free website stats program Ultra front end wobble at high speed | Harley Davidson Forums

Ultra front end wobble at high speed

D

doug rooney

Member
HI all,
Posting this for a friend with a 99 Ultra Classic. Front end starts to wobble at speeds of near 85-90 mph. I know, he's not sposed to go that fast but sometimes he does. Also was acting up the same way at about 70 on turns. Ever seen those films on high speed tracks when just before the bike wrecks the front end goes violently back and forth? That's what it is trying to do. Had it in the shop today and they tightened down the main fork nut. I followed him home and it was better in the turns but when he cranked it up, he almost lost it....Scared the heck out of him AND ME! Called the shop and they said they would re-seat the fork bearing??? We both tend to think it must be something in the front wheel...out of balance or spokes not true??
Tire was mounted by the same shop and the owner swears it is in balance.
Anyone ever have this sort of thing happen and if so, what is causing it?? Thanks for any input. Don't want to watch my best bud bite the dust! Doug
 
Has your friend ever changed his fork oil - or is one fork have a very slight leak - if one fork is low or the oil worn out it could cause an imbalance in front end - had this problem on a metric years ago.
 
My guess would be Front to rear wheel alignment or it's "True Track" time.
I love my True-Track.True-Track Home

There was a bunch posted about this a few months back.
 
Thanks guys. I don't know if he's ever changed the fork oil but he's pretty dilligent about maintenance. The bike is near spotless and he certainly would have noticed a leak. Wheel alignment....interesting. Could very well be.
I've sent him the link to the HD forum so will ask him to join. It's free and cuts out the middleman (me) who doesn't know all that he does about the bike. Appreciate the replies. Keep em comin'. Doug
 
I'm not going to pretend to be an expert on these bikes (yet), but from my race bike days, what you are referring to is called a "tank slapper." Might want to check the play in the steering head. It is part of the regular interval checks and the procedure is spelled out in the manual.
 
Also have him check the steering bearings for lube (if you need a whole cartridge at the zerk fitting, it was dry) then for play by applying the front brake and really jounce the front end feeling the bar and looking for "clicking" and "crunching" sound of rusty/worn bearings. Put the bike on a jack and check for fall away and check for free movement, again pressing fork at diffent positions for tell tale "click" or movement. Then of course you should drain the fluid, (check condition and amount of fluid in each to see if proper level was maintained, and no excessive debris). Finally, rotate the tires and look for runout in the linear and concentric directions; then the tread pattern for "normal" wear without cupping or evidence of odd wear pattern with the palm of your hand to feel for variations. Certainly a lot to check before getting to the disassembly and inspection phase.
 
GREAT! You guys know your stuff as I figured you would. Tank slapper huh? It's certainly trying to do that. Just don't want him to be a pavement slapper at 90 per!
Sending him an email to sign up and answer for himself so if I don't reply further, it's because we're waiting for him to show up. He'll see all this so anymore info I'm sure he will greatly appreciate! Thanks, Doug
 
A few months ago I ran into a problem somewhat similar.

If the bike has spokes, check to see if they are loose. I developed a drift in the bike that at first we couldn't explain, checked everything that was recommended by others but found out I had spokes loose, so loose I had to replace rims, No mores spokes, wont have that problem again.

I guess more maintenance and less riding would be a good rule for me to follow?
 
JDPEagle said:
I'm not going to pretend to be an expert on these bikes (yet), but from my race bike days, what you are referring to is called a "tank slapper." Might want to check the play in the steering head. It is part of the regular interval checks and the procedure is spelled out in the manual.
Click to expand...

I agree with JDPEagle. this is a very dangerous condition and needs to be addressed. The fall away adjustment in the service manual should tell you if the bearings need adjusted.
 
jaceddie said:
I agree with JDPEagle. this is a very dangerous condition and needs to be addressed. The fall away adjustment in the service manual should tell you if the bearings need adjusted.
Click to expand...
I think Harley did the gambit on this problem, in 02 they changed the front fork config. on the Faring models, hopeing it would get rid of the wobbel, it didn't. The problem seems to show up mainly in the Batwing Faring bikes and is always unexpected and sudden. My buddy had it happen on his 99 FLCH on a bridge, even after he got his bike stopped the shakin didn't go away for him for a hour or 2. Anyway the realy smart guys, now, seem to think the wobble starts in the back of the bike, road grooves, uneven tread wear, even belt misalignment. And works it's way up to the front, when it hits the neck, it just goes crazy. Most people find that breaking causes it to get worse cuz it loads the front end. Anyway, my buddy installed one of the first "Tracking" devices that came out and his bike ain't wobbeled since. The device mounts under the tranny and uses the crosspiece under the frame to stiffin the rear mount of the motor. It's suppose to stop the transfer of the wobble through the frame.
Good luck, hope ya find a solution and let us know what happens.
 
You must log in or register to reply here.
Back
Top