Sorry for the long post, but I have cured my Dyna’s vibration problem for about $10 in materials and I thought others might benefit from my approach.
I have a 2005 FXDI with a HD 95 inch Stage I kit.
Like some others on the Forum, my bike had, what I consider, excessive engine vibration transmitted to the handlebar, foot pegs, and seat. The vibration was especially evident below 3000 rpm. At idle, the handlebars jumped around excessively.
I followed the Service Manual procedure for vehicle alignment in an attempt to reduce the vibration. Alignment includes loosening (but NOT removing) ALL the motor mount attachment bolts, and then running the motor for 5 seconds during which allow the mounts to align themselves to the frame. The motor mount attachment bolts are then retorqued to spec. The procedure helped a little, but did not cure the problem. I also looked at other changes that might address the vibration problem such as “Bar Snake”, different length handlebars, handlebar mount bushings, etc. All these are Band-Aids on the fundamental problem of too much vibration.
A few weeks later I was thinking about the motor mounts and the alignment procedure and was struck by the cause/cure of the vibration problem. Any elastic motor mount, like the Dyna’s, has a limit to how much vibration it can absorb. Engine movement in excess of this limit is transmitted through the frame to the handlebars, foot pegs, seat, etc as vibration.
What struck me was that when I did the alignment procedure and the mounting bolts were LOOSE, there was a gap between the mount and the frame. Tightening the mounting bolts caused my front motor mount to be PULLED forward to the frame as the mounting bolts were tightened. I noticed that when the mounting bolts were torqued, the frame was also deflected somewhat.
THE ELASTIC TRAVEL OF MY MOTOR MOUNTS WAS LARGELY USED UP JUST BY BOLTING THE MOTOR MOUNT TO THE FRAME.
Any movement of the motor would not be absorbed by the mount – the elasticity of the mount is already used up before the motor is even started. Hence any engine movement is transmitted to the frame and is felt as a vibration. This would also explain premature failure of Dyna motor mounts – they are under stress to begin with.
My solution was to shim the gap between the UNSTRESSED front motor mount and the frame. THE ENTIRE INHERENT ELASTICITY OF THE MOUNTS IS NOW AVAILABLE TO ABSORB ENGINE MOTION. MY VIBRATION PROBLEM WAS GONE!
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Try this site for photos:
http://spotks.blogspot.com/
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Picture “A” shows the gap between the unstressed front motor mount and the frame of my bike – it is almost 0.2 inches. The solution is to shim this gap.
Picture “B” shows my test where I used washers as shims to test my theory. Result - excessive vibration is GONE. The bike is very smooth and the handlebars don’t jump around at idle.
Picture “C” shows the final result. I cut some brass shim stock to fit and used longer bolts to accommodate the shim’s thickness.
Picture “D” shows a scissors jack and block of wood I used to hold the engine up when I had the mounting bolts removed. I had my wife steady the bike and hold it level while I worked on the mount.
Picture “E” shows the shim stock I made and the bolts I used. The stock HD fasteners for the motor mounts are chrome plated, grade 8, socket head screws, 3/8 inch – 16 tpi – and 1 1/8 inches long. [CORRECTION: THE 2005 PARTS MANUAL LISTS THE BOLT LENGTH AS 1 1/8 INCH, THE MEASURED LENGTH IS 1 1/4 INCH] I obtained quality grade 8 bolts, (local caterpillar dealer) slightly longer than stock, to accommodate the shims and still retain the same purchase in the mount
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See "Thorns" great suggestion at post #30 to simplify this process.
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Some Hints:
--- Don't force shims into the gap, you don't want to create a problem in the opposite direction.
- Have a Service Manual available for the alignment procedure.
- When initially measuring the frame to mount gap DO NOT LOOSEN THE REAR MOTOR MOUNT BOLTS. You want to determine the total mount to frame gap.
- After you shim the front mount, be sure to do the alignment procedure in the Service Manual as the rear mount now will need to be able to align itself.
- Be sure to keep the bike VERTICAL when you are working on these mounts. I attach a level to the front and to the rear brake disks to make sure the bike is level.
- My bike tracks straight, I did not need to mess with the alignment adjustment under the tank.
been there, done that.
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