New sound today, not sure what to make of it.

Happens when I'm going downhill, between 15-20mph (I was on a steep gravel road), 2nd gear (allowing the engine to help slow me down/hold me back, no throttle. Using the back brake from time to time to aid stability.

The engine has been making an interesting, almost unnoticeable noise. Not a cough, not like it's missing, not pinging, but a "puff" kinda sound. I know it's not coming from the exhaust. It seems to interrupt the normal purr of the engine just enough for me to take notice. Add a little throttle, and it goes away. I can't replicate it in any other way except as described above.

I'm thinking this may be normal, but thought I'd post the question to see if anyone else has been experiencing this.

nvoelsch,

This little puff sound is a tiny back-fire. The sound is reduced by the Cat and the Muffler.
It occurs when engine braking and the throttle is still very slightly open. If you add power or let the throttle close all the way this will not occur.
Try letting the throttle close all the way to see.

If the throttle is for certain closed all the way, then you may need to adjust your Throttle-body balance. If that doesn't help then check your exhaust valve clearances.

Back-fire are normal when running very lean (some fuel but not enough fuel for the mixture). If the throttle is closed all the way then there is NO fuel so nothing to burn.

Enjoy the ride!

nvoelsch,

This little puff sound is a tiny back-fire. The sound is reduced by the Cat and the Muffler.
It occurs when engine braking and the throttle is still very slightly open. If you add power or let the throttle close all the way this will not occur.
Try letting the throttle close all the way to see.

If the throttle is for certain closed all the way, then you may need to adjust your Throttle-body balance. If that doesn't help then check your exhaust valve clearances.

Back-fire are normal when running very lean (some fuel but not enough fuel for the mixture). If the throttle is closed all the way then there is NO fuel so nothing to burn.

Enjoy the ride!


Is the exhaust stock? If not you may need to adjust the FI.

Even simpler is how much fuel was in the tank at the time? Going downhill could mean your fuel sloshed forward and was having a hard time getting out of the tank and running lean.

Maybe it's the air injected by the PAIR (Pulsed Secondary Air Injection) in the exhaust ports under engine braking. It's there to protect your catalytic converter. I removed it before I even tried the Versys to reduce backfiring tendency with a low restriction exhaust slip-on and header.

Some good ideas, thanks guys. I'm going to try it again this weekend and take my helmet off to listen closer (eeek!). These Shoei's don't let you hear much.

The gas tank was slightly more than half full. I'll try it with a full tank. Let y'all know what I find out!