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Check the tire pressure, tire condition, wheel bearing sideplay, and neck bearings.
The adjustment on the front end fall-off as described in the service manual is mumbo-jumbo to most folks. Here's a different way to check it I found on another forum awhile back. Guy who described it is an old time HD mechanic.
Jack the front end of the bike off the ground. Tighten the adjusting nut until the front end is hard to turn. Next turn the handlebars back and forth, from stop to stop, through several cycles. Notice the front end becomes easier to turn. Back off the adjusting nut to a slightly loose fit, then tighten to about 9 ft-lbs torque. If the front end still wobbles after this (tire pressure good and tire in good condition, with no cupping, etc.) and the wobble occurs during deceleration, tighten the adjusting nut a bit more.
If you get a shimmy and more tightening does nothing to help, then suspect that the steering head bearings have shifted and the races are no longer parallel to the axis of the steering head. This is not unusual in HD bikes as they are relatively heavy. Modern bike head bearings tend to shift back and forth in the frame, especially on the heavier bikes, and this causes the bearings to become non-parallel. Any free play in the head bearings will compound this situation. This sets up torque forces that constantly try to correct themselves resulting in a shimmy, or head shake. The cause is not looseness; the bearings have shifted, and things ain't parallel. Pull the front end off and try to reseat the races in the frame neck.
Check the head bearings frequently IAW the service manual. Since these bearings do not move around like those on an axle, they tend to stay in one spot in relation to the race. Therefore every blow on the front end from road conditions tends to flatten the individual rollers or ***** ever so slightly. Over a period of time these flat spots can cause a condition whereby you point the forks straight ahead, and they tend to fall back onto the flat spot, causing a weave as you go down the road. If tightening the preload does nothing to correct the situation, suspect flat spots in the neck bearings.
By Alpha Samuel
I had to go to about 15 - 20 foot-pounds on my Sloptail. And I added a grease fitting to the neck post to help keep fresh grease in it.
While I had the front end off to replace the cups and bearings I drilled the neck post on the left side, halfway between the top and bottom. Installed the new cups, packed the bearings as usual, and put it all back together. Then I used the grease gun and filled the neck thru the zerk fitting until grease just started coming out past the dust covers. About once a month I lift the front end up and squeeze a bit in there while moving the bars from side to side, and feeling for anything out of the ordinary.
I had the same problem with my 03 FXST. After checking everything that has been mentioned the problem still didn't go away. My wobbles were coming from loose spokes on the rear wheel. I checked them with the bike on its stand but because the weight was loaded on the tire they all seemed tight. I found them by having the bike on a lift with no weight on the rear tire. I could actually move it 2-3" left to right. Because there were so many that were loose the whole rim needed to be "trued" again. The dealer wouldn't cover this under warranty (don't need to get started on that subject) and was willing to complete the job for around 300.00 without a gauruntee that it wouldn't happen again. So I rode the bike home, went on E-Bay and found a set of Fat Boy OEM wheels that I picked up for 400. The Bike looks better, I don't have to worry about loose spokes again and all I need to get home is a can of fix a flat.
Lee, thanks for bringing the rear wheel problem up. I'd forgotten about that possibility. I replaced the rear wheel on my '87 FLST with the mag rear wheel off a '92 Sporty. The original wheel was out of round and probably contributed to the low speed wobble I had on a couple occasions.
Thanks for the info, I'm going to check that out as well. I did notice that when I had her on the lift yesterday, and noticed a very slight tweak in the front rim. So I suppose that could be the culprit along with maybe the rear wheel as well.
I noticed the "Duck waddle" when lightly holding the grips at 40 mph. Only has 500 miles on it and already told my dealer, just waiting to get it checked at the 1000 mile service.
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