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Fitting Springs to Stands
To stretch a spring into place without damaging
it by over-stretching often seems a daunting task. Try removing one
of the centre-stand bolts and slackening the other, fit the spring
at both ends and use the stand as a lever to align the holes for the
missing bolt.
Make a strong hook from an old spoke (very tough wire, spokes), the
curl of the hook need only be about a quarter of an inch, pass the
other end through a bar or a box spanner for a "T" handle.
This will enable you to exert great pulling force and you can twist
the eye of your hook out of the spring-eye once located.
With the rear suspension unit held by it's lower eye in the vice and
the spring pre-load adjuster backed right off, you can pull the shroud
or spring down to release the spring retaining collets. Wipe the damper
rod clean before plunging it up and down to check the damping action.
It should descend easily and strongly resist being pulled up. Any
free-play indicates air, i.e. a loss of damping oil indicating a leaking
seal.
Some after market hydraulic units may be dismantled for servicing
e.g. Koni or Marzochi. If you do this without an instruction sheet
I strongly recommend that you get a large clean sheet of paper and
draw an "exploded diagram" of the thing as you take it apart.
Some of them have lots of shims spacers and bleed-hole plates, note
also which way round the various cups and seals are fitted. If you
don't do this and end up with an incomprehensible jigsaw puzzle, don't
say I didn't warn you!! They are not always as simple as you would
imagine.
Regarding spares, if unobtainable, I've made new damper rods out of
stainless steel bar, oil seals will be at your local bearing stockist.
Fortunately precious little else wears. Auto transmission oil (non-frothing)
is a good substitute for specialist fork oils. If the unit is non-serviceable
such as most Girling or Armstrong types you have little option other
than to replace it.
Swing-arm Bushes
BSA used bonded rubber in their 1950s B and A models and they rarely
need attention. If necessary replace them by the same method as suspension
bushes. Most other manufacturers fitted bronze bushes. Some fitted
Grease nipples, many did not.
Of those who did, many only fitted one, and it was often inaccessible,
either below the bike or behind the mudguard. The better ones are
located at the ends of a hollow swing-arm spindle, one either end.
It makes sense to add grease nipples during your rebuild if possible,
because replacing the bearings is tedious, and bronze bushes should
be reamed in-line after fitting to ensure correct alignment of the
swing-arm. You will need a local engineer to do this, expanding reamers
of this size are expensive and not generally found in the home workshop.
I certainly don't have any. If you persevere without grease nipples,
don't just smear components on assembly, smother 'em! (Wipe the excess
off the outside though.)
Frame
Frames that are bolted together as front and rear sections often have
a hollow sleeve in the joint. This is to positively locate the parts
being joined and also serves as insurance in case the through bolt
should slacken - (it also makes a handy attachment point for a sidecar
strut). It will be a tight push-fit, and may be removed to enable
the frame to enter a blasting cabinet for example. If you remove it,
please label it clearly, don't lose it!
Renovation of Frames
Pay particular attention to areas of stress. Examine older frames
for signs of cracking below the steering head, where the rear sub-frame
joins and at engine or swing-arm mounting points. Get expert attention
if necessary.
While you're at it, pay attention to wear at the centre-stand mounting
(very few restorers do). Re-build lost metal with welding, not forgetting
to make mounting eye-holes round again. Treat the stand itself in
the same way. Have a local engineer ream out worn holes and make up
new sleeves to match. Do it while you have the frame stripped bare,
you won't be able to rectify it later. Most motorcycles when new rose
easily onto their stands, they should today. Welding lumps on the
feet of the stand later will not cure the problem of wear. Why run
the risk of a hernia later, repair it properly now!
Alignment
Obvious Defects can be seen by eye, and frames can be jigged straight,
a prowl through Yellow Pages will find a dealer with a frame jig.
If you're not sure. you can check it relatively easily, using a home
made indicator, but you will need to remove the front forks and steering
yokes.
Tools Required
Hole-Saw for woodwork
Spirit Level
Threaded Bar, a long length of 10mm diameter and nuts
to suit (less prone to bend than 6 or 8mm)
With the hole-saw, cut two discs of hardwood of suitable size and
gently taper one edge to fit firmly into the headstock of the frame.
There will be a hole in the centre of your wooden plug, enlarge it
so that the threaded rod is a firm fit through it. Pass the rod through
the steering head and "screw" the wooden plugs up to to
locate it centrally. Place the spirit level across a horizontal part
of the frame, (chock the frame until it is level).
