Wonky steering at high speed

[scoot]

I just read thru wingnuts's thread on the steering damper, and it's got me thinking about my own steering issue. It's been going on so long that I have gotten used to it, but maybe someone has a fix.
History: Bought this still- nameless 80g w/ Vetter fairing & hardbags in '06. Found that the bike's steering would seriously wobble starting at 90mph, my impression was such that I expected it would increase into a tank slapper. Having gone thru that scenario 20 yrs earlier, I know how that ends up. So I slow down, cars routinely pass me, I buy and install a TKAT brace. Better. Can get to 105mph (hypothetical) before it hints of a wobble. Pretty tolerable, I judged it "problem solved".
Then I shelved the Vetter fairing and it's bracket. Replaced it with one of those clear Lexan fairings that mount to the handlebars. It extends to below the turn signals and also blocks the handgrips. The wobble shows up at the same 105, but seems more pronounced. I installed new tires. New steering head bearings. New Progressive heavy duty fork springs. No air in forks. Stock rear shocks. About 47K miles on the bike.
It feels like what a kite trying to fly with no tail looks like. The original wobble felt like it came from the road up, now my impression is the source is this lighter fairing.
I was thinking to add a steering damper, but that's a bit off track without first experimenting. Remove the fairing and make a run. Maybe reinstall the vetter?
My objective is to be stable enough to feel like the bike is running on rails at 110. Anything faster is just too fast for me anyway.
Anything else to try, or measure, or?

[motoman]

Lots of variables there not seeing the bike and limited information. Swing-arm bearing adjustment, tire pressure, rear shock settings and condition have alot of effect on higher speed handling situations.

[scoot]

Thanks, motoman. Interesting that you're looking at the back of the bike. The swing arm bearing is something I never looked at. It's an arm, it swings, it gets grease in the zerk fitting each year. Now I'll need to learn more about that. BTW, I'm lately running 35psi front, 38psi rear. I have seen no obvious frame issues, and the forks are as parallel as I can quantify. Oh, and the rear shocks are set at #4 on the little dials on top, and the stiffest setting on the bottoms.

[TADracer]

Check everything...wheel track, bearings in swing arm and steering head and anything that can catch wind condition of tires and balancing. If you can, even verify the steering head angle to the rest of the bike incase something there is off from the factory. A little thing can cause it and sometimes is hard to find. Installing a fairing, wind shield or even a small bug shield type windscreen requires some tuning to 'throw the wind' without acting like control surfaces on an airplane.

Concerning a steering damper, they are useful but it will not solve your problem, only perhaps lessen the symptoms due to the dampening effect though I do use one on my machine.

[rover]

wobble

Try lowering your rear shocks, like the middle notch on the bottom. The higher the rear, the steeper the fork angle. A steep fork angle will have more tendancy to wobble. Look at the old school choppers, at that angle, they steer like on rails, and take some muscle to turn. Mine has never wobbled, but when I raise the back (I have air shocks) the bike steers so easy it scares me.

[mack]

Tracking

Sounds like it's not tracking right. Wouldn't be a factor or detectable at lower speeds. Have you checked to ensure the swing arm is centered in the frame and center of rear wheel aligned with the front wheel.

[natemoen]

And just an FYI. That grease zerk on the swingarm is pointless. The bearings they are talking about are at the front is the swingarm under those chrome side caps.

[motoman]

Like stated, alot or combination of several factors can cause a high speed "weave". Fortunately my Venturer even with the Yammy tail trunk tracks straight up to bout 7800rpm, after which the mph come real slow at 5000ft.elev. having the whole "barn door" on the front with a 25in. windshield. To avoid any excessive tire cupping on the front and better front-end handleing should be running the max. tire pressure reccomended o tire sidewall anyways which I'm betting is 42psi. Same for rear. Other than everything suggessted, I don't advise making a habit of running these scoots over the ton......ageing frames and normal metal fatigue associated with the flexing, vibrations and heating and cooling off could lead to an ugly "get off" or at the least a high speed weave from a dip in road upsetting handleing geometry that may be difficult to get back under control. Understand your concern as it would be comforting to know that the bike is not going to go "array" on you due to a mechanical oversite.

[rover]

Awry

is the word

[ThrottleJunky]

..I don't advise making a habit of running these scoots over the ton......ageing frames and normal metal fatigue associated with the flexing, vibrations and heating and cooling off could lead to an ugly "get off" or at the least a high speed weave from a dip in road upsetting handleing geometry that may be difficult to get back under control.

I don't even like to think about a "get off" at high speed. Ugly.

[cywelchjr]

Another thing to remember, any fairing or windshield is very likely to cause stability issues at high speed unless installed and mounted 100% perfectly square, which is likely never going to happen. You are likely to have more issue with a handlebar mounted fairing or windshield than a frame mounted one as well.

[scoot]

Thank you all. I put together a small check list:

• remove windscreen
• lower rear shocks settings to mid- level
• check swing arm bearings
• check swing arm centering
• vary tire pressures
• check tracking
• measure steering head vs. frame angle

I'll run them one at a time, starting with fairing removal. Then shock adjustment, followed by tire pressures. Tomorrow. Short workday, so I'll have time to run the freeway. I carry an air pump, and shock spanner so it should go pretty good.
How's this for a tracking test?... I snap a chalk line 20' thru the garage and cover the first 10' w/ clear packing tape. then walk the bike slowly down the chalk line and see where the chalk prints the rear tire (hopefully the center). Clmer's, p.221 explains how to measure the centering of the swing arm in the frame and how to adjust it. I'll do that before the chalk walk.
natemoen, thanks for the heads- up about that useless zerk.
motoman, I do try to slow down, at least mostly.
cywelchjr, fairing is definitely not squared 100%. It's tough to line it up with anything, where do they hide the straight lines?

[Ken Talbot]

Thank you all. I put together a small check list:

• remove windscreen
• lower rear shocks settings to mid- level
• check swing arm bearings
• check swing arm centering
• vary tire pressures
• check tracking
• measure steering head vs. frame angle

Just for the fun of it, have a run through the steering head adjustment procedure if you haven't already done it, or if you don't know for sure when it was last done properly.

[scoot]

Ken, yes, I had that same idea tonite when I removed the windscreen. I have the bike on the center stand, and I scooted far back in the saddle to lift the front tire so I could swing the bars to the stops, and while I was making "vroom- vroom" noises, I was thinking to check the head nut.
I'm adding that to my to-do list.

scoot

[scoot]

Well, I just ran the freeway with the fairing removed. Tires were a little low, so I set them to 38psi front and rear. Ran like it was on a rail, and more nimble, all the way up to 115, 117mph with more speed available if I wanted it. I didn't want it. Jeez, I had to pretty much lay on the gas tank to keep my head on my shoulders.

I'll play around with the fairing position to get it as balanced and smooth as I can and call it good. Maybe look for a smaller unit that still blocks the wind pressure. I do enjoy a windshield for all day riding. And my maintenance schedule now includes checking and packing the swing arm bearings.

Thank you all for your input, I very much appreciate it.

scoot