2000 Honda 400EX Backfires

[Trent Finnessey]

I’ve got a 2000 400ex with a dg slip on muffler, it came with he stock muffler on it but the previous owner had the dg in a box so I put it on. I’ve been riding it for the past month and a half and every time I let off it backfires, and the other day the backfires got way louder, 2x louder! I’m concerned that I may hurt my motor? Why does is backfire??? Thanks

[MarkinAR]

Check the plug, but it's probably running lean.  Running too lean can indeed burn a piston. 

[Arizona]

If it backfires on deceleration its usually rich, can try adjusting carb, 

sometimes changing exhaust requires a little re jetting,  Az

[Ajmboy]

Topic moved to Honda ATV forum and title updated to:  2000 Honda 400EX Backfires

[spock58]

Any exhaust leakage can also be causing backfires. If you didn't use new gaskets then I'd suggest you try that too.

[Trent Finnessey]

On 7/14/2020 at 11:34 AM, spock58 said:

Any exhaust leakage can also be causing backfires. If you didn't use new gaskets then I'd suggest you try that too.

An an exhaust leak is exactly what is was! Thanks for your help, and to all of the other generous people who helped me out!! 

[wwsivicww]

lean pilot....

 

[littleguy]

I did'nt know an exhaust leak could cause backfires, thanks for the tip!