Weird thunking from a 2000 fireblade

Morning,

I have a problem with a 2000 fireblade I've had from new which
has 20k miles on it. When I'm banked in a corner at slow speed
(mini-roundabouts, that kind of thing) I'm getting a thunking
from the bike. It's not something I can hear but something I
can feel through the left peg (not the right one). The frequency
of the thunking is wheel speed as much as I can judge. I also
get the thunk if I stop, pull in the clutch and then pull away
and within a second or so I get a single thunk and this happens
when I'm upright, if I'm banked I get the 'normal' series of
thunks. The noise is always more pronounced when the bike is
warmed up towards the end of my commute.

The chain is 5000 miles old (first chain change at 15k miles)
and looks in good nick and there's no obvious wear on the
sprockets. I put in a new cush drive about a month ago as the
old one was shafted and causing horrible gearchanges. The bike
seem extraordinarily sensitive to chain adjustment (always has
been) but the problem didn't change when I adjusted the chain a
couple of days ago. Apart from the thunking there's no apparent
change to the way the bike rides. Looking through the oil filler
hole there's no obvious notching of the clutch basket but you
can't obviously see that much.

Given the frequency of the thunk my first suspicions were that
this was an early sign of failure of the rear wheel bearings but
would very much appreciate a second opinion so I can fix it
quickly and not have to resort to taking the train to work.

Thanks for any help.

Regards,

 

Sounds more likely to be the cush drive than the bearings. SWK will be
along shortly, but I'd probably try and distinguish by raising the
rear wheel and trying to wobble by hand - if it's just
forward/backward movement it'll be the cushes, side-to-side is the
bearings.

--
_______
..'_/_|_\_'. Ace (brucedotrogers a.t rochedotcom)
\`\ | /`/ GSX-R1000K3
`\\ | //' BOTAFOT#3, SbS#2, UKRMMA#13, DFV#8, SKA#2
`\|/`
`

 

That's what it seems to point to. Can you feel any play in the
rear wheel when it's off the ground? Try removing the chain and
spinning the rear wheel by hand. If it's that bad you should feel
it through the spindle.

riccip

 

No, there's no play in the rear wheel.

The problem, I think, is that there are 3 bearings in the rear wheel,
2 in the wheel itself and one in the sprocket plate that slots in the
cushdrive. My suspicion is that as I can only feel the thunk through
the left peg the bearing in the cushdrive plate has gone south and
transmitting the thunk down the chain to the front sprocket which is
next to the left peg. I guess dirt in the bearing when the chain was
changed, when I installed the cush drive or on one of the occasions
the rear tyre was changes or the grease in the bearing may have just
washed out. Does that sound feasable?

Anyway, I'll get the wheel off tonight and see if any of the bearings
are notchy.

My worst fear was that the gearbox has died and it always has felt as
clunky as hell (thank you mr honda) and the chain only has to be a bit
slack for it to feel terrible.

Thanks,

 

Took the wheel off, removed the chain and put the wheel back
on and the wheel spins freely with no noises. Took the wheel
back off and felt the wheel bearings and they are smooth but
the sprocket carrier bearing is slightly notchy. No tight
spots in the chain and the front sprocket doesn't have any
play in it. Guess it must be the sprocket bearing starting
to go so I'll change that and see if there's any difference.

Cheers,

 

Mark says...

OK, this is going to sound really stupid, but when you have the bike on
the paddock stand, make sure the rubber cups aren't hitting the
sprocket nuts when you spin the wheel.

I know it's not relevant to your situation, but it may stop someone
else from doing what I very nearly did when this happened on my Elly's
rat-bike. I came very close to replacing the rear wheel bearings for
her.

 

Lol, done that and then spent minutes trying to get it in neutral so
the wheel would go around.

It was fine on the stand, just felt the notchyness rolling the inner
bearing race with my finger.

It is noisy just rolling it up the drive in neutral but then it always
has.

Regards,

 

My Elly's? I fort Elly was Pip's?

--
Lesley
CBR600FW
SBS#11 (with oak-leaf cluster)
BOTAFOT#101A UKRMHRC#12
BONY#54P BOB#18
Real burds don't take hormones, they rage naturally

 

SP says...

When I was writing it I thought it might have been my 9R, then I
remembered it was Elly's rat so changed *most* of the post.

 

It is a menage a trois, after all.

 

Using the patented Mavis Beacon "Hunt&Peck" Technique, SP

ITYF Elly is Elly's. ;^)

--
Wicked Uncle Nigel - Manufacturer of the "Champion-105" range of rearsets
and Ducati Race Engineer.

WS* GHPOTHUF#24 APOSTLE#14 DLC#1 COFF#20 BOTAFOT#150 HYPO#0(KoTL) IbW#41
Enfield 500 Curry House Racer "The Basmati Rice Burner",
Honda GL1000K2 (On its hols) Kawasaki ZN1300 Voyager "Oh, Oh, It's so big"
Suzuki TS250 "The Africa Single" Yamaha GTS1000

 

At least that's what they let her think

--
Veggie Dave
UKRMHRC#2 BOTAFOF#08
IQ 18 FILMS http://www.iq18films.com
Extreme Racing http://www.veggie-dave.co.uk
Toxic Shock Syndrome Gets More Girls Than Me

 

Are you the lozzo I sent some spare rd350 gaskets to a few years back?
Stiil got the rd?

Regards,

 

Mark says...

Does that Lozzo owe you money?

He's a fucker for that is the old Lozzo.

 

Ah, guess not then. No, no money, just some spare gaskets in the post.

 

Ah, I see..it makes sense now. )

--
Lesley
CBR600FW
SBS#11 (with oak-leaf cluster)
BOTAFOT#101A UKRMHRC#12
BONY#54P BOB#18
Real burds don't take hormones, they rage naturally

 

Mark says...

Same Lozzo, thanks for the gaskets. I think I owe you a drink though.

I don't have the bike any more, sold it to Reynard of The Wirral. I
went onwards and upwards, as they say.

 

Morning,

Finally got around to sorting this out. I ordered the bearings and the
day
they were delivered the bike suddenly stopped making the noise...
fecking
thing is like my kids, cries until they get to the doctors then perk
up.

So I left it and a low rumbling started from the back end that slowly
got
worse over a week so I changed the bearings when I serviced the bike.
Now
it's completely quiet again so I guess that must have been the problem.

My suspicion is that the sprocket carrier bearing must have got some
dirt
in it as that was the one that was slightly notchy. The bearings in the
back wheel felt perfect but I put the new ones in anyway. Hopefully
these
will last a bit longer than 20k.

Regards,

 

B*llocks, it's happening again.

I seem to notice it more when it rains and I'm not using as
much throttle. It feels like something is taking up play when
initially accelerating slowly and then I get this thunk-thunk
through the left peg if slowly cornering.

Any ideas?

Thanks,

 

Sounds like some sort of lash in the drive train. Check the cush
drive.