Could be a few things. Possible to be the CDI box or the Stator.
Many things can cause a snowmobile engine to back fire. Ignition coils ( spark plugs, coils) or water in fuel. Check these and maybe it will solve your problems.
Ngk BR9ES
Clean plugs new ones maybe new points
I need more info make , model , engine size.
.028"-.030"
Use your spark plug wrench to adjust your rear suspension
simple,design,it doesn't effect cylinders that are not on compression ,it allows single spark controll
go to ngk.com type your model in and they will tell you
It may be that the spark plug is dirty. Try cleaning it
heat causes pressure, pressure causes friction, friction causes spark, spark causes KABOOM! all in a split second
i took my arctic cat for a ride went maybe 60 mile ran good then two days after went out to start an wont start an no spark
on a snowmobile all you do is take out the spark plug, take the bolts off of the studs and take the head off