Motorcycle Repair: Honda VTX - Consistent vibration at 30mph.

Question
QUESTION: Hello Lazaros, I hope you can help with this issue.
I have been chasing down the source of a vibration for the past few months but to no avail.  I hear it from the front, I can feel it in my right floorboard and sometimes it feels like it’s migrating to the rear. It occurs at 30mph, and ONLY 30mph. It is consistent. If I ride at a steady 30mph, the vibration continues the entire time at that speed. The noise is loud enough to be heard on an iPhone video.

The bike is a 2005 Honda VTX 1300 cruiser, shaft drive, liquid cooled, with 55K miles. Two slow speed falls, once on each side. Both times with minimal damage (the bike or me).  Unfortunately I cannot pin down the start of the problem to either fall or any specific change.

The vibration happens when…
- Accelerating, both with and without the front or rear brake being applied.
- Whether in neutral or in gear, and with the clutch lever pulled or released.
- Handbags on, or off.
- Windshield on, or off.
- Light bar on, or off.
- With the tank mounted speedometer housing on, or off.
- Chrome radiator cover on, or off.
- “Plasti-chromed” cylinder trim on, or off.  

I’ve also attempted the following mechanical remedies and have properly torqued all bolts.
- Jacking up rear wheel, varying throttle does not recreate the noise.
- Replaced all brake pads, cleaned and lubricated calipers & pistons.
- Rebalanced both front and rear tires.
- Replaced front wheel bearings, greased axle, re-seated the forks in their “natural” positions.
- Inspected rear wheel bearings (smooth), dampers (fine), flange bearings (smooth) and final drive to rear wheel gear (clean and smooth).
- Sprayed undercoat inside my headlight bucket and securing all wiring.
- Removing and securely reinstalling stock exhausts, replacing the crush, muffler, and crossover gaskets.
- Increased space between the metal brake line and radiator housing (they were touching).

I have NOT yet, but intend to remove, check and/or replace the
- Steering neck bearings
- neck & side cover trim
- fork oil & seals
- engine mounts (access is limited)
- verify all spark plugs are firing

Here is a link to diagrams for my bike
http://www.ronayers.com/oemparts/#/l/hon/5053fd10f870021c54bea5bd/2005-vtx1300c-

Thank you Lazaros, for any guidance you can offer me.

ANSWER: Hello Peter,

Most critical and prone to produce vibration, are the engine mounts.
First deal with this.

Does the vibration occur at 30mph with top gear or with any gear?
Is it proportional to the sound of the exhaust (same frequency)?

Is it possible that the problem started after servicing engine?

Tighten engine mounts, and get back to me with answers on the above questions.

Good Luck and Best Regards,
Lazaros.   

---------- FOLLOW-UP ----------


Upper Steering Bearing   QUESTION: Hi Lazaros,
I had not reported back yet because I still have my bike on the lift, replacing the steering bearings and fork seals. So far I have found the inner race of my upper steering bearing was, in my opinion, worn into a rounded corner. The fork oil was thick and black. One fork had very little oil.

Regarding the vibration - I also found the steel support for my right floor board (where I felt the vibration) is bent, quite likely from the fall mentioned earlier. It had gone unnoticed. That support is rubbing against the floor board enough that it stiffens the vertical free-play. I will not know until I reassemble the front end but this is my "primary suspect".

Answer
Hi Peter,

The floor board support, IS a primary suspect as you very well mention.
The same applies to ANY metal part on a V-twin that touches another, without being bolted together or without any kind of silent-block or rubber between them.
That goes for the engine mounts too, as we already made clear.

Regards,
Lazaros.