Occasional wobble

[JPaganel]

I have this wobble that happens if I am not holding bars tight or let go one hand. This is typically apparent at lower speeds, around 35-40 Mph and lower. As soon as I put the other hand back on the grip it stops. This is intermittent and doesn't happen every time I am in that speed range. At highway speeds the bike is rock solid stable.

How abnormal is this? My front tire is kinda worn. Could it have something to do with that? What else can it be?

[Rhino]

shouldn't happen at all
my old girl is rock steady, I can coast no hands (not a recommendation) for ages until the speed drops off.

if you're up for a new tyre, get the new tyre and a good balance and see if it stops.
Maybe get the back balanced at the same time.

could be aero related, in a certain cross wind, buffetting. But this would only be if you have some non std things poking out into the airstream i would imagine

[FJmonkey]

Check again after you put a new front tire on. If you still have the issue then consider steering stem bearings, front wheel bearings. Heck, try increasing your front tire pressure to see if that makes a change, could give you a hint if the front tire is the cause. Just don't use tire pressure to fix your problem, keep the tire pressure set properly for the safest riding...

[JPaganel]

shouldn't happen at all
my old girl is rock steady, I can coast no hands (not a recommendation) for ages until the speed drops off.

That's what I figure. Might have something to do with us having lots of grooved concrete pavement around here, too. I've noticed some rubber likes to follow it more than others.

I have a new Shinko on order at a local shop (guy quoted me $2 over what it would cost shipped form an online dealer, I'd rather feed a local). We'll see what happens.

Is it worthwhile replacing the bearings while I have the wheel off, or am I better leaving well enough alone?

[FJmonkey]

Is it worthwhile replacing the bearings while I have the wheel off, or am I better leaving well enough alone?

What do you know about the bearings? Have they ever been exposed to a pressure washer? With the bike in the center-stand and enough weight on the rear seat to lift the front wheel, how does it feel when you spin it?

[JPaganel]

What do you know about the bearings?

These specific ones on this bike? Not a thing.

Have they ever been exposed to a pressure washer?

No idea.

With the bike in the center-stand and enough weight to lift the front wheel, how dies it feel when you spin it?

Dunno. Will go try that.

[JPaganel]

Got the bike up on the centerstand and got a kid to sit on the rear fairing. Children make handy counterweights. 

Wiggled fork and wheel everywhich way and couldn't detect any signs of play. Spun the wheel. Didn't see any irregularities in the tire, but I know that doesn't mean anything.

The only anomaly was a rubbing sound that I think is from a spot on the left brake rotor. Maybe it's warped a little?

Other than that, looks normal.

[Zwartie]

I have the same thing at around 60 km/h (so pretty much the same speed). I suspect it tire related. I've had it before on my '86 and now again on my '92 and in both cases have checked all the other usual culprits, leaving the front tire as the most plausible cause. I'm running the Avon Storm ST tires on my bike. When I get to Vancouver this summer (en route to Alaska) I am going to put a fresh set of Michelin Pilot Road 3's on it and we'll see what happens. In my case, it tends to get worse as the front tire begins to cup. Maybe it even has something to do with riding most of the time in SW Ontario where the roads are flat and straight!

Good luck. I will be interested to see what you determine is the cause.

Zwartie

[andyb]

Check the tire first.  Inflation pressure as well as wear.  If it's all good, stick the bike on the centerstand and see if you can detect play in the steering (sit down in front of the bike and pull the wheel fore/aft).  Try the bounce test as well; with the front in the air, you should be able to nudge the bars and have the steering go smoothly through its range of travel and hit the stop without binding, bouncing off, or doing anything else funky.

Other things you can check if everything looks otherwise okay is making sure the forks are straight and the wheels are aligned properly with each other.

Some tires tend to do it more than others.  Particularly tires with a more sporting intent, as they often have a more triangular profile and a bit less stability in a straight line.  Sure do feel nice when you're midcorner though...


