Back firing, flame sout the exhaust etc, where do I start looking? - SV650.org

Taipan · 24-10-11, 05:44 PM

Hi All

I charged up the battery on the 1999 SV and started it for the first time. Took a while to start and then spluttered a bit and sort of ran on one cylinder with the other back firing badly and I do mean badly with gunshot style bangs and even flames out of the race can!

Is this typical or anything or sounds like a common fault with SVs?

I'm guessing this is something electrical? I thought I kept my manual when I sold my last SV but can't find it anywhere. So I'll have to buy another Haynes. Until I get that I dont have specs to check things for.

Any help greatly appreciated.

24-10-11, 05:56 PM

Which cylinder is it running on? My guess is it's running on the rear so any unburned fuel is being spat directly down the front down pipe. It's then getting ignited, hence the bangs. The front plug is a bit of a cow to get to, you need to drop the rad to get full access. I would certainly look at the plugs first.

As far as the popping and banging goes, even in normal running circumstances they all do it to some degree. Mine does it usually when hot. It looks pretty cool, even better with the baffle removed so you get the full flame thrower effect, especially when it's getting dark out.

My mate followed me home from Squires a few weeks ago after dark and commented how impressive it looked.

Taipan · 24-10-11, 06:32 PM

Well both downpipes were hot, or at least I couldn't tell which one was cooler?It has sat about a bit though. This is just with me starting it up and not riding it, although I dont think i'd even be able to pull away like it is as it is that bad. I've taken thursday of to have a good look at it and plan to pulll teh carbs and give them a clean and check the plungers. But with all that backfiring I wonder if its not more electrical than fuel related?

Taipan · 24-10-11, 07:30 PM

Just started it up and let it tick over. The front cylinder isn't firing at all on idle. So at least i know which cylinder is at fault.

24-10-11, 07:32 PM

Sorry for the late reply, how old are the plugs and have you got a fender extender fitted?

Taipan · 24-10-11, 07:35 PM

I've only just bought it and it has been sitting around for a while. No fender extenda fitted and it hasn't been ridden for at least 5 months. I sprayed some WD40 up the little drain hole on the front cylinder to make sure it was clear and not full of water but it didn't solve anything.

yorkie_chris · 24-10-11, 07:37 PM

Possibly water in carb, stuck float or enrichment plunger or bad plug.

Taipan · 24-10-11, 07:40 PM

Quote:

Originally Posted by yorkie_chris

Possibly water in carb, stuck float or enrichment plunger or bad plug.

Cheers for that. I'm out there grovelling about with a torch now trying to see if I can drain the float bowl? Bloody dark nights!

yorkie_chris · 24-10-11, 07:45 PM

If it's kept outside that's pretty likely suspect.
Also likely to be a complete git to get the drain screw to move.

Personally I would pull carbs off as they could probably do with some lovin'

Taipan · 24-10-11, 07:50 PM

Yup, that will be thursday first job I think. Just having a look round ass I remember dislodging one of the LT wires off the coil on a bike once and it messed about like his until it fell off completely. Does anyone know what these taped up wires are for??

24-10-11, 05:44 PM	#1
Taipan Member Join Date: Mar 2007 Location: Basildon, Essex Posts: 785	Back firing, flames out the exhaust etc, where do I start looking? Hi All I charged up the battery on the 1999 SV and started it for the first time. Took a while to start and then spluttered a bit and sort of ran on one cylinder with the other back firing badly and I do mean badly with gunshot style bangs and even flames out of the race can! Is this typical or anything or sounds like a common fault with SVs? I'm guessing this is something electrical? I thought I kept my manual when I sold my last SV but can't find it anywhere. So I'll have to buy another Haynes. Until I get that I dont have specs to check things for. Any help greatly appreciated.

24-10-11, 05:56 PM	#2
Noddy Guest Posts: n/a	Re: Back firing, flame sout the exhaust etc, where do I start looking? Which cylinder is it running on? My guess is it's running on the rear so any unburned fuel is being spat directly down the front down pipe. It's then getting ignited, hence the bangs. The front plug is a bit of a cow to get to, you need to drop the rad to get full access. I would certainly look at the plugs first. As far as the popping and banging goes, even in normal running circumstances they all do it to some degree. Mine does it usually when hot. It looks pretty cool, even better with the baffle removed so you get the full flame thrower effect, especially when it's getting dark out. My mate followed me home from Squires a few weeks ago after dark and commented how impressive it looked.

24-10-11, 06:32 PM	#3
Taipan Member Join Date: Mar 2007 Location: Basildon, Essex Posts: 785	Re: Back firing, flame sout the exhaust etc, where do I start looking? Well both downpipes were hot, or at least I couldn't tell which one was cooler?It has sat about a bit though. This is just with me starting it up and not riding it, although I dont think i'd even be able to pull away like it is as it is that bad. I've taken thursday of to have a good look at it and plan to pulll teh carbs and give them a clean and check the plungers. But with all that backfiring I wonder if its not more electrical than fuel related?

24-10-11, 07:30 PM	#4
Taipan Member Join Date: Mar 2007 Location: Basildon, Essex Posts: 785	Re: Back firing, flame sout the exhaust etc, where do I start looking? Just started it up and let it tick over. The front cylinder isn't firing at all on idle. So at least i know which cylinder is at fault.

24-10-11, 07:32 PM	#5
Noddy Guest Posts: n/a	Re: Back firing, flame sout the exhaust etc, where do I start looking? Sorry for the late reply, how old are the plugs and have you got a fender extender fitted?

24-10-11, 07:35 PM	#6
Taipan Member Join Date: Mar 2007 Location: Basildon, Essex Posts: 785	Re: Back firing, flame sout the exhaust etc, where do I start looking? I've only just bought it and it has been sitting around for a while. No fender extenda fitted and it hasn't been ridden for at least 5 months. I sprayed some WD40 up the little drain hole on the front cylinder to make sure it was clear and not full of water but it didn't solve anything.

24-10-11, 07:37 PM	#7
yorkie_chris Noisy Git Mega Poster Join Date: Apr 2007 Location: Halifax/Leeds Posts: 26,645	Re: Back firing, flame sout the exhaust etc, where do I start looking? Possibly water in carb, stuck float or enrichment plunger or bad plug. __________________ Currently Ex Biker Now rebuilding a 63' fishing trawler as a dive boat

24-10-11, 07:45 PM	#9
yorkie_chris Noisy Git Mega Poster Join Date: Apr 2007 Location: Halifax/Leeds Posts: 26,645	Re: Back firing, flame sout the exhaust etc, where do I start looking? If it's kept outside that's pretty likely suspect. Also likely to be a complete git to get the drain screw to move. Personally I would pull carbs off as they could probably do with some lovin' __________________ Currently Ex Biker Now rebuilding a 63' fishing trawler as a dive boat

24-10-11, 07:50 PM	#10
Taipan Member Join Date: Mar 2007 Location: Basildon, Essex Posts: 785	Re: Back firing, flame sout the exhaust etc, where do I start looking? Yup, that will be thursday first job I think. Just having a look round ass I remember dislodging one of the LT wires off the coil on a bike once and it messed about like his until it fell off completely. Does anyone know what these taped up wires are for??

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