T120 Low Speed Handlebar Oscillation

Hi,
I have A T120 model 2017, total milage currently 8000.
After about 5000 miles I have experienced handlebar oscillation.
With loose hands only at about 40 MPH. So bad that I would crash if not grabbing the handle bar.
(I know I shouldn't drive with loose hands.)
I read in other conversations that the cause would be the worn tires.
So I replaced them allthough there still was enough profile with pirelli scorpion trail 2. (very nice tires)
The oscillation was gone .. almost but not entirely. Now I can drive with loose hands but there is still oscilation,
not dangerous anymore, but annoying.
My dealer (not a triumph dealer) already checked bearings etc and could not find anything.
I have replaced the fork springs by TEC forkspings and the shocks by YSS topline.
Also placed a fork-brace from britisch customes.
All feeling very well, the bike has become al lot more agile while cornering in the mountains.
Does anyone have tips for me?
Should I make the bike original and claim warrantee at Triumph or is this normal behavior?
Thanks,
Bert

 

Yes, the original ones from Triumph. But also with no bags on it, it happens.

 

I have a givi rack at the back, but there is nothing on it. I have chosen it because the original Triumph one is specified for only 3kg.
I put a topcase on it if i go on travelling. I suppose this cannot be a cause with nothing on it. Could it?
Anyway i need it when i have lugage.

 

The YSS do have a setting screw to make the shock longer. But i have kept them on the minimum length
So they should be the same as the stock length. Do you think I should try putting back the original ones?

 

Today i did more tests and also replaced the YSS chocks by the original ones.
The oscillation occurs between 70 and 80 km/h.
A lot of roads here have 80km/h speed limit, so i am often at this speed.
The original shocks and the YSS are of the same length.
The YSS springs are a lot softer, I can press them in about 10 millimetres by hand. The original shocks I can not press in at all.
To make a long story short, with the original shocks I still get the oscillation.

 

Tires are quite new. So balance must be good. I have no equipment to test this.
Before the new tires the oscillation was so bad that I would crash.
With the new tires it is only annoying.
Rack is still on.
Could you elaborate more on why you think it could be rack related?
I mean a few tubes of metal not much weight,
Is hardly to believe that this has influence.

 

Yes its work and anyway i need it for my holiday soon. I will try to make time next week. I have my own business and it's very busy at the moment.

 

If have now the Pirelli Scorpion Trail 2, yes there are triangles.
I asume the motor shop does the balancing and mounting right.
I told them about my problem, so they should be extra carefully, they also checked the bearings.
I have no tools to check the wheel balance.
With the original tires, the shaking was a lot worse.
For me the tension of the tires is unclear though. I hade these als on my triumph tiger, where the tension was 2.5 / 2.9 Bar.
The bonneville manual says 2.2 / 2.5 Bar.
Would this make any difference?

I will remove the rack next week and let you know. But how could the rack have influence, any idea?

 

Yes I had this tire on nu tiger and i liked it. Never slipped in the rain.
With the original triumph tire my rear wheel has slipped several times make me feeling unsafe in the wet.
On the tiger I got 10000 miles with these. Also in other forums these tires where recommended.

 

Today i tried with the givi rack off.
No difference at all.
Set Tire pressure to 2.2 / 2.5 bar. No difference.
Shocks original triumph.
Tried various preloads on the shocks no difference.

 

Thanks for the advice. Will go back to my dealer. I will Let you know.

 

Sorry i am dutch, what are races?