Since I know nothing about "stability issues", I'd start with steering neck bearing adjustment and lubrication, then move on to wheel bearings, then move onto swingarm bearings. Then maybe remove some weight that is high up on the chassis, then consider tire flexion, then the engine rubber mounts. Well, maybe before all this I would look at the handlebar width and rider training. This, I nothing about...

 

Animal

Head bearings / wheel bearings / motor mounts / rear wheel alignment (which could go back to the mounts) is where I'd focus

Once those are verified - suspension - tire balance

Scoot should run solid well over 80 - something is obviously breaking down

fwiw - dyna section - we get off on wrenching / diagnosing / modifying **** - feel free to drop in


Ghost

 

I assume you are referring to head shake and not the death wobble video recently posted? Head shake will intensify to a tank slapper if not controlled.
My '09 Road King did this. Dealer could not fix and just warned me not to let go of the handlebars. FWIW, my FXDC is stable at 80 and beyond.

 

Maybe take a step back and start simple. Take the shield completely off and take her for a spin, at 80. Maybe the mod you did is a contributing factor? And as others mention, these bikes can handle 80 with no problems. I'm just back from my Sunday morning ride...shieldless and 80+ for a small stretch of highway with not the slightest of a wobble or shake.

If not, see Ghost's response.

Good luck and let us know what you find.

Good post. You may be correct in that it's a wrong description on the OPs description. I had that on my old metric cruiser and it was miserable over 65/70.

 

Check for a "cupped" or badly worn front tire.

 

That's what the tech suggested when I talked to him over the phone yesterday,I did cut the windshield about an inch or so by speedy auto glass,so it was a professional that did it not by me,lol.It is adjustable on the forks,I did this for this reason,in case I screwed it up I can always put the windshield up on the forks back to where it was before I did the mod,just haven't been able to take it out yet,other things need to done around the house first,appointment at dealer is scheduled for Tuesday morning,weather permitting.

 

Well cool man. Safe travels and let us know how it turns out.

 

Finally was able to take the bike out yesterday without the windshield and I also checked the handlebar bolts,they were tight,still same result,not very nice riding without a windshield at high speeds,anyways,it's raining here today was supposed to get in for service but now it's been pushed back to Wednesday afternoon,I'll let you know how things go.

 

Sheesh man that doesn't sound good. Let us know...

And FYI - seems my FXDL loves it when I leave the shield off. I mainly cruise back roads though.

Safe travels.

 

If it's a slow wobble in the front end, check the steering head bearings and that your steering head is adjusted correctly. Could be wheel bearings too. You're front tire will wear unevenly (in a scalloped kind of pattern) if it's your wheel bearings.

Only other thing I can think of is to check the motor mounts. Does the bike have any aftermarket stabilizers installed (True-Track)? Make sure everything is bolted snug down there. Do you have laced wheels? Make sure those spokes are tuned and not loose.

Curious to hear what you find out.