05fatboy tc 88 with carb. today i tried to repair the backfire and bad running of my scoot. i drained the fuel, replaced the filter, put fresh gas in and octane booster. i replaced the spark plugs. replace the intake seals.(as i though i had a intake leak. but bike still runs just the same. like crossed plug wires on a car engine. i am thinking that it has ingnition box problem, or maybe crankshaft sensor. does anyone have any experience with these components.no way to test ingnition box execpt to substitute. is there a measurment that can be made to test the crank sensor. very are thes expensive parts, and are there better aftermarket ones, if i have to replace them i might as well upgrade. very fustrated. any advice would be apericated

 

You can at least verify that it is (or isn't) an ignition problem for maybe $14.99 or less. Get one of the cheap nearly useless neon timing lights that you often see on the bargain table at the autoparts chain stores. What you need for this is the cheapo unit that has a coiled up neon tube that connects in series with the sparkplug and has no 12 volt connections. Watch the flashing of the light and see if it's steady when the engine misses. If it is, your ignition up to the sparkplug is OK. With practice, you can even spot bad plugs.
Even if your problem turns out to be in the ignition, chances are good that it is a coil or bad wiring connection causing it.
Be sure to take a close look at the battery cable connections at both ends, especially the ground. If a battery cable is rattling around and occasionally losing contact, the resulting voltage spike can cause the igniter electronics to reset and miss a beat or two.

 

Did you try replacing the plug wires?

 

Tex
Is it backfiringoutthe carb or out the mufflers??

 

battery connections good and clean, took out battary and cleaned good although it wasnt dirty, all ground conections i tightened and cleaned.. hey canuck, it is backfiring through both the carb and exhaust. bike only has 4000 miles on it. but not under warranty.. very puzzled

 

clean connections at the ign. module.