Front wobble at speed in curves only


XS650 Addict
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San Diego, CA
Hi all,

I know there are some threads on front end wobbles, but it can't hurt to ask again.

My bike tracks straight with hands off the bars and does not wobble (as much as I can tell) at speed (~80mph) in a straight line. However, if I'm heading through a long curve at speed (50+ mph) and hit any kind of road irregularity the front end starts oscillating right to left really bad. It seems it was pretty minor and has been getting worse.

Here is what I have done:
New matching tires (avon's) front and back - same type I had before
Added balance beads to the tubes front and back
Tires inflated to 28-30 psi
7.5oz fork oil per leg
Triple tree lowered ~1/4 in on the forks
Tightened up the previously installed tapered steering bearings

Here's what I'd like to do:
Install new wheel bearings front and back
Replace the swingarm bushing/bearings (I have the needle kit from AllBalls)

Any other suggestions???
Hi tkurt,
Didja do the "just drops to one side if you nudge the bars" headrace adjustment test or didja just reef 'em up a bit?
Too tight can be as bad as too loose for a headrace.
I'm with angus, the "usual suspect" here is poor swingarm bushings.
Aided and abetted by worn rear shock dampers.
Heads up on that all balls kit some were shipped with the wrong bearings, measure the depth of the bearing bore in the swingarm compare to the length of 2 bearings and the hat bushing. there should be one long and one short bearing for each side.
Any difference left or right turns?
Push both bars to cancel a wobble. pulling makes it worse.
Did you check swing arm play with the bike on the centerstand? How much will the rear wheel move side to side?

My stock 79 wobbled with vigor at high speed, IF I induced it, the all balls kit stopped that.
Hi guys, thanks for all the feedback.
-The wobble definitely seems worse when turning and leaning to the right

-I didn't due the headrace adjustment perfectly since I was too lazy to unhook all the controls to get the wiring and stuff out of the way, so I just "reefed em up a bit". Could be too tight now I spose. Is there a quick way to know if they're too tight?

-I definitely suspect the swingarm bearings could be bad, I get a click type feeling and a bit of wobble (maybe 1/4 inch play right to left) when I push/pull on the rear wheel with the bike on the center stand

-Thanks for the heads up on the bearings gggGary, I'll check em out before install. And thanks also for the tip on how to manage the wobble, if it happens again - I'm trying to take it slow until I get the upgrades done

-Also I'm running a front fender but no fork brace.
If you want a nice upgrade and stability improvement, get a TX750 swingarm. They are pretty much identical to the 650 one but have about 1/4" larger diameter arm tubes. They use the same bushings and pivot parts so your bearing kit would fit.

Some bikes benefit from a fork brace, others not so much. The 650 does, especially because of the brake on only one side. Grab it hard and it tries to do a lot of fork twisting.
Is your front fender a stock XS650 fender? These fenders have a fork brace of sorts built right in. The steel piece that actually bolts to the forks and the fender mounts onto is made from fairly heavy steel. This acts as a brace. I wanted to replace my stock 75 fender, I got one from an XS1100. The bike handled poorly. Got to looking at my stock 75 and 81 fenders and comparing them to the XS1100 fender. The XS1100 fender mounting bracket was made from much thinner steel. Not as strong as the XS650.
I tried the 81 fender on the 75 and worked much better. I got a later XS650 fender for the 75.
I think reason the XS1100 fender had the lighter steel was that with the 37 mm forks it didn't need the extra bracing.
Something that I have been seeing a rash of lately by DIYers and shops is tires mounted incorrectly with the tires not seated on the beads. There is a molded line on the tires right next to the rim lip. This molded line should be visible and equal distance to the rim lip all the way around the tire, on both sides of the tire. If there are any spots where this molded line is not visible then the tire is not mounted fully on the bead. Remedy for this is, re-break the bead, lube the tire, inflate again. Also there is a lot of ignorance about inflating a tire to seat the bead, 60 pounds regulated pressure should be used and done quickly.

Harley owners should disregard this because Harley rim lips are mostly wider than the molded line. Someone should tell Harley why that molded line is on the tires.

