Probably a backfire. The pods are a place for the carbs to vent through. Basically the charcoal canister of the day.
Glad you got the cylinder running. You used me favorite high tech method of diagnostics.
09 Aprilia RS125 plated< blew that sum bitch up! New engine build soon. Rest in pieces sweet heart. 10/14/2016.
06 Paul Smart Sport Classic NFS ever.
08 S4RS Tricolore #081 NFS ever.
The pink Monster has moved away.
97 900SS CR
72 Norton Commando 750
03 KX60 with S4R rear shock,Honda CB350F, Hodaka Ace90, 3x Yam-YGS1, Yam-CS3 200, Vespa small frame, Gilera 106, Puch Sabre, Puch 50 Boy Racer, Benelli 250, Benelli 360, Honda CB350T, and many more.