Front end woes.

Okay, so the front forks of the turbo are worrying me.
And they have been for some time.

The main problem is a "clunk" under braking. Not a click,
but a good solid *clunk*. (There's also a front end vagueness,
but as I am not a riding god, I'm not going to claim that's
the same problem.) Sometimes there are a couple of small
clunks rather than a large clunk.

The clunk was there before the bike's MOT, and after
the MOT, with no warnings/adviserys at the MOT. So I
don't think its steering head bearings or front wheel
bearings.

And when I looked on Saturday, the front fork is leaking
past the seal. *again*. This was not a particular surprise
as each clunk makes it feel as though the forks are bottoming
out (which I doubt) or locking in some other nasty way.

Is it possible that an airlocked antidive system could
be causing this?

Is it a fork "strip and replace knackered bits" job?
Anyone got any advice for striping GPz750 front forks?
(Apart from the obvious "get a man in")

 

If it's not wheel bearigs (easily checked) and head races (also easily
checked) then the next thing that occurs are the fork bushes. These
are the bit on the bottom of the chrome slider which sliders within
the fork lower. As they wear, you get more back<->forth movement as
the forks go up and down. However, I'd expect this to be picked up at
an MOT

Hmm. This mkes me think that perhaps the forks *are* bottoming out.
You know that the turbo uses ari-assisted forks, don't you? Try
putting some air in there (there's a valve just below the bottom yoke
on the RH fork leg). Can't remember the pressure, but around 10psi
rings a bell. It's quite a small resevoir, so a bicycle pump can
easily be used.

Not sure what you mean by this.

If you need to replace the fork bushes it is, but I think we've a fair
bit of diagnostic work to do before we get there.

 

[snip]

And the place I got the MOT done is a respectable place as well...
None of your TOG SOB-stylee dodgy MOTs there.

I had forgotten...

I shall check; is it a standard valve?

It was a vague worry about the system not being bled properly;
if the last person to bleed it didn't know about bleeding
all the way down to the anti-dive units(as they aren't
the most common bit of kit in the world), and some air was
left in there... Probably an unnecessary worry, which would
also be easily checked by going and bleeding the thing
again...

Fair enough. As the rh fork spat out quite a lot of oil yesterday
it probably needs refilling; is that a strip job, or can it be refilled
by squirting/dribbling it down the leg?

 

Cheers for the warning...

Fair enough.

hehehe.

I've had the forks out before, but instead of taking the
forks apart myself, I "got a man in" to do that bit for me.

 

It's a 750 turbo. Strange Handling comes as standard.

 

It can. The best way to measure oil in a fork is by 'dipping' from
the top, I reckon. And you don't need to worry *too* much about the
<ping> effect when removing the fork top nuts - the fork springs are
pretty weak. Which is why I put some FOAD spacers in there...

 

I'm going to need more numpty friendly instruction than that...

 

Indeed. Although more predicatable than a CX500...

 

Get a long screwdriver, or similar, and, after removing the fork top
nut, and spring, use it as a dip stick You might have to put some
gaff tape or similar on the screwdriver so that the oil makes a mark.

Don't remove both top nuts at the same time, else the forks will
collapse, possibly rolling the bike of the main stand and spoiling
your day. FO course, the best way to do this is with the front jakced
right off the ground so that there's no weight on the forks at all.

 

Yeah, the bastard.

 

Look in the BoL to find the space that should be left between the top of
the oil and the top of the fork; make yourself a dipstick out of a piece
of wire or something; dip the dipstick to check the height of the oil.

I use an insulated strand from a piece of twin+earth, bent to 90deg at
the top, notches cut in the insulation to show the min+max.

 

Aye, you suddenly get a realisation of just how much the fuckers really
weigh.

--

Dave

GS 850 x2 / SE 6a
SbS#6? DIAABTCOD#16 APOSTLE#16? FUB#3
FUB KotL OSOS#12? UKRMMA#19

 

Using the patented Mavis Beacon "Hunt&Peck" Technique, Eddie
<> typed

(of fork oil)

*Nice* idea. Filed.

 

I use the nice adjustable alloy attachment for my Mytivac pump that I
have for exactly this purpose.

--
Lozzo
ZZR1100D, GPZ500S, CB250RS x3
BOTAFOT#57/70a, BOTAFOF#57, two#49, MIB#22, TCP#7, BONY#9,
ANORAK#9, DIAABTCOD#14, UKRMT5BB, IBW#013, MIRTTH#15a/16,
BotToS#8, GP#2, SBS#10, SH#3, DFV#14, KoBV#3.
Url for ukrm newbies : http://www.ukrm.net/faq/ukrmscbt.html
www.mjkleathers.com

 

Lozzo wrote:
[ fork oil height ]

Oh, ah, forgot about that. Except I use a piece of tubing taped to a
straightened coat hanger.

 

[snip]

Followup from a brief investigation in the dark last night.

There was square root of naff all air pressure in the forks.
Ah. That'll've been working the forks a little harder than
required then...

A brief move around this morning shows that the clunk is
still there. But as one of the forks has a different amount
of oil in it to the other, that it's a great surprise...
I'll get the oil levels level at the weekend.