust port)