Topic: Front end shimmy @ 40 MPH

[benny365]

My front end shimmys at 40 mph mainly when decelerating.  Possibly steering stem bearings or forks going bad?.
I replaced the tire, not that. (It needed it anyways)

What do you think?

73' 750

[Dave K]

My '73 K3 would do that also if the front tire was worn or the wrong tread pattern on the front tire was used. (my '81 Goldwing would also) I am sure you checked the usual other things like swingarm bushings, head bearings and wheel bearings also.Check your front fork fluid as well and make sure the front fork springs are sagged to much. This will change the front end geometry and decrease your rake and trail, possibly creating this condition. Unfortunately, this is not an uncommon happening with model. All it takes is one finger on the bars to prevent it also.

[Pinhead]

As mentioned, check (change) front fork oil. You may possibly need to change your rear shocks as well. My 650 does that slightly if I try to carry something heavy on the back (behind the back tire on the luggage rack). The extra ballast throws the gemotry of the bike off and causes the front-end to wobble.

[DammitDan]

Check your spoke tension on the rear.  I had loose spokes that made it shake pretty badly, especially on decel.  Then I realized that I was constantly 2 seconds away from death and tightened them correctly 

(then I got rid of spokes completely and went to mags!)

[mikes]

I believe all the 750s suffered from that problem. Try puting just one hand very lightly on the throttle at about 40mph and roll off quickly while leaving your left hand off the bars, it will shake a bit. Best remedy for that is a steering damper. They tend to stiffen up a loose condition with a mild fork angle on a heavy bike. When i raced on dirt tracks i would get a severe shimmy or wooble at high speed on a very light bike, espically on a mile dirt track, and the dampers helped a lot to correct that condition. We called it the shakes. If i complained about it, they would tell me to run it till it melts!

[BobbyR]

That can be a worn bearing, they call it a decell wobble. You said you changed tires. i had the same condition when I changed tires. i found the newer type tires have softer sidewalls so the recommended pressure was no long valid. I raised the pressures and it wne away. Try the easy way first is my motto.   

[Mark M]

How bad is it - do you notice it with your hands on the bars or is this only noticed with hands off?
ALL bikes will do this to some extent at aprox 35 mph, it's caused by the trail. The road deflects the
steering and the trail straigtens it.
If you are feeling it with your hands still on the bars then you need to check the simple stuff first.
1) tyres and airpreasure.
2) wear and tear to bearings, start witht eh front wheel, steering head, rear wheel and swingarm pivot.
3) are the wheels running true, any rim/tyre damage etc
4)suspension, probably less likly as this will be evident at other times than just deceleration at 40.