Hi guys, thanks for all the feedback.
-The wobble definitely seems worse when turning and leaning to the right

-I didn't due the headrace adjustment perfectly there a quick way to know if they're too tight?
Yes ....with the bike on the stand and the front wheel off the ground, the headrace shouldn't be so tight that the handlbars and front end doesn't freely fall both sides of the straight ahead position.
A quick check to see if the headrace is too loose is to stand facing the bike with your legs either side of the front wheel and with the front brake on try to rock the bike back and forwards energetically . There should be no clonks or clicks coming from the front end.

-I definitely suspect the swingarm bearings could be bad, I get a click type feeling and a bit of wobble (maybe 1/4 inch play right to left) when I push/pull on the rear wheel with the bike on the center stand

Its difficult to apply sufficient force to the rear wheel to test the swingarm bearings adequately without the bike moving about. Any movement of the wheel /swingarm is indicative of considerable wear or mal adjustment of the swingarm bushes,axle,locknut etc

I need to check mine as the bike feels like it has a hinge in the middle when there is a head or crosswind:yikes:
It's been quite some time since I replaced bushes on the 650 swingarm. That being said, isn't there a torque applied to the swingarm bolt? Doesn't that all apply to the rigidity of the frame/swingarm assembly? What happens if we put needle bearings in there? Is the same torque still applied and does it function that way? Someone told me along the way that if I put bearings in there I would need a brace welded across the frame above the swingarm. True?

Lots of questions, I know.
The torque is applied to the pivot tube not the bearings so remains the same no matter the bearing used. Checking pivot shaft to assembled bearing face clearance, and shimming if needed is part of the assembly procedure. That brace seems like a good idea but the bolt-nut torque is designed to deflect the frame a bit to take up clearance. , get it rigid and careful shimming between frame and cups would be more important. This would be separate from the pivot shaft proud of bearing face shims. The whole XS650 swing arm pivot is hokey old crap.
Quick update -

I found that with the tightened-up stearing bearings, the handlebars and front end would fall very easily towards the right but not towards the left. I loosened it up and set it at spot where it falls more easily towards the left (its still looser towards the right).

After riding for a couple days, I think the front end feels a little looser when I hit small bumps and road irregularities but this may be normal, its just different from the feel when I had the steering column really tight. The good news is that I have not had any of the strong back-and-forth oscillations in hitting bumps on long sweepers.

I'm planning to tackle the swingarm this weekend.

Also, my fender is stock '78. So do you guys think this should be sufficient, or is it still a good idea to get a brace? If so, would this work:
I think I do not like that righty tighty lefty, loosy thing you have going on at all. My suspicion is that one race is not correctly seated. That front end should be pulled and inspected.
Agreed, sounds like the steering races need to be looked at/replaced.

Your fairing should be good, it has a built in brace...likely fixing the steering will make the bike solid again, and if you do the swing-arm, all the better.
What you linked to is not what you want and no, it won't work. That is what's called a tweak bar and is used on the upper tubes of an extended front end. You want something that clamps or mounts on the fork lowers like so .....


But as mentioned, you seem to have other things going on. Just throwing a fork brace at them probably won't help. If you want to spend some money, get the tapered bearings for the steering head.
Thanks for the additional tips and advice. I will start with the front end. I had already installed the tapered bearings but now suspect they're not seated correctly. I'll skip the brace for now.

Is it possible to damage the tapered bearings by over-tightening? Should I replace completely with a new set?
You shouldn't have damaged the bearings with your minor hand over-tightening. Possibly if you left them that way for a long time and many miles, but you didn't. If you still had all the cables and wiring looms in place when you did your testing, they may have been the cause of the one side not falling as quickly as the other. The tapered bearings are run pretty snug, tighter than the loose ball set-up. If you get them too tight, the bike will usually exhibit a gentle weave back and forth at moderate speeds, say 25 to 35 MPH. It's not a tank slapping handlebar wobble but rather a weave back and forth on how the bike tracks down the road. Almost as if you were steering a little left, then a little right, then left, etc.