FE570 backfire

NKW570 · Sep 2, 2009

Hi,
I hit a rock the other day, see pic, quite lucky i guess.

There is a quarter inch dent about 1" diameter behind the carbon shield and the bike now backfires a lot.
I loosened off that section of pipe at the sleeve and unbolted at the head and noticed the seating is distorted between the bolts and letting air out, so i siliconed both sides of the gasket and tightened up. It still backfires. Anyone any ideas?
Could it still be air escaping ? Or would the airflow be disrupted by the dent and thats causing it?

Cheers,

Nick

tazer · Sep 2, 2009

Hi Nick,

That looks a bit nasty!!

If it is popping when you back off you may find that you now have a leak where

the pipe bolts to the head, you could have bent the pipe in which case you will need

more silicone.

Steve

DaleEO · Sep 2, 2009

I don't think it's a matter of air escaping as you put it, rather under decel fresh air is getting in and that's causing the ignition of unburnt fuel in the hot exhaust.

Also, if you have an air leak there and it's pulling in air, that's right before the 02 sensor, so it might be trying to put in more fuel making the problem worse-that's just a guess.

On the header to mid pipe joint, there is some kind of a packing or gasket, and the hit may have damaged that too.

Either way, the pipe is probably bent, and there is still an air leak. You may have to replace that section of pipe if you cannot determine where the leak is at. That was quite a hit, did a nice job on the brake pedal as well.

Hair · Sep 2, 2009

Where is the O-sensor mounted on the 09s?

CodeMonkey · Sep 2, 2009

Technically, that isn't a 'backfire'. A backfire is when you get an ignition or spitback up through your fuel induction (carb or EFI).

What you are seeing is what Dale explained, because of any air leak there is suddenly oxygen mixing with hot unburned fuel in the header and you get a bit of a pop. Fix the leak(s) and you're probably fine. It's not the dent - not enough to make that much of a difference. The may require new header sections if they are warped enough by the impact to not fit together snuggly.

Hair, the O2 sensor is mounted just above where the pic shows the exhaust pipe, so it is downstream of the leak.

DaleEO · Sep 2, 2009

FYI There are no 02 sensors on the 2010's.

NKW570 · Sep 2, 2009

Thanks guys,
It has distorted the seating metal between the two bolts giving a 2mm gap at the centre of where its arced looking from the front. I dont think i can rectify this as the pipe stops me using a vice. I will pump some more silcon on both sides of the gasket for now.
Hey Daleeo, luckily i followed your tip fo lowering the foot pedal, otherwise i think the clutch cover would have been holed.

Cheers,

Nick

DaleEO · Sep 2, 2009

NKW570 said:
Thanks guys,
It has distorted the seating metal between the two bolts giving a 2mm gap at the centre of where its arced looking from the front. I dont think i can rectify this as the pipe stops me using a vice. I will pump some more silcon on both sides of the gasket for now.
Hey Daleeo, luckily i followed your tip fo lowering the foot pedal, otherwise i think the clutch cover would have been holed.

Cheers,

Nick

A suggestion..........

Take the header off and put the end that goes into the motor on top of a piece of wood at the edge of a bench with the header hanging down towards the ground. Either you or a mate might be able to use a suitable drift and mallet to drive the sealing flange back down enough to get rid of the gap. The piece of wood should take the impacts of the mallet blows to keep it from getting dinged. Or you could use this as exuse to buy one of these:

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