Now stand back from the front of the frame and check by eye that your
rod appears vertical. A deviation of 1 degree from vertical is equal
to about 3/16" per foot, so if your steering head is three and
a half feet from the ground, your front wheel will b half an inch
out of step with the rear.
Forks
Enough has been written about the advantages or otherwise of telescopic
forks, so I'm not about to add my penn'orth. I've had many bikes in
my time with "girders", "teles" and a variety
of types of trailing and leading link forks. Personally I like the
ride given by Earles-type forks and have experienced them on BMW,
NSU, Zundapp and a couple of hybrids too, but there's no denying that
telescopic forks are neatest, and perform well enough to be more than
satisfactory to 99% of riders.
A word about Earles-type forks. These are effectively a rear swing-arm
pointing forward, pushing the wheel rather than trailing it. Worn
pivot bushes or a slack pivot spindle will cause the front wheel to
wobble horribly. Wear in a telefork is not so noticeable in its effect.
Keep the front axle firmly tightened (but never over- tight), it forms
an integral part of the rigid structure of the unit, as does the mudguard
top support or "brace". Never over-tighten pinchbolts, they
are usually only a "double check" device, and in the case
of Norton forks, you'll surely crack the casting if you're heavy-handed.
An early indication of a bent fork leg is if you have to twist or
force it into place to fit the wheel spindle. Remove the wheel and
rotate the fork end to see if it "strays" away from a central
point. (Designs with captive springs prevent rotating the fork end,
but you can slacken the top nut and pinchbolt in the lower yoke to
rotate the whole leg.) Slightly bent fork legs may be straightened
in a press, ask around local dealers, it's not expensive.
Where sleeve nuts form a part of an oil seal system (as for instance
with BSAs) they often used fine waxed string in the threads to render
them oil tight. If you must be authentic, the string used to close
bags of dog biscuit makes a good alternative (and if you can pick
the end that undoes it in one pull - like Molegrip - you're cleverer
than me!) PTFE tape is quicker.
PTFE tape will also in some cases enable a stripped thread to grip
again. I've even used it successfully on exhaust port threads on a
Vincent. Don't overfill fork legs with oil, it will only find it's
way out sooner than expected.
| Comments |
| Marriot 5th March 01 | What a brill detailed story. It's fantastic. Now I'm going to have a go at mine.
| | David Harriss 3rd January 02 | Iam about to replace the fork oil seals to my 1984 suzuki gs 550e when i noticed the existing seals are not in the orientation i would expect. ie the open end is facing upwards.
i would be grateful for guidance on the correct fitting of the seals. the haynes manual i have does not show the oil seals.
Regards,
Dave Harriss.
| | Pete Causer 14th February 02 | David, the seals fitted to quite a few modern machines are of the double- or triple-lip type. Double lip seals, like single lip ones, are usually only open on one side, with two sealing lips being moulded into the inner circumference. These should always be fitted with the open end inwards, i.e. on the side where the oil is!
Triple lip seals can take two forms, the first having a third (dust wiper) lip simply moulded on the outer end of a double lip seal. Treat this as a double lip type. The other type actually has the third lip properly reinforced with a spring pulling the sealing edge in towards the stanchion or shaft to provide a more positive seal. This should be fitted with the deeper (double lip) side towards the oil.
Remember too that for road use, the majority of forks are fitted with a secondary dust seal outboard of the oil seal, sometimes (e.g. Kawasaki GT550 and 750) replaced with rubber gaiters or metal shrouds. These should not be removed unless you are prepared to clean the forks and seals at the end of every day's riding since the ingress of dirt will lead to rapid failure!
| | Pete Causer 15th February 02 | Another handy tip regarding fitting of stand springs where at least one end of the spring is a hook or loop whch has to be located over a peg of some type.
Take a large cross head screwdriver, Phillips #3 will usually do nicely. Thread this through the spring end and locate one of the grooves of the working end of the screwdriver on the peg that the spring has to hook over. Lever the spring up with the driver and you will be surprised just how easily the spring slides down the shank of the driver and slips straight into position on the peg without you having to swear at it!
| | d ricks 23rd December 02 | I am looking for a spacer to replace my speedometer drive unit on my 95' zx6r. I was hoping that someone produces a manufactured captive wheel spacer for this purpose. Any advice would be appretiated. Thank you.
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