Out riding my 07 bob today when all of a sudden started to get a pretty loud noise from the engine accompanied by a loss of power and a change in the exhaust note (almost sounded like it was running on one cylinder)

Difficult to describe the noise but sounds like loud valve chatter which speeds up and slows down with the throttle.

Can't speak to dealer until tomorrow but wondered if anyone has any ideas?

 

Possible busted valve spring, chipped/broken valve, collapsed lifter.... all will do as you describe.

 

Bloody hell..... only done 5000 miles on it!!

 

Well, I can't say for sure... can't hear the engine from here

Here's my thoughts behind what I said though:

Things that happen "all of a sudden" tend to be mechanical in nature (broken, loose....etc). Having noise follow that event, lends more credence to thinking "mechanical".

"loss of power", so something has affected your engines power. Not firing correctly with the correct air/fuel mixture and/or compression.

"sounded like it was running on one cylinder". Same thing... only now we know it's only affecting one cylinder. If it were electronic or fuel flow, it would be affecting both cylinders. Only one affected... probably mechanical.

Then you drill down further, and figure out components can do all these points:
"all of sudden", "loud noise", "loss of power", "change in the exhaust note", "loud valve chatter" - which follows engine rpm.

Your description and 'important points', would lead me to believe what I stated. Good part is you're still under warranty.

Everybody gets a bad part every now and then. I did a tight build on a chevy small block several years ago, (bore,balance,deck,angle milled & cc'd heads,) all machine work done by the best in the area (a Coors sponsored racer at the time). 1500 miles and a broken valve spring... supposed to be some of the best springs to be had.... oh well. Sh......it happens!

 

Do your exhaust pipes have o2 sensor bungs? Are they being used by o2 sensors? Maybe one popped out? I had that happen with a plug after installing my power commander with o2 sensor eliminators. You will definitely hear a difference in exhaust note, and a loss of power. It was quite noticeable.

 

Did you just get your 5,000 service done? Did you do it yourself, or a dealer?

What you have sounds exactly what happened when the dealer forgot to put oil in the primary when I got my bike. The chain guides (whatever the technical term is) broke.

 

Exhaust flange nut backed off? That could cause all of the symptoms you listed. Don't forget to post the solution, no matter how embarrassing it might be!

 

+1 on that. My first thought was that one of your exhaust headers had come loose.

 

Thanks for the suggestions guys.
Been away working working in Prague this week (OMG the women!!!!!) but will check everything today and post my findings

 

Guess he never made it back from Praha.