I've got an 04 Fat Boy EFI and it's making a weird noise from the left side of the bike. The best way to describe the sound would be for you to imagine the sound of an air compressor running with a hose hooked up to it, cut the end of the hose and hold your thumb over the end to let the air **** out. Sorta like a pifft, pifft, pifft, pifft, pifft, very quickly. Or think of a plastic grocery bag caught up or tied up on the rear passengers left foot peg, and it flapping in the breeze. It's extremely annoying and happens infrequently. At times it's loud enough to get over the top of the exhaust (V&H Big Radius with baffles removed very loud bike!).

Now check this one out, I thought it was an exhaust leak as I noticed the rear cylinder exhaust bolts loosened up frequently. Also, it seemed ever time I tightened em up, the noise would go away. I replaced the gaskets (HD high performance) and put locking nuts on. Still, the sound! It's weird because the sound only happens at speeds at or above 40 mph and when the bike runs at 200 degrees. It would usually only happen at those speeds while I let off the throttle but is now happening during acceleration. I took it in for service and of coarse the tech took it for a ride and chalks it up as exhaust echo. Dude,,, no way! It's a sound that is not in sync with the exhaust. A buddy of mine thought I had a blown head gasket but I would think the sound would be continues regardless what speed / rpm. I would hear a blown head gasket at idle, no? Again, under 40 mph it goes away. Also, I why would I hear it coming from behind me?

Sounds like a blow off that comes from under my *** just behind and to the left of me! And no, I'm not all that gassy!

I'll tell ya, it's annoying enough for me to not want to ride!

I hope someone here can help!

Thanx in advance,

Jeff

 

Does it sound like a herd of fish spitting water at a piece of glass, but out of sinc?
Check your primary chain tension.
Ron