Motorcycle Repair: Honda Shadow Spirit 2005

Question
My Honda Shadow Spirit 2005 "dribbled" I dont know how to explain te problem. All the bike "up and down" especially around 40 and 60 miles/hr. The only term that I think is "dribbled".
After 6h of verification, verdict: she's old... I'm not happy with this. Does anyone had this problem?
Verification done:
Front and rear tires and rims, all engine screws. Oil and seal changed on front fork. "Bushing" on rear suspension replaced. Even Honda Canada dont know what's the problem...

Answer
Hello Sylvie,

When you say "Front and rear tires and rims", what do you mean? Checked, replaced or balanced ?

Are the wheel spokes tightened and perfectly balanced ?
Did you, by any chance, put any kind of flat-tire-preventing liquid material in the tires ?
Have you had a flat tire and fixed it with some kind of quick repair ?
If yes or not sure, visit a tire shop, and have the inner tubes replaced and the wheels balanced again.

Get back to me with answers to the above, and more details on what exactly has been checked.
I'll be more than happy to further assist you on troubleshooting.

Best Regards,
Lazaros.