What would make the front suspension on a '77 Suzuki GS550 bounce up and down?

Question

It starts to get noticable at about 20 mph, and gets worse with speed. The front suspension has a visible bounce to it, like the front wheel is going over a washboard. I checked for a flat spot in the tire, since the bike has been sitting for a while, but it looks fine. What's the likely cause of this bounce? Could this be as simple as an unbalanced tire?

Answer 1

If it was just out of balance you it would start shaking at a little higher speed. I would replace the tire. If you haven't had a tire blow out on you before you don't want to experience it. Good tires are critical on a motorcycle.

Answer 2

It is very possible that you have a wheel that is unbalanced.  All wheels need to be balanced and with bikes they normally do this by a weight around one or more of the spokes.  Look carefully at the wheel and see if you have a weight there or if there is a place where one may have come off.. Or have you replaced the tire recently.. it may be installed incorrectly.. They have a balance spot that is shown in the following Dunlop site.

Very dangerous to ride in this condition as I'm sure you have found.

See this Dunlop Tire site for more info  http://www.dunlopmotorcycle.com/infocent...

Answer 3

It sounds like your suspension needs to be sorted out. First things to check are wheel balance, Check the tyre closely and make sure it is mounted on the rim properly, if those are ok, then check and make sure the correct amount of oil is in the forks. Most people never change the oil in the forks. If you dismantle the forks, a good idea is to replace the springs with something like Progressive springs, and put cartridge emulators into them. Do it properly, and it will transform the front end. it'll work better than a new bike

Answer 4

replace the tires on the bike if it has been sitting for long regardless of how good they look.

Edit:

I would consider over a season (1 year or more) without being ridden or moved. The tires may look fine but can be dry rotted and can blow out at speed causing you serious harm. If you raise the front tire off the ground you would probably notice it is wider in the area that it rested on for a season (flat spot) This can be located by turning the wheel/tire and putting something as simple as a glass or something close to the tire. Do this on both sides of the wheel. Note the area it seems to vary in space with chalk or a colored pencil. If the space doesn't remain the same through the whole revolution, the tire has been flat spotted and needs to be replaced. you can check the tread area like this also. If it doesn't keep the same space through the turn, the tire is out of round.

Answer 5

There are two simple solutions.  It could be either, or both.

Wheel balance.  Take the front wheel to get balanced.  Get a new tire (both) since the bike sat for so long.

Worn shocks.  At rest, do the front forks move easily?  If so, you have some repair time ahead of you.

Good luck!

Answer 6

tire bad or un balance... old tire ... get a new one