I've seen some pretty unusual things at the heart of this sort of problem, and your specific situation may very well be among the list, but I would focus on the all the classic causes first. Tire and tire/wheel balance must always be considered, even when the tires look good and you 'think' they've been properly balanced. They are indeed the number one culprit. Most dealers and shops unfortunately don't actually balance the wheels correctly. The accepted (and quite improper) technique is to mount the tires with the yellow dot (light spot) adjacent to the tire valve (assumed heavy spot) on the wheel. You can take a look and see if this is the case on your bike. I questioned this many years ago and have routinely checked to see where the 'actual' heavy spot is on any wheel and the fact is, the tire valve has absolutely no bearing on the matter and is just as likely to be the lightest spot on the wheel. I know this is a little complicated, but the results can be significant. If the tire's and wheel's heavy spot wind up coinciding, the result will be too many wheel weights, but when they wind up being 90 degrees, or so, apart you'll wind up with some pretty serious dynamic balance problems. The reason so many folks continue to do this incorrectly is that most service manuals specify this. It is a hold-over from the good old spoke and steel wheel days, when the tire valve's weight was actually the deciding factor. I have corrected many wobble demons in just this way. It does mean re-mounting the tires so you may want to hold off until the next set. You may also have to explain the facts of life to the service department because they probably won't have any idea what in the heck you're talking about.
Have you checked the steering head play? The problem here, even with a new machine or perhaps especially with a new machine, is that clearances can become excessive quickly as the grease gets worked in.
You mentioned that the wheel alignment was OK, buy exactly how was this checked?
So many times the problem winds up being one of those things that the owner looked at and has assured me that it was OK.
DL, first off thanks for the highly involved reply. The tire and wheel balance issue will have to be worked out. First, I had my trusted mechanic balance my wheels and check the alignment, next my bike is a '95 so it's not the grease settling, I checked the play and it is normal. I do have a very new front tire, and I've noticed the wobble only since I've gotten it, but was thinking it might only be magnifying the worn out shock. So at the heart of all this is, should my shock be worn out by now, and would this cause a wobble?
I think the key is your statement that the problem followed the installation of a new tire. That is why I automatically questioned the balancing method. The failure to first determine where the actual heavy spot on the wheel 'before' mounting the tire can lead to a very unsatisfactory dynamic balance. I have many times corrected severe headshake and wobble by properly balancing the tire/wheel assy. My first exposure to this occurred many years ago when I was mounting a new tire. I didn't have a very good selection of wheel weights so I decided to simply use two large weights and simply place them equal distances from my mark and then just move them together or apart until a perfect static balance was achieved. It balanced easily and I thought I really had something. Why doesn't everybody do it this way? Well I found out just as soon as I took the bike out on the road. It was almost laughable, it shook so bad. I wobbled back home and rebalanced using a single (hand cut) weight this time. Smooth as glass. Why didn't the dual weight idea work? The answer is too long to fully describe here but is has to do with dynamic problems resulting from multiple corrections and influences of uneven weight distribution around the wheel. When a tire is positioned using the valve on the rim as a locator you are essentially recreating the situation the situation I outlined above. The result can is a tire/wheel assy that may be quite good at one speed and terrible at another. The end result can be any number of tire or handling problems, depending on other factors. Usually it’s the result of several problems.
The shock itself cannot be the cause of your problem. Even if it was way too soft or even replaced with a strut, the bike should not experience any sort of wobble. It can, however, add to stability problems under certain road conditions. If I had your bike in my shop, I would re-adjust the steering head, check the rear wheel's alignment relative to the front, and check the front fork adjustments. All that failing, I would then go more deeply into the forks and swingarm and linkages. It sounds a little as though your giving a clean bill of health to some items needing a little more thorough examination.
A steering damper, at this point in time will only serve to camouflage the problem. You're correct in that it might even be satisfactory for the time being, but you really need to correct the fundamental problem first. If you don't you risk premature tire wear, uneven wear, or a number of other unpleasant things.
Ninja's idea may well be a good one, but not right now.
Don't worry, I'm not getting a steering damper, because the front has NEVER shaken one bit since I've had it. My giving a clean bill of health to certain areas is only my passing on of what I've been told about things which I can't personally verify. I certainly can't balance my own wheels, and if I can't trust my mechanic(the only one I have truly trusted in many years of dealing w/different ones), I guess I'm just screwed. Nice to know it isn't the shock since I lost my bid on ebay
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