backfire issues

can anyone tell me why the swing backfires i just got mine out of the garage and rode about 15 miles all is good then the swing starts to backfire thanks ellen

Backfiring is caused by unburned gas. If the bike is not ridden very often the gas will tend to break down and not burn as cleanly. With the addition of ethanol this is even worse. A fresh tank of gas might help. It's hard to diagnose without knowing about your riding habits and the condition of the bike. Others much smarter than I will chime in. The main thing is to let them know as much as you can about the storage of the bike, age of the bike, milage since last tune up, and any other information about the problem. I've found there are some very smart people on this forum and they will be glad to help. I hope you get it running right. Springtime is coming.

We had a few days ago a discussion about this...
I think it should be normal under some conditions but not all are confirm with me...
Do you have the backfire all the time or only under some conditions like motorbraking, after fast throttle closing, etc?

Backfire is caused by unburned fuel and there are some reasons for this. You also need air for the backfire...

Do you have the Backfire outside of your silencer or do you have the "plopp" inside the silencer? If it is inside, you also need unnormal fresh Air in the silencer, here are also some reasons and one of this is also normal...

Do you have modified anything? A tuning exhaust or a sport Air Cleaner can also cause or boost this...
What is the Maintenance status? How much km/mls are on the scooter and did you (when?) adjusted the valves?

I have found this video for example

Here you can see the (in my opinion) "normal" Backfire with an "open" exhaust (MIVV) and i would bed also a non-stock airfilter

Or here another Video with a really extreme exhaust and also backfire

Hi
I have the same problem on my newly purchased SWing (5300 miles and otherwise fine, no mods, original exhaust). Happens when I rev very slightly (2000RPM) and during driving but not all the time usually when I am throttling off. Doesn't worry me and doesn't affect the bike, just curious more than anything else. In fact it kind of sounds cool. But I guess it's not meant to backfire. So i would be grateful to know if anyone has any answers to this.
Thanks
Martyn

Sound's like your driven clutch springs are holding hard forcing the motor to decompress without any slippage by the driven clutch.Sound's like a reverse hick up.You might have xcess carbon on your pistons causing pre ignition.You might take your swing for a good ride to blow some carbon out.What year is it ,how old is the gas.

"Sound's like your driven clutch springs are holding hard forcing the motor to decompress without any slippage by the driven clutch."


You guys are funny. It's caused by the PAIR valve.

Hi
I bought the bike only last week and it came with a full tank of gas which may be quite stale as the guy only did 800 miles on it in the last 12 months. The back fire is inside the exhaust and is really a 'plop' sound not the outside loud one.
Any help on what to try first greatly appreciated.
Thanks
Martyn

I know that when I have let my SWing sit that it would backfire until the next tank, and I rode it more often. That may be what is happening with you Martyn. Let us all know though if you both find the cause.

From what I understand most bikes/scooters that have emission controls installed them (air injector canister etc.) tend to do this a bit. It is MUCH more noticeable when factory exhaust is changed. My SWing does this but not much.

On the KLR forums they strip out the emission controls and the problems disappear. I have never heard this mentioned here on the Silver Wing forum so maybe it is not an option.

I agree with Glenn that this issue can some times be caused by a pollution devise and is normal.If it is excessive it can be a defective pollution control devise. Also a slight exhaust system leak(usually at the header pipe on the cylinder head) can cause clean air to be drawn in on deceleration causing this concern. Howard