While the wheel is off, it's a good time to not only play with the bearings, but also pull the forks entirely off, give them a bath, and put some fancyfresh oil in them, as well as some new valving, appropriate springs, additional preload spacers, seals, bushings, dust caps, or whatever else fits your desire & budget.  You can also raise the forks through the triple clamps a bit if you'd like quicker steering, but there's only ~5mm or so of room before you hit the master cylinders.  If you pull the forks, take the time to take a good look at the brake lines also, especially if they're rubber and possibly original.

[ribbert]

You can also raise the forks through the triple clamps a bit if you'd like quicker steering, but there's only ~5mm or so of room before you hit the master cylinders. 

I got nearly 20mm out of mine before they hit the M/C.

[andyb]

My masters are apparently at a much different angle than yours

[JPaganel]

Check the tire first.  Inflation pressure as well as wear.  If it's all good, stick the bike on the centerstand and see if you can detect play in the steering (sit down in front of the bike and pull the wheel fore/aft).  Try the bounce test as well; with the front in the air, you should be able to nudge the bars and have the steering go smoothly through its range of travel and hit the stop without binding, bouncing off, or doing anything else funky.

Done that. Tire is worn, but looks true. I'm not really trusting that, though, as I've had car tires that look just fine do weird things at speed.

The rest of the stuff is okay - there is no play I can feel anywhere and all movement is smooth. Well, except that one spot on the brake rotor. It's weird there is a noise there, I'd have thought the brakes would pulse if there were things wrong with it.

Other things you can check if everything looks otherwise okay is making sure the forks are straight and the wheels are aligned properly with each other.

Besides just looking, how would I check that?

While the wheel is off, it's a good time to not only play with the bearings, but also pull the forks entirely off, give them a bath, and put some fancyfresh oil in them, as well as some new valving, appropriate springs, additional preload spacers, seals, bushings, dust caps, or whatever else fits your desire & budget.  You can also raise the forks through the triple clamps a bit if you'd like quicker steering, but there's only ~5mm or so of room before you hit the master cylinders.  If you pull the forks, take the time to take a good look at the brake lines also, especially if they're rubber and possibly original.

Were the budget there, I'd rebuild this bike to mint. 

The suspension doesn't seem bad to me, it's pretty firm and diving under braking is not what I'd consider excessive. I was planning on keeping the forks as is until I can get a set of post-91 ones with the larger wheel and better brakes.

And I know all about brake lines. My other bike (which is being expropriated by the Mrs.) is a 1978 XS400, which had the original 1977 brake hoses. You could feel them swell like balloons if you touched them while hitting the brakes. They also deteriorated on the inside and the rubber bits that flaked off plugged some tiny passages in the rear MC, necessitating a full rebuild.

So I replaced them with that red stuff you see here:




That's Teflon-lined, stainless steel braided, vinyl coated brake hose with stainless fittings. I got that custom made at Pirtek, an industrial hydraulic hose supplier. It was actually slightly cheaper than OEM hose. Those hoses have close to zero expansion and make brakes just awesome. Also, they oughta last near forever.

I'm planning a set of those for the FJ at some point.

[Flying Scotsman]

My 85 has an occasionall wobble 
front tire is almost slick but im sure the wobble is from the steering head bearings.If I brake hard I can feel some movement in them.There loose.Repack and retighten the nuts if there still good replace if there not.
I am puting on a new tire as well as some maintenance at the same time.I will ride another bike while I do the work.
I need a steering head wrench first as I dont have one.

[movenon]

My 85 has an occasionall wobble  
front tire is almost slick but im sure the wobble is from the steering head bearings.If I brake hard I can feel some movement in them.There loose.Repack and retighten the nuts if there still good replace if there not.
I am puting on a new tire as well as some maintenance at the same time.I will ride another bike while I do the work.
I need a steering head wrench first as I dont have one.

The castellated nut shouldn't be on very tight. The adjustment is pretty light. Here is one I made using a nut as a pattern and 4 pieces of key way stock from Ace Hardware.



The socket is a 27mm

George

[Flying Scotsman]

I will not over tighten it.
Only recently started to do it and only when hands are of the bars.
I would just snug it up but im sure it needs new grease after all its 28 years old.