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.:)

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. :cool:

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?

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.

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?

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.

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.

Re: Back firing, flame sout the exhaust etc, where do I start looking?
 

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!

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'

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??

http://img695.imageshack.us/img695/6750/wires001.th.jpg

Re: Back firing, flame sout the exhaust etc, where do I start looking?
 

TRE mod. Slightly different ignition map depending on gear position, nothing to worry about.

Re: Back firing, flame sout the exhaust etc, where do I start looking?
 

Cool, ta.

Re: Back firing, flame sout the exhaust etc, where do I start looking?
 

Just been out and pulled the front plug cap off and started it up with a plug in the cap and it has a big strong spark.

I've ordered some new plugs and will fit them thursday as a matter of course.

I'll also strip the carbs and give them a clean as I'm now wondering if its something like a blocked pilot/slow jet? I did drain the float bowl but it didn't solve anything.

But I'm also reminded of my old SV which displayed similar symptoms and it was due to the internal drain (which runs from the filler cap through the tank and out the back) rusting through and letting water into the tank and subsequently the carbs. That only ran on one cylinder until I changed the tank and fuel. But the drain does seem to blocked at all, so hopefully a carb clean and new plugs will solve it.:)

Re: Back firing, flame sout the exhaust etc, where do I start looking?
 

Hmmm I don't suppose this would help, but would it be the cause?

http://img836.imageshack.us/img836/9760/stub001.jpg

Re: Back firing, flame sout the exhaust etc, where do I start looking?
 

That'd do it!

Re: Back firing, flame sout the exhaust etc, where do I start looking?
 

I hope that is it as jets are clear and choke plungers free etc. Of course its absolutely pouring down now and I've had to retreat inside and leave the bike undercover! Damn this bloody rain I want to get it back together and fit the new indicators etc and get it ready for the MOT. Typical that I take the day off to work on the bike and it turns into monsoon season!:rolleyes:

Re: Back firing, flame sout the exhaust etc, where do I start looking?
 

You were on the money as usual Chris! Put it back together and cranked the fuel though and straight onto two cylinders!

Its not running perfect but I expect that plug isn't what it could be. I'm waiting on my new plugs and hope that will cure it completely. Dunno if you'd even notice it to ride but at a constant throttle you can just hear its not quite 100%.

Float bowls were very clean and the chokes had been out recently so I guess they'd been chasing this and just missed the little plug?

Got some new indicators and a number plate to fit and then it should be ready for its MOT. Could use a rear sprocket and a new chain is always ideal but i'll get them next payday and after the MOT.

Cheers for the advice. :)

Re: Back firing, flame sout the exhaust etc, where do I start looking?
 

Doesn't say in any of your posts that you're using fresh fuel, so completely drain the fuel tank, thoroughly flush it out with fresh fuel, then refill (with fresh fuel obviously). It's anybody's guess what's in the tank.

Re: Back firing, flame sout the exhaust etc, where do I start looking?
 

Hi Irie! Will do just that..