2006 FXSTS with 36000 miles. About 500 miles ago I noticed a knocking noise at idle. Open the throttle and just off idle the noise goes away. When the engine is up to temp and at a low idle I can actually feel a knock in the handle bar.
Now I've experienced a rod knock in an automobile engine - no banging at idle but put it under load and it will bang away.
The noise in the bike is just opposite that. The noise is present at idle, but off idle the noise is gone. If you get it moving in 1st and then shift up to 3rd or 4th and open the throttle wide it just labors and pulls like it always did. No knock.
Anyone have any suggestions? Am I looking at a tear down or is there something else I haven't thought of?

 

What has been done to the engine?

Did you do a compression & leakdown test? Have you checked the crankrunout and made sure it wasn't over .00... .012" ?

 

Put a real mechanics 2 ear probe stethoscope on it. (all over it). If it's really tapping from something too loose, it will let you know. These all roller engines can make noise and still be fine. The uneven firing order just rattles steel on steel and you can hear it. Does not mean it's too loose. I would sure not tear it down for that if it sounded fine at speed. You say like it always did to " If you get it moving in 1st and then shift up to 3rd or 4th and open the throttle wide it just labors and pulls like it always did" I would not be doing this too it a whole lot. If you do, it just may have a lot of wear on the big end of the connecting rods. The small end is a bushing and it's V shaped. It has more surface on the bottom side. It can actually turn doing what you are doing. If it does, it will start tapping when it contacts the piston since there is not room for it at the maximum rod angle.

 

Check exhaust bolts at manifold. Re-align header to exhaust port, re-tighten to specs
Check for carbon buildup on pistons, use a can of Seafoam spray through your intake.

 

Don't freak out yet. From the described symptoms, I doubt it's a rod knock. The rods are on roller bearings, so if it had got to the point of knocking, it would self destruct in very short order.

Because these thing shake, check on the stuff Ripsaw and PeterV points out, plus engine mounts and anything external that might be hitting against something else.

And then, drain the oil and cut the filter open to look for shrapnel. If a rod is really knocking, the filter will be loaded with metal particles. If there is metal in the oil, start with the cam chest first to see if the inner cam bearings are going away.

 

All good suggestions. One thing that came to mind. What is your idle speed? A friend had a slight knock at idle and it turned out his idle speed was too low. If it's too low, you'll not get enough oil pressure and that can result in a knock..

 

My experience with rod knocks is that if you raise the revs gently to about 2500 rpm in neutral just sitting there and let go of the throttle as the motor decelerates you will here a rod knock if there is a loose rod bearing.

 

I just had the same issue, it was my compensator, it was loose and needed to be tightened. Get yourself a primary cover gasket and some locktite. Remove bolt, apply locktite and retighten. Your welcome.

 

Yep The compensator nut is just loose. You didn't hurt anything. (And I reused my primary gasket.)

 

If it turns out to be the compensator bolt, there's a little more to it:
Remove bolt. Clean both inside and outside threads carefully, using a thread chaser on the internal threads if necessary to clean out all prior locktite (you don't want the bolt to bottom out on old Loctite). When reinstalling, use the tightening procedure in the latest service bulletin, which is quite different from just taking it up to a certain reading on the torque wrench.