Kz650 Wobble

My kz650 has had a wobble since the day I first rode her. Symptoms occur upon initial acceleration (wobble in one direction) and taking turns at higher speeds (40-50mph) I have changed fork oil/air pressure, balanced tires, aligned wheels, checked for play in the wheels (wheel bearings), and turning is smooth (steering stem bearings). At this point Im not sure what else to check. any input is greatly appreciated as this has been a recurring and unfixed problem.

thanks for you time and input.

-Nick

just a shot
your not choking the handlebars to death are you? (grip)

NickMac wrote: My kz650 has had a wobble since the day I first rode her. Symptoms occur upon initial acceleration (wobble in one direction) and taking turns at higher speeds (40-50mph) I have changed fork oil/air pressure, balanced tires, aligned wheels, checked for play in the wheels (wheel bearings), and turning is smooth (steering stem bearings). At this point Im not sure what else to check. any input is greatly appreciated as this has been a recurring and unfixed problem.

thanks for you time and input.

-Nick

KZ650 bikes should have ZERO wobble from 0 - 120 mph. If there's wobble, here are the likely suspects:

Tires - these can look great but cause wobble. I had Michelin Macadams do this to me, and it had nothing to do with tire balance - they were perfectly balanced. If your tires are not new I would replace them and see if wobble goes away. Fixing everything else below can help mask a tire problem but will not completely eliminate the wobble if the tire is at fault.

Rear shocks - toss originals, get QUALITY shocks (I use Hagons.)

Swingarm bushings (or in later models bearings). Raise rear wheel, disconnect shocks, try to twist tire left/right, check for any play at all. There should be NONE. Replace bushings / bearings if in doubt.

Steering stem bearings - replace originals with tapered roller bearings and be done with that possibility.

Fork oil - purge old oil - fill to the CORRECT level with quality fork oil (I use 15w Bel Ray).

Wheel bearings - repack them or better yet replace them (especially if they don't feel dead smooth).

Wheel alignment - front and rear tires must run parallel.

Wheels - if your wheels have spokes check the wheels with dial indicator to make sure they run true.

Brakes - make sure disks aren't warped and contacting pads irregularly.

If all the above are done and wobble persists you make have bent forks or frame. Ed

You haven't mentioned your swing arm.

I don't know what year you have but the first ones didn't have roller bearings they use a bushing.

Ether way if it wasn't greased regularly they will wear out and cause slop .

How many miles on her and how long have you owned it ?

What does your chain and sprocket look like ?

JD

Ed beat me :pinch:

Im sure everyone who reads this will roll their eyes... The bike is hardtailed via the swing arm. this is the reason I have not mentioned the swing arms bushing/bearings or the rear suspension.

The front end is off a kz550. Today I checked everything and wanted to take the bike around the corner to see if the anything I had done had affected the wobble. As soon as i got on the bike I notice the forks where not properly dampening. oil is 10w bel ray and air pressure was set to factory specs. i just changed to seals two weeks ago and no oil is leaking and the air pressure hadnt changed. any ideas? hopefully its not the spring.

Considering the bike's suspension has been seriously modified the problem may be inherent to the changes. Who knows how much care and science went into the hardtail, but in any event, a hardtail bike will not handle as well as a bike with a rear suspension. I would not recommend anyone with a hardtailed bike try taking turns at speed as there is no provision to keep the rear tire in contact with the pavement if there are even minor bumps in the road surface. Ride slow. Ed

NickMac wrote: hardtailed

There's your problem.