Author Topic: Heavy vibrations from 50mph and riding  (Read 375 times)

0 Members and 1 Guest are viewing this topic.

Offline PeWe

  • Really Old Timer ...
  • *******
  • Posts: 10,711
  • Bike almost back to the 70's 2015
Heavy vibrations from 50mph and riding
« on: April 03, 2020, 02:16:28 am »
A friend has a CB750A -77 (Japanese stickers) in mint condition but vibrates very much when he rides it.  He has tried to figure out what cause these vibrations.

Any CB750A specific that can cause heavy vibrations?

Bike vibrates a lot from around 50 mph and rising.
Problems holding the handle bar.
No specific noise at idle.
4 springs inside engine and converter replaced too. Same vibrations.

Experiences with solutions/ workarounds are welcome :)

Offline sammon287

  • Full Member
  • *
  • Posts: 64
Re: Heavy vibrations from 50mph and riding
« Reply #1 on: April 03, 2020, 11:24:42 am »
Wheel and tire balance, probably the front, seems like the obvious answer. Did it lose one or more balance weights? Does coasting make a difference?
1976 CB750A

Online flatlander

  • Master
  • *****
  • Posts: 2,346
Re: Heavy vibrations from 50mph and riding
« Reply #2 on: April 03, 2020, 11:49:07 am »
i was also thinking it might be a tyre. could be that it was installed unevenly. usually if you deflate it, roll it around a bit and then inflate it again, it will seat properly.
i'd try this first as it would be the easiest cause to find and fix.

Offline Stev-o

  • Ain't no
  • Really Old Timer ...
  • *******
  • Posts: 30,549
  • Central Texas
Re: Heavy vibrations from 50mph and riding
« Reply #3 on: April 03, 2020, 12:23:02 pm »
i was also thinking it might be a tyre.

+1.  I bought a bike with an old front tire and it nearly bounced off the ground with that old, hardened tire on there.
New tire solved that issue.
'74 "Big Bang" Honda 750K [836].....'71 Honda 750K project.....'76 Honda 550F.....K3 Park Racer.....K5 Fiddy Dolla Special!......and a Bomber!............plus plus plus.........

Offline raymond10078

  • Moderator
  • Expert
  • *****
  • Posts: 775
  • Just learnin' as I go . . . .
Re: Heavy vibrations from 50mph and riding
« Reply #4 on: April 03, 2020, 12:27:20 pm »
With the bike on the centerstand - first in neutral - does the engine cause the vibration?  In gear - does the vibration appear now?  think wheel/tire balance and/or truing issues.  still nothing?  think front tire wheel issues.  weight the back end until the front wheel comes up - give it a spin, look for problems.
1978 CB750A (upgrading very, very slowly)

Past bikes - Honda: SL350, CX650C, CB900C, CB1000C, CM450A; Kawasaki: several 1972 750 H2's; Suzuki: TC90J.

Bikes I want: CX650ED, a mid-sized japanese V-twin with ABS.

Offline PeWe

  • Really Old Timer ...
  • *******
  • Posts: 10,711
  • Bike almost back to the 70's 2015
Re: Heavy vibrations from 50mph and riding
« Reply #5 on: April 04, 2020, 08:33:39 am »
Thanks guys for all things to verify.
Any specific that can happen Automatics?