Seat vibrations

[Dennis]

I have a stock 83 heartige special
When I get up to around 50 mph
I get a vibration in the seat that can make you a** go numb
Should I look at the motor mounts or maybe the rear shocks?
Something else that I havent thought of.

 

[xsjohn]

Gearing and compression and timing and carburation modifications will cure that .........when I got mine 12 years ago I couldn't stand to ride it.....now I can cruise all day at highway speeds including the expresswat without that nuisance....no one thing will really fix it properly no mater what anyone says....xsjohn

18-29
timing retarded .168 thousands
compression 8-1
My needles

70 MPH 3800 rpm

 

[pyrocentric]

Jack the bike up and really shake that swingarm to check for play in the bushings. It'd also be worth checking(or have a shop check) the balance and runout of the wheel.

Mine stock is not bad at all at 50mph. I have a nice thick homemade seat. 100mph is terrifying though.

 

[Sundie]

the three biggest contributors to vibration are loose motor mounts, unbalanced compression, and unbalanced carbs. Check those first.

 

[Dennis]

Thanks for the ideas
I never would have thought carbs since it seems to run fine otherwise

 

[XSLeo]

The carb balance or imbalance can cause too much vibration. The engine is basiccly two engines hooked together, if the carbs are off one side runs stronger than the other. If off a bunch this shows up as vibration.
One thing I did to help vibration on mine was to remove any wheel weights and install Dyna Beads. This smoothed out the ride much more than I expected.
www.innovativebalancing.com

 

[xsjohn]

Being a trained factory Yamaha mechanic I studied this vibration issue for 12 years......it's a combination of things that resolve this issue as mentioned in my first post........and yes rephasing can reduce vibes dramatically but is quite expensive.........the things I mentioned above really cost nothing ........except maybe for the gearing..........xsjohn

 

[blue900]

Yes all of the above and what John says. Getting away from stock gearing makes the most Difference in my experience.
But they all add up! to a much much smoother running and funner riding bike for sure.
Getting them running right.
And good balanced Tires is important.
Tried my new front tire once unbalanced - and then balanced it WOW wont be trying that experiment again.

 

[xjwmx]

I have a stock as far as I know '81 Special and don't have any vibration problem at 50 mph. Certainly nothing ass numbing. So I submit the fix isn't necessarily mods, but rather getting it running right stock. I'm around 3k at 55 in 5th.

 

[gentlemanjim]

XJWMX - Same here