Bouncy Ride 78 CB550

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So I am having trouble trying to get my CB550 to ride smoothly. I knew it was bad since it is the only motorcycle I have really ridden more then a few yards I didn't know if it was just something normal until i rode my dads nice BMW this weekend and it was very smooth.

My bike feels like it has a flat spot in the rear tire of something that creates a very bouncy ride. I have brand new tires with only 100 miles on them. I put them on my self and at first the bead would not seat and I figured that was the issue. Now I'm pretty sure I have a bead seated and it is still riding terribly. It may be possible I still need to get the bead to seat better I am going to double check it in a bit. If the wheel was out of true would it create this issue? Also what if the wheel was not aligned straight would it create this problem? I replaced the wheel bearings on the front so but I have video of the front wheel while riding and if doesn't look like thats the issue, it also feels like it coming from the rear, I can feel it in the seat not the bars.

Cycle gear balanced the wheels for me so I guess there is a chance the are not balanced correctly. Can anyone give me a starting point of some issues to work through?

 

[SONICJK]

Either the wheel isn't true, or the tire isn't balanced.
Most likely both.

 

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After spinning the wheel while on the center stand it stops at different places every time. Also looks like the wheel is true as well based on a field test of the trueness. It seems like the bead is not quite the same all the way around and is possibly my problem, it is only a very slightly difference and I have tried multiple times to get it to seat correctly.

 

[TheCoffeeGuy]

Check for loose spokes, tapping them with something lightly, they should all sound the same with no "chiming" sounds. As well check front fork oil, check rear springs.

It can be out of round, and still in balance. Check to see if it has run out on the rim.

I would also get some one else to ride the bike. Watch the bike as he gets on, what happens from the side and behind as he rides.

 

[ILoveThumpers]

Is the bounce relative to wheel speed? What I mean is, as you speed up, does the vibration get faster? Does the bumpiness change based on road surface?

Find a newly paved road and do some riding at various speeds. If it always seems the same at all speeds, it's probably not out of balance or out of round. (It could still be untrue... need to measure this, not by eye)

This would indicate a shock problem (rear or front... it sounds strange but fork issues can make the rear end feel funny and vice versa)

Lastly, what kind of BMW? Big heavy bikes like the GS series are very smooth and have very little road feel... lighter, stiffer bikes are just bumpier by nature. I'm just trying to determine if you're comparing a Lay-z-Boy with a stepstool or not.

-Deek

 

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Thanks for all the replies guys! I have a lot of stuff to check on my day off.

It does seem to get a little worse as I get up to speed, and not very noticeable at say, around 30. It may very well be my rear suspension as I'm sure they aren't working very well being so old. I will replace my fork oil on my day off and see if it helps as well. As far a the rear suspension, I could buy new shocks/springs but they would be the cheap models since I just don't have the money for nice ones right now.

The BMW I rode was a 1973 R75/5, so its not that heavy, i think around 450 lbs.

 

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I took it out for a spin today and backed the preload down a few notches, it made a world of difference. The underlying issue is still there but it is much much better and actually pleasant to ride now.