When I start my bike it back fires it just started today

Approved and moved form forum helps

Timing can do it, any recent tune up?

What kind of bike, make, year, model?

Good day,

Backfiring is most often caused by a lean fuel mixture.
Your carb may have plugged jets.
Also look for any gasket leaks on the exhaust system.

It really depends on the type of bike you have and the context of the backfire.

Is the bike a single, twin, v-twin, in-line four? Street or dirt? Carbouration or fuel injection?

If it has carbs be sure to check fuel/air mix and that nothing is sticking. If it's a multi cylinder bike and has carbs, check balance (sync) of carbs to make sure the same amount of fuel is being delivered to each cylinder.

If it has FI, run a fuel system cleaner through a tank of gas and see how that does.

If the bike has sat for a period, especially with today's fuels that have a higher percentage of ethanol, you may need to flush the system. Be sure to add stabil to you next tank of fuel if the bike will sit for more than 2 weeks.