Rubbermount_EVO Knock heard and felt through handle bars

[XL_1200C]

Hello fellow Sportster Owners!
I have been encountering an occasional thunk sound / noise coming from what feels like the front end of the bike when it goes over certain frequency of road irregularities at city speeds. Nothing noted while on the freeways or open roads where the speeds are higher.

I tightened up the triple clamps (all bolts) and put the front brake on while in the garage and rocked the bike back and forth and got nothing. So it's not the triple clamp or forks. Could this knocking be coming from the rubber motor mounts? Particularly the front mount?

Is this symptom documented somewhere by another rider? Any ideas where I should be looking for a cause of this? The side stand is cushioned by the stock rubber stopper so it ain't that I believe...

Help this is annoying.

[XL_1200C]

2005 XL1200C, mileage is 22,500 roughly, Simple stage one setup with TC88A and free flowing exhaust, Mikuni Carb.

[IronHeadRon]

I think you maybe experiencing a down response because people are thinking pre ignition when you say knock (thus engine guys jump in a suspension experts ignore it)

Anyways, my guess is the brake, we got a similar experience with the ironhead and not aligning the drum correctly (by spinning engaging and then tightening to the point where it grabs but doesn't drag.

If your rotir/drums are not parallel your tire it can hit every few rotations (you can force disengage brakes too, as anyone who's changed disc's with a clamp knows so my iff the cuff guess is that at highway speeds the old it's hitting on is knocked back to quickly for you to feel it, and at low enough speeds maybe it drags the whole time?

That's my best guess, but I would try to rename thread using ap different word than knock, thud or something. Other than that I know not your bike, but I saw this was open for a while and think that may be the reason.

[Tomcatt]

Originally Posted by XL_1200C

I have been encountering an occasional knocking noise coming from what feels like the front end of the bike when it goes over certain frequency of road irregularities at city speeds. Nothing noted while on the freeways or open roads where the speeds are higher.

I tightened up the triple clamps (all bolts) and put the front brake on while in the garage and rocked the bike back and forth and got nothing. So it's not the triple clamp or forks.

Steering head bearings can do this if they're loose enough. Lift the front of the bike enough that the front tire is slightly off the ground, grab the fork sliders at the front axle, and pull/push them front to rear to see if you can feel play in the steering head bearings.

It's a much better test than rocking the bike while holding the front brake on. Plus, if they are loose you have the front tire off the ground so you can check fall away as you're adjusting the bearing preload.

[wedge]

Originally Posted by Tomcatt

Steering head bearings can do this if they're loose enough. Lift the front of the bike enough that the front tire is slightly off the ground, grab the fork sliders at the front axle, and pull/push them front to rear to see if you can feel play in the steering head bearings.

It's a much better test than rocking the bike while holding the front brake on. Plus, if they are loose you have the front tire off the ground so you can check fall away as you're adjusting the bearing preload.

I would start here, it's simple and could possibly save you a lot of time. If it feels good, I would still go ahead and do the fall away too to get that thought out of the way completely.

[XL_1200C]

OK Guys, thanks!

I'll check the brake Rotor to Caliper alignment and get the front wheel off the ground and try the steering head bearing and if it feels a bit loose torque the head bearing for a nice fall away of the front end... I'll let you know what's happening...