High speed wobble??

As someone who is currently sporting a motorhead shirt I will say with confidence that if my XS makes up to Muskoka I'm all in.
 
Guys,if we could put a ride together for vintage 650,s in Muskoka,i will definately host and supply the brews,personally know the owner of the Muskoka Brewery . Did not realize there were many xs650 enthusiasts in Ont.This is my second 650 had a 1980 G SPECIAL 11 which was basically a special but with the spoked rims,strait seat 16" rear tire ect.Never should have sold that bike,it was all original including the exhausts,i do like my 77 better though.
 
Guys,if we could put a ride together for vintage 650,s in Muskoka,i will definately host and supply the brews,personally know the owner of the Muskoka Brewery . Did not realize there were many xs650 enthusiasts in Ont.This is my second 650 had a 1980 G SPECIAL 11 which was basically a special but with the spoked rims,strait seat 16" rear tire ect.Never should have sold that bike,it was all original including the exhausts,i do like my 77 better though.

Sorry for hijacking your thread, but you are my new best friend! :cheers:
I think this destination ride idea has some real potential. Shall we start a new thread in the lounge area?

end hijack
 
Hi Guys sorry I am late on this thread but just a thought on the original question. I notice the tires have a center groove on the tread that is perpendicular to the road. I have had issues with speed wobble before just because of a tire with a perpendicular groove. I got new tires and the bike was a different bike altogether. Felt so much more stable. Just my two cents. Good luck, however I would be interested to know if the fork brace had an effect, I am thinking about using one on my build.
 
once the roads r dry and snow and salt gone will try more air pressure in front tire plus check spokes and wheel trueness and alignment ,if still wobbles then i am getting the fork brace!! The way the weathers going shouldent be more than a few more weeks hopefully but i live in Muskoka and having a foot off snow drop in early April is always possible.
 
I've always used the Cheng Shin C906 front tire. It worked well and was compatible with any rear I'd mated it with .....

Front_Tire.jpg
The Cheng Shin C906 was a faithful reproduction of the Metzeler ME33 Laser. It's a good tire. I have one on the front of mine now, and a 907 on the rear. It's entirely possible to get a bum tire. I have a Conti-Motion on the front of my SV right now that is not round. I have worn out 2 sets of these tires on it, and I know they are good, but certain parts of fabricating even a modern radial are done in ways that total control is not possible.

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D, a fork brace will reduce flex in the corners, but it won't cure an oscillation; resist the temptation to throw money at the problem in hope of a fix. You're on the right course in checking inflation and trueness of the rim first. Just work the steps; that gremlin can hide but it can't run, and it'll run out of hidey holes sooner or later.
 
Well,weather is finally co-operating!! At least here in Muskoka Ont.Raised air pressure in my bridgestone spitfires to 32/36 as per post,cheaked alignment,perfect.Cheaked front fork fall away,light nudge and forks swing away,same on both sides,need to go maybe 1/2 " to get them to fall.Think thats ok.Tightened handlebar rubber mounts,were slightly loose.
Reset new rear springs to "lightest" setting for my 150lbs.Had on middle setting before.Checked all spokes and wheels for runnout,all good.Problem ,at 140k (approx 80 mph) i get a speed wobble and have to back off,up to 140 everything is perfect.What am i missing,wery frustating,tires only have approx 500 miles,almost everything on bike is new,gears,chain,rims,tires, handlebars,rubber mounts,all bushings,and bearings(steering)brakes ect ect.
 
Forgot to mention,new front fork tubes,10 weight oil and original springs shim preloaded for better ride.all new seals also,new mikes double disc and new calipers and pads also,new pads only in rear brake but all new hardware,rods,springs ect.
 
Perhaps clutching at straws but do you KNOW it is a no accident bike? Perhaps do some eyeballing/measuring of alignment of both front and rear wheels to centerline. Is the reinforcement/brace still in the front fender? How were the wheels and tires balanced?
It would be great if there were someone local that could swap a wheel tire with you for an experiment.
 
I'm going to double-ditto with gggGary here. Once ALL the normal service checks are done, and they check OK, it's time to look outside the box. Two items come to mind.

Front end - Looking at your pics in the earlier posts, little voice in my head sez: The trail looks a little short. Maybe the lower triple is bent back a little. We've had a couple threads here already on suspect crash parts finding their way back into the parts stream. Do you know how to measure your trail length? (The trail measurement on the pavement, not the derived 'true' trail.) Just FYI, we've found that trail lengths (on '70s era street bikes) that were less than 3 3/4" were very prone to hi-speed wobbles.

Rear swingarm - Not only do the swingarm bushings keep the rear wheel centrally aligned with the frame, the swingarm has to provide sufficient rigidity to resist torque/flex of the reacting rear wheel. That is, keep the rear wheel vertically aligned with the frame. A test for this is similar to the front wheel bearings and ball joint tests done on your car. With the bike on the centerstand, and a couple burly lumberjacks holding the bike steady, grasp the rear wheel at top and bottom, and try to torque it for all its worth. Look for any movement. Look for any cracks. Not just in the swingarm, but in the frame area around the swingarm mounts.

Man, I HATE hi-speed wobbles. There's other tests, but they are done at speed, and are very dangerous. I'm not comfortable with publishing them here...
 
Hi 'D,
what they all said. And check the head race setting.
Too loose or too tight can cause steering wobble.
Set the bike with it's front tire just off the ground.
Adjust the headraces so the bars stay straight until you just nudge the grip then they fall to one side.
If they flop over without the nudge the races are too loose.
If they don't flop after the nudge, they are too tight.

+1 on this. Was the source of the wobble I had on my '79. Adjusted the headset torque slightly, and it disappeared.
 
Quick question,decided to try adjusting the steering head bearing a lil tighter and test.Have never done this before,so looked it up and have a question,after loosening the main steering head nut,the pinch bolt/nut for the steering head and the upper fork pinch bolts,it states to loosen the top nut (6 stem nut)then tighten the bottom nut until u get approx 1" fall away,then tighten everthing back to spec.Question is after tightening the bottom stem nut do i retighten the top stem nut (after loosening it) or just leave it and retighten the head nut and pinch bolts. Oyeah is the upper fork pinch bolt torque the same as the pinch bolt under the head nut.thx
 
Yes you retighten the top nut while holding the bottom nut from turning, and yes two spanners are best for doing this. Recheck fall off, tightening the top nut can increase preload a bit.
 
Hi 'D,
the two notched nuts lock together to keep the bearing tension set.
You can knock them loose and re-tighten them using a punch and a hammer but it works far better using two peg-wrenches.
Break the top nut loose, adjust the bottom nut to adjust the setting, hold the bottom nut still and tighten the top nut down on to it.
 
Thx,Upon closer inspection i only had about 1/4" fall away,so now with 1" will test tomorrow and see.Still dialing in my jetting also but gettin close.Luv this old bike,its a keeper,can,t explain it,have had other newer bikes (08 Sportster 1200 Custom) but prefer the XS.I guess we all have had many bikes bu theres something about these old Yam 650,s i cant explain it.When i figure it out i will let u know!!
 
Another thought is to check your front wheel bearings. Get the front wheel off the ground, push and pull on the wheel, one hand on top of tire and other on the bottom lateral to the bike and make sure you don't have a lot of bearing slop when doing so.

Make sure someone or something is preventing you collapsing the centerstand. One option is to strap the centerstand to the rear wheel then the stand won't collapse.
 
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