Topic: Shake/shimmy in bars at speed... Ideas?

[Dunk]

I have a '71 CB750 that gets a shake or shimmy in the bars above 35 MPH or so. I don't relaly notice it at those speeds unless I let go of the bars. Then I can watch them slowly start shaking back and forth. After a couple seconds it gets real bad and I gotta grab back on. At higher speeds (65-75) I can feel it and grip a little tighter on the bars. At particularly high speeds (120+) the wobble becomes severe and it seems no amount of gripping the tank and bars tight will prevent the inevitable. Now I don't make a habit of going much faster than that but I'd certainly still like to fix the problem. Today I put the bike on the center stand, a challenge in and of itself, and checked for anything loose. Rear wheel, swing arm, front wheel and forks all seemed tight. No wobble or feel that would seem to indicate worn bearings or bushings. So I'm confused as to what the problem could be. Any ideas?

My last bike, a '72 CB750, had a similar wobble, but it was silky smooth until about 80 and then got progressively worse. I kept my speed below 80 and didn't worry about it, but with this '71 the wobble starts at a low speed so it concerns me more. Thanks for any thoughts.

[Hush]

Think I have seen something about this problem on forums lately, came down to front wheel offset as I remember but don't quote me on that.
Some how the spokes are set slightly off centre (to allow for single disc weight I'm guessing)
It definately has to be something around the front wheel area to give you shake in the handle bars.
Plenty of experts on the 750 on here so wait a minute and they will put you right.

[750K2]

no expert here but i noticed what sounds like the same symptoms on my bike when i wanted to see how fast it would go.  i got up over 90 and the front wheel started shaking a bit.  at 105 i backed off the throttle as the shake really started getting worrisome. (ya, maybe i should have slowed down prior to that point...)   i put the bike up on the center stand and checked the front wheel for runout along the rim.  sure enough, it was out so i adjusted the spokes and trued up the front rim.  silky smooth after that.  check your rim for true in circumference and side to side.

[andy750]

Good advice from Frank (750K2) and def check the spokes. I had a similar shaky bar experience but only around 35-40mph and then smoothed out at higher speeds. Turned out to be front tire pressure was too low. I dont think this is your issue as you have it getting worse at higher speeds. Could also be rear shocks are too stiff - this does affect front handling - Ive tried it  or steering head bearings are shot. Thats all I can think of for now.

good luck and keep us updated on what you find.

cheers
Andy

[Johnie]

I agree with the guys and the truing of the wheels.  I had that problem on the Goldwing and it was gone once I packed the bearings.  I then found the steering head was also very loose.  You may want to pack your steering head bearings and check tightness if you have not done that already.  An original K2 with no steering head maintenance will need some grease and I bet the head is loose over the years from use.  My KO needed the grease and the head was loose too.

[Phxmark123]

I had the severe shake at 105mph on my KZ900....swingarm bushings, a little wear there creates a lotta shake in the handlebars.