brother just got 06 fatboy 15000 miles...1 cylinder didn't have spark...seemed weak...now neither cylinder has spark...where should we look for the problem?

 

A question like this suggests minimum knowledge, trouble shooting skill and equipment. What have you done to verify no spark? The shade tree, easy check is to remove the air cleaner and squirt a little gasoline or starting fluid into the intake and crank the engine. If it fires a couple of times, you have spark, but no fuel. If it doesn't fire at all, your diagnosis is probably correct. That involves the coil, primary and secondary connections to the coil, and coil wires to the plugs, perhaps even the crank position sensor, if so equipped. If you don't have at least volt/ohm meter, take it to a shop.

 

Shade tree way to check spark is turn bike over with plugs resting on jugs, may need shade to see.

Assuming bike turns over not starting circuit. Pull coil and ohm. I have had intermittent coils with good spec ohm.

I'd probably first try new plugs, if oiley. If you don't have lots of skill or patience chuck coil at it. Its 13 years old anyways. Though could be other stuff too.

Since you don't know your alphabet don't know if carbed or fuel injected.

Not sure why anyone would waste time dumping gas in , if no spark

 

" Not sure why anyone would waste time dumping gas in , if no spark"

Simple, easy test not even requiring removal of the spark plugs, but start where you are most comfortable.

 

If there is no spark it is a waste of time dumping gas in.

If you dump gas in before checking spark, you don't know if spark or fuel is problem.

You know nothing if it doesn't start. Same as before you dumped gas in. I suppose you get lucky and it starts you know it's fuel.

Myself, I'd check for spark first. He did and said it had none. So it is a waste of time.