A new weave/wobble....

My CB900 seems to have developed a new, mild-but-detectable weave/wobble
going through medium- to high-speed turns. It feels like the front end is
seeking a line, but just wanders back and forth without settling down. It's
only there in a turn, no sign of wobble or headshake going straight. What
are the most likely causes of this behavior?

The tires are properly aired, the front is about 50% done with no obvious
cupping or unevenness. The rear is closer to done, starting to square off
some. I've had rear tires that were flatter than this without causing a
wobble, just that funny "step up/step down" feel to entering and leaving
turns.

My list of suspects, in order:

Rear shocks. I probably should have changed these long ago. Now they're
both covered in oil and road dirt, and might not be providing any real
damping anymore. They're the stock adjustable shocks. Last time I checked
they were still available from Honda, but for a pretty penny indeed. I know
that DK sells affordable aftermarket shocks that'll fit. They're
non-adjustable, but since I never carry a passenger I see no problem there.

Swingarm bushings. Anytime I've got the bike on the center stand I give it
a shake to see if they're loose (they aren't), and a frozen swingarm would
be too obvious to miss. I doubt anyone's actually serviced the swingarm
since the bike was built. It's about time for a new chain anyway, and if
I've already got the shocks off, why not do the swingarm too?

Head bearings. Also unserviced since the beginning of time. But I do check
them for play every now and then. I don't wheelie or run over curbs, so
they shouldn't have any notching. Doing an actual service on these is
something I very much do not look forward to.

Wheel bearings. They're the sealed type, and were in good shape when I last
had the wheels off two years (~5,000 mi) ago.

The tires themselves are five years old. Could the rubber age and change in
ways that affect handling like this? It's garaged full time, and I don't
see any cracks or other signs of weathering.

Forks. Unlikely, since I overhauled them two years ago (seals, bushings,
oil). No leaks, air pressure is OK. As air forks they're a little
"sticky", but they've always been. I'll go over the triple tree and
retorque all of the clamp bolts.

Brakes dragging. Shouldn't be, since I put anti-seize on the slide pins,
but I guess they might anyway. That one's easy enough to check.

The last, least likely possibility is that every single sweeper I've ridden
in the past 300 miles is all lumpy and frost-heaved. Not impossible,
considering the DOT in question, but still....

Looks like I've got a few shop days in my future. Anything else I should
look for?

 

Your front tire's rubber is probably "dead", and it cannot absorb and
damp out small imperfections in the pavement. A matched set of new
tires will be "cushy" and the extra grip will damp out wobbles and
weaves.

If your rear shocks are worn out and don't damp the up and down action
of the
rear wheel very well, you'll notice a slow speed *wallowing* and the
handlebars will waggle back forth very slowly.

 

After five years? No.

No, you won't. You'll notice a bouncing of the back end, all spring and
no damping.

Wrong again.

 

It's not so much the rear tyre wear (though this is shot) but the
combination oif one worn and one relatively unworn tyre. I'd replace
both.

The shocks are shot, yes. Replace ''em.

Good plan.

Have you checked for nothes? I bet they have 'em.

Yes, but not in a mere five years, whatever Krsuty thinks.

Fine.

To be honest, it's most likely to be an evil combination of dodgy tyres,
worn head races, knackered shocks and a 30 year-old bike that wasn't a
great handler to begin with.

 

Some rubber compounds can be "dead" in a matter of *hours*, asshole.

Don't understand much about hydraulic shock technology, asshole?

Always remember, I'm a cracker. You can eat me.

 

Stop putting *air* in the forks. That could be a reason for why your
front tire doesn't stick well enough to go straight without weaving.

Google for "CB900 +fork springs -progressive" to find out what kind of
springs are available for the CB900, other than Progressive Suspension
springs.

The problem with PS springs is they have more coils so they take up
more space in the fork leg. That upsets the fork oil level, you cannot
use the recommended amount of fork oil called for in the owners manual
and PS cannot tell you the correct amount of oil to use because they
make the same spring for multiple motorcycles.

Oh, and don't pay much attention to "The Older Gentleman". He just
hangs around the motorcycle newsgroups looking for arguments.

Before you know it, he'll have you kissing his ass and apologizing for
somehow insulting his expertise...

 

On Thu, 28 May 2009 20:03:15 +0100, in rec.motorcycles.tech,

After 67,000 miles? I'd hope for more life out of them. And I'm intimiated
by the job. I'll have to talk myself into it.

I wouldn't know, I've got very little experience on other bikes. But it
handled a lot better this time last year, so something's wrong.

 

Only the ones my wife tells me to.

That's fair. Also easier. But it's called "preventive maintenance" for a
reason. Personally I don't wait for my camshafts to spall before I add more
oil.

 

As long as they're stock forks, I'll follow the manufacturer's directions.
I already tried running them with no air. It was NOT an improvement.

Yeah, I've tried to find progressive springs that aren't Progressive
springs. Clever bastards, aren't they?

The same oil level (distance from the top of the tube) should be pretty
close to right, or a good place to start. Some manuals give that figure.
Mine only gives the volume of oil, so I'll have to measure the level myself.

And you're dumb enough to oblige him! Both of you are smart and have
offered many pieces of good advice (and some bad), but both of you are
attention whores. If you didn't enjoy arguing in public so much, you'd KF
or ignore each other.

 

Air-assisted forks use a weaker spring than non-assisted forked would
use and
no air at all would probably tend to make the handling squirrely on
corner entry when riding vigorously.

I installed PS springs in two motorcycles before I realized what was
going on.

I tried to road race the first bike and the handling was terrible. I
had no idea what was going on to make the bike wobble so badly.

Race Tech makes all straight wound springs, but I doubt they have any
for your machine. If you're going to try running with no air, use a
pair of short compression springs to replace any spacers on top of the
stock springs.

