Help...going riding tomorrow but bike is backfiring!

Can someone please tell me why a bike would backfire? I have a 2004 YZ450F with about 5 total hours on it. It just started to backfire and I'm not sure why a bike would do this...any help would be greatly appreciated. :)

Can someone please tell me why a bike would backfire? I have a 2004 YZ450F with about 5 total hours on it. It just started to backfire and I'm not sure why a bike would do this...any help would be greatly appreciated. :)

Just started???

How does it run otherwise?

What were you doing, or how did you "make" it backfire?

Does it do it w/ the throttle off, on, low rpms, high rpms, in gear while riding or just on the stand in the garage?

Sorry for all questions and no answers but...

We need more information to help you with your backfire problem. Did you recently put a new pipe on or recently work on your carb., install a clean air filter? Like Hick asked when does the backfire happen?

Sorry guys....

It backfires when I let off the throttle (in all gears). And yes, it just started happening. This bike is bone stock, no new parts at all. I have not tuned anything on it since I bought it, including the jetting/carb. I am totally baffled by this...

Check your hot start lever. Make sure it is adjusted right and not sticking.

Will do, thanks!

i'm not sure what the exact reason for your backfiring problem is .. but it could be a few things. gas turned off or not fully in the on position ,mot likely this will cause the bike to backfire or pop. it's probably the jetting.. check those things out and good luck .

I'll almost guarantee it's a problem with the hotstart...

Pull the plunger and lubricate it and then reinstall it.

I screwed mine up once and got the same problem you describe. I reseated it and all was fine. :)

Yep...it was the hotstart lever. I had to hold the housing and push the hotstart lever all the way back before it would shut the valve. When I released it after using it, the lever would go back up but underneath the rubber cover, the housing would move but not the cable inside of it. I hope that makes sense. Once I lube it up it's been great.

Man I love this site.

Thanks everyone!! :):):D

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