ST1100 Front end bounce

[z400d3]

I bought a 1998 ST1100 back in 2018, it had been laid up for a few years but after a bit of tidying up, including new fork seals, it was running well, I have done over a thousand miles on the bike since putting it on the road with no handling issues, the agility surprised me for such a heavy bike

I was out riding with some friends last summer, we'd done about 60 miles and pulled over to say goodbye as we'd be going off in different directions.

I rode off on my 12 mile journey home, had gone about a mile or so when I noticed the front end didn't seem right as I approached 40mph

The best way to describe the symptoms is to say that it feels like the road has millions of small ripples in it causing the front end to shake constantly, makes it feel like you filings are going to fall out

The symptoms start at 45mph and get much worse as you approach 50mph, I have tried getting up to 60 to see if you power out of it and it does feel like you do, you certainly feel it as you come back down to 50mph, but as you can imagine I'm not to keen on doing that sort of speed for long with this sort of symptom

Below 40mph the bike feels prefect, you'd never know there was anything wrong with it

I have changed the front wheel and tyre, changed the forks, fitted tapered head race bearings and checked the frame etc for an obvious signs of cracking etc but the symptoms persists

I have searched through the forums etc but can't find anything that resembles this issue, I did find a few posts suggesting that headrace bearings could cause an issue which is why I changed mine as a precaution

This is driving me nuts and would appreciate any input


Cheers ... Chris

 

[TerryS]

The fact that it is speed sensitive suggests to me that an out of balance wheel might be the culprit. These are undetectable at low speed and usually reach their worst at 50-60mph before fading away again. Maybe also check your tyre for roundness, if it was parked up for a bit you may have a flatspot on the tyre. It is also not impossible for a tyre to internally delaminate which can also cause the shudders. So my suggestion, take the wheel to a friendly bike shop and have them check the balance and they can also look at any out-of-round or run-out issues while it is on the balancer. If it persists I'd be fitting a new tyre.

 

[Uncle Phil]

Most of the weight is in the rim not the tyre.
I'd balance the rim first and see if that helps.
Also, what pressure are you running in the front?
Too much can make it really ride hard.

 

[SMSW]

I'm with @TerryS - an out of balance front wheel. As far as balancing the rim alone, if you balance the assembly now, that will take care of any balancing needs for the rim. Every new tire I've ever bought was balanced on the rim - car, bike, truck, and a fully balanced rim does not remove the need to balance the assembled wheel. I prefer spin, but careful static balancing is also good.

If that does not solve your problem, I'm sure @Igofar would suggest loosening the axle bolts and following the procedure to reinstall the wheel. Also, check the fork triple clamps for proper torque.

 

[red one]

Might be you need a suspension check. If you have a lot of miles. Forks springs and fluids and rear shocks are toast after about 80K according to some here. At 81K I probably need to check mine.

 

[sirbike]

Being all of a sudden, sounds like you threw a weight. What type weight? Stick on can slide off. The Honda center line weight is the best weight.
Ride on balancer/sealant is my choice.

 

[Slydynbye]

Maybe time to check the new steering bearings. They need sometimes need to be re-torqued after some bedding in. You could check by raising the front end off the ground and looking for play in the steering yoke.

 

[dwalby]

your symptoms sound exactly like the dreaded ST1100 headshake.

It tends to get worse as the tire wears, so that's one possibility, but that wouldn't seem to come on all at once. An out of balance tire might also be the culprit, I don't have any experience with that. I agree with slydynbye, I'd guess the bearings could be the most likely cause if you've changed them and never re-torqued them.

 

[kiltman]

My experience with tapered bearings torqued to OEM standard bearing specs results in a low speed wallow, really present at 5-10mph. Retorqueing them by feel, produced the best results, no head shake whatsoever.
my experience on worn steering head bearings or bearings not not torqued enough leads to vibration of the bars at 35-60 mph and the tendency to wobble. At speeds from 25mph and up, if I lifted my hand off the bar or loosen my grip I could visually see the bar vibrate up and down, side to side by a few millimeters.
I’m a plus 1 on checking the torque on the head bearings

 

[dwalby]

Retorqueing them by feel, produced the best results, no head shake whatsoever.

agree with this, that was what I found to work best eons ago when I did mine.

What worked for me was adjusting them until they were obviously too tight, then backing off a little until the tightness went away. Any looser than that and I still had the wobble around 40mph.

 

[kiltman]

As an aside, I believe that after the first 1000 miles of operation(when the bike was delivered new or when the steering head bearings are replaced) Honda recommends that the bearings be checked and retorqued if necessary. As it’s a labour intensive service I think many owners and dealers opted to not do that on the first service interval. My observation, around the 60,000 mile mark a lot of the ST’s would have a wobble issue and was always noticed when new tires were installed. The consensus being that tires were the issue when in fact the steering head bearings were the issue. If however the recommended checking and retorquing was done the bearings lasted considerably longer before needing replacement.

 

[ChriSTian_64]

Being all of a sudden, sounds like you threw a weight.

+1

 

[John OoSTerhuis]

Guys… he changed the front wheel, tire, forks, and steering bearings and still has the symptoms! It doesn’t appear that he edited his original post to add what was replaced.

John

 

[dwalby]

FWIW, until I got my tapered bearings adjusted EXACTLY right, I still had headshake, so new bearings by themselves don't rule out that possibility.

 

[kiltman]

Is it possible one of the front brake rotors is warped?