I'm amazed at what Lowes has in all those boxes in their hardware
department..

Progressive recommended 150 mm or less of oil from the top of the
inner tube with the fork tube compressed all the way.

I tried to ignore the asshole for the first eight years he followed me
around from group to group.

He's like a fag, he can't be insulted into shutting up.

 

If you roll the throttle on, just enough to pick a couple of MPH the instant
the bike is aimed to apex, does it then settle?

Ugh, damping shot to shit and back. Won't help. Without early throttle
application, the rear will move up and down, which in turn affects the
front. Tail wagging the dog. Fairly gentle, but unsettling roll and yaw. A
small amount of throttle and/or rear brake may help to stabilise it. Try
it. New tyres wouldn't go amiss either.

Dunno if you can get Hagons, but if you can, can I recommend them to you.
Not too expensive and just plain old fashioned work.

Won't hurt to clean and repack the bearings. Check the wheels bearings too
by sticking your finger in and feeling for graunching and lateral play.

With the bike on the mainstand, get the front wheel off the ground
and -very- slowly move the bars around the centre point. Shouldn't notch at
all. Not a big job to grease and adjust. Replacing them is one of my least
favourite jobs.

See earlier comment. They can and do fail.

They do age. They -should- be OK, but at that age, personally I'd replace
them anyways. Cheaper to put new rubber on than crash the bugger.

Slacken the axle and see if the front suspension action improves. DO NOT
RIDE IT LIKE THIS. Sometimes, as you tighten the front axle, it pulls the
legs out of parallel and gives unwanted stiction. Usually because some
monkey has overtightened the axle in the past and crushed the spacer tube
slightly. Only takes a minute or so to check.

Dead easy to check.

Chain tension. If its too tight, it has a nasty effect on the handling.
Other than that, I think you've got all bases pretty much covered.

 

And those include tyres! Wow, imagine the product liability cases.

 

They're a certainty

I don't mind it on smaller bikes. I hate it on bigger ones, and getting
old taper roller bearings out is one of my most unfavourite jobs ever.

Tip: when refitting the bearings into the steering head, chill them in
the freezer and wrap rags soaked in boiling water round the headstock.
They go in easier that way.

And when fitting them to the bottom of the steering stem, reverse it.
Chill the stem and heat up the bearings.

 

In my experience knackered rear shocks bugger the handling at higher
speed, not low speed.

An ignorant poor American. Yup.

 

My advice is more accurate, more frequently

And in this instance, like I said (and someone else), it's going to be a
combination of everything or some factors.

It *isn't* going to be tyres that can "go off" in a few hours.

 

[]
In order, I'd change the shocks, check the head bearings, wheel bearings
and change the tyres. If that doesn't cure it then I'd worry.

I'd also recommend the forums at http://www.cb1100f.net as a good source
of advice about 900Fs.

If you were this side of the Atlantic I'd be trying to sell you bits of
CB900

 

Heh. Most people who own CB900s these days have them in boxes ;-)

I never really "got" the 900F. It was a long-stroke engine, for a
start, and was borderline in terms of strength, especially when tuned.
You really needed to replace and strengthen a lot of bits. I remember
Team Bike doing quite well with it in the early 1980s, but by the time
they'd finished with it they were effectively running an RSC engine.

I also found it vibey, except for the later ones which had rubber-
mounted engines. And it had that damn silly twin-camchain set-up, like
the 750 and the CBX.

Sure, it was quick for the day and a step ahead of the Kawasaki Z1000,
but nobody seems to want 'em these days whereas old Zeds and GS1000s
command quite good prices.

Oddly, I went to buy one a couple of years ago. It was an Italian
import whch had been fitted with UK-spec clocks and was in lovely
condition, but the engine number didn't match the one recorded on the
log book, so I left it alone.

 

That's what I thought, but having used the CB1100F forum to punt some
bits of this one I've discovered people restoring the damn things.

That's a polite way of saying they went "bang" a lot if you thrashed
them.

Bought my first one because it was a lot of bike for the money - £300
back in '93. Bought another one the next month as a parts bike. Blew one
then the other up in quick succession.

Bought this one on ebay a year or 2 back because it was cheap & I
thought it might make an interesting project. Don't have the time, space
or money so I'm keeping the Dymags and selling the rest bit by bit.
Might even end up with a free pair of Dymags at the end of it.
[]

ISTR a local GS1000 owner mocking my 900 until he'd ridden it, when he
went very quiet about the handling of his GS. Didn't stop him laughing
when I blew the 9 up again - he reckoned he didn't need to keep up on
the twisty roads as sooner or later he'd find me waiting on the AA van.

[]

Wise move.

 

Was it the bottom end that let go? The big ends and rods were always
marginal. So was the camchain tensioner, of course.

Years and years ago, I was asked to look at a FOAF's CB750KZ - same
engine, really. He'd bought it used, and it looked quite smart, with
an engine painted matt black, but there was something about the
webbing at the front of the cases that looked odd.

He poked it with a screwdriver, and the blade just disappeared inside
the engine :-0

Somebody had blown it up, it had put a rod through the cases, and had
been rebuilt with the holed cases, which had been repaired with
Plastic Padding. Not stress bearing, so it had worked.

What really impressed me was the guy who did the bodge had acually
gone to the trouble of moulding the original strengthening webs into
the filler. And the matt black paint was to hide it, of course.

This guy asked me what he should do. The bloke who sold it to him had
returned to his native Ireland, I remember. My advice was to break it
for parts, or if he felt brave, to 'fix' the hole he'd made with his
screwdriver and sell the bike on....

 

You really *are* an old ****, aren't you?

BTW, I'm a cracker. Eat me.