The plastic cap fastening the "choke" cable to the carb casting is hardly a $ 70 part.
When replacing, you might consider a MadStad (Stead Engineering?) metal part; will cost you about half that; the plastic OEM replacement, much less, if I'm not mistaken.
KLR 650 Alloy Starter Choke PLunger. 1986-present day-KLRACP - Stead Engineering
Conceivably, an air leak through the STARTING ENRICHER (vice, "choke") system could produce a lean mixture resulting in backfiring, I'd think, although I defer to experts on the question.
Some "pyrotechnics" upon deceleration isn't unusual, or harmful; the air cut valve/backfire preventer/coasting enricher is explained in, "Care and Feeding of the CVK40," hosted on this website. Adjustment of the fuel screw can reduce "backfiring" sometimes.
Last edited by Damocles; 03-27-2017 at 06:34 PM.