2013 FLHTK, stage two, Big sucker intake. I've been chasing my tail for over a year trying to figure out why I get this clattering/clacking noise coming from my engine once it warms up. When I leave my house after starting it and I'm just idling out of the neighborhood, the bike is smooth and quiet. Then I get about a block down the street and it starts to clack at idle.

To make a long story a little shorter I finally isolated the noise. It's actually coming from the throttle butterfly plate...WTF? When it's stone cold it's quiet but as soon as it warms up it starts to clack with the beat of the cylinders. When I open up the throttle a little above 1500 RPM it stops. Riding along I don't hear it and even decelerating at stop lights I don't hear it. But...As soon as I come to a complete stop and come to a stable idle, it will start to clack.

I had to pull the air filter off to see in there and figure out what was happening. While I sat there and watched it, the throttle plate is bouncing back and forth as if it were opening and closing at a rapid rate. The plate may only be moving about 1 degree or so but it makes a lot of noise. I thought I was throwing a valve or something.

Anyone know if this is normal or a way to fix this? I couldn't find any other threads on this.

 

I'm planning to take it to the dealership on Monday to see what they have to say about it. I'll let everyone know.

 

Here's what it sounds like on a video I made up.


This video starts at about one minute after a cold start.

 

Durango Colorado's Harley shop manager (Slade, good guy!) contacted tech support with this video as an example. Tech support said that the combination of the high lift cams and heavy breather air filter creates a larger than normal intake suction, especially at idle. That, in combination with a METALLIC gear train that drives the butterfly valve causes some clatter at idle. The high suction causes that metal gear to move back and forth against the spring pressure. It only seems to be effected when at idle.

After I got back from the hot ride home and idled up to my driveway, the noise was undetectable. Go figga!

Good stuff to know for uninformed people that have high lift cams and stage II+ upgrades. Hope this relieves some anxiety when people notice this. Wish the hell someone had told me!