96 Challenger Backfiring and Low Max RPM

[jettag]

This is a re-post with added info - Thanks for your assistance.

I purchased a 1996 Challenger with a single 787 Rotax about a month ago. This past weekend the engine started to backfire and the RPM's would max out at about 5500. Maximum speed is also now about 25 MPH and it has a difficult time planing out.

I took of the spark arrester to take a look at the carbs and the rear carb is much darker than the front carb. This is also the carb that is backfiring. At idle backfires about every five seconds or so with just a "POP". At higher RPM's (in neutral) the backfiring still occurs about every 5 seconds but there is a small flash of fire out of this carb.

I did replace the plugs, but the situation is still occuring.

Any advice from the forum is greatly appreciated! Thanks

 

[kustomkarl]

Have you replaced the Gray fuel lines? It sounds like a fuel problem. I wold remove the carbs and clean them being careful not to damage or tear the diaphragms in the carburetors. The engine needs the spark arrester to keep it from firing back through the carb and causing a fire. You shouldn't run it with the sparkarester and carb. cover off it.

Karl