Mine used to load up when idling for a long time because the oil pump was hanging up and not returning, but it never backfired.
Backfiring could be reeds like said above.
I wouldnt try and drill it, they are hardened and you will have a bitch of a time.
Just get a heavy wall piece of small diameter pipe just make sure the ID is just smaller than the bold diameter. Cut it so a few inches stick out past the clutch and get a stick welder and weld it on the inside...
I am hearing conflicting things about the weight drop on the 2012-14 HCR 800.
I know on the standard M series they eliminated the rear heat exchanger and some other stuff and managed to drop something like 20 Lbs. Now on the HCR the rear exchanger was never there, so how much did the 2014...
1993 Bombardier BR400 + and spare parts machine for sale - HCS Snowmobile Forums
Here is a link to a club in Manitoba selling one with a spare parts machine.