Ktm backfire on deceleration

[dynafxdx79]

Hello all, I'm new here from Napa Ca USA. I've recently upgraded from my crf250r to a 06 ktm 450xc. Is it common with most ktm's to backfire on deceleration? Or do I have to play with the air fuel mixture? Thanks in advance. This is by far the best group I've come across.

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[AllanB]

Aftermarket muffler fitted? Check al is tight and run a smear of silicone around the join to ensure it is sealed.

Or it's running lean .....

[slofox]

Many years ago I had an Ariel that did that.

In this case it was an air leak in the intake manifold (had a carburettor). But as said above, it can also be the muffler seal.

[Thaeos]

Might be the air filter causing it? Happened to me once when I replaced an old one.

[haydes55]

My old KLX300 backfired as well.... I didn't want to try stop it back firing!

[gjm]

20-something years ago I had an XT550... Racing wets, big bore kit, hot cams, etc... Think supermoto, but a few years early. It backfired on over-run.

Turned out fuel was getting into the exhaust and igniting there. Thought it best to get that sorted.

[pete-blen]

Mr Yamaha has made the XT660s back fire on a trailing throttle... AIS "Air Injection System"
Is basicly a controlled air leak into the exhust pipe to burn any unused fuel the enters
the pipe...clean air shit and all that...

AIS is prob a bit high tec for a old KTM.....

[Tazz]

20-something years ago I had an XT550... Racing wets, big bore kit, hot cams, etc... Think supermoto, but a few years early. It backfired on over-run.

Turned out fuel was getting into the exhaust and igniting there. Thought it best to get that sorted.

I have a pic of what happens when you don't sort that out quick enough...



That's after closing it up a bit with the car jack too haha.

You'll undoubtedly smell it if it is running rich though.