clunk

[cookie]

i know it's hard trying to diagnose something via these pages, but have a go at this:

my newly acquired R80G/S mono. when i pull away from a standing start, i often get a clunk from down below somewhere, just as i release the final bit on the clutch lever.
the bike's already moving by then, so any slack in the transmission must be taken up.

only happens from a standing start.

if i slip the clutch a bit more than usual, it doesn't do it.

no "jerk" when it happens, but i can feel the clonk through the footrests.

riding slowly in gear and opening and closing the throttle can't replicate it, so i really don't think it's transmission lash.

gotta admit, i can't really think what it could be. best guess is something taking up end float as power comes in. maybe the clutch pushrod provides thrust up to that point?

anyone got any pointers?

 

[BegesRus]

I fixed mine with earplugs

 

[cookie]

I fixed mine with earplugs

did you insert them through the gearbox filler, or wedge them under the UJ bellows?

 

[Kenny]

Feck me, you've only had it 5 minutes and its knackered

As per PM

 

[cookie]

Feck me, you've only had it 5 minutes and its knackered

As per PM

yeah, my fault for riding it

 

[Steptoe]

Could be the shock absorber in the driveshaft or the shock absorber in the gearbox input shaft or the clutch plate arms working loose and moving where they attach to the friction material.

 

[Rob Farmer]

Mine does it as well and I've got a rebuilt gearbox, new clutch and no play in the driveshaft. I've assumed it's the clutch pushrod bearing sticking in the gearbox. It's never got any worse so I haven't worried too much.

 

[cookie]

this one has a new clutch, and a rebuilt box, but how many people would replace the shock absorbers?

i'm thinking i might as well leave it until something falls off and makes itself known. if it ever does

thanks for the opinions

 

[(RIP) Kaister]

shgocks topping out ?

shock rubbers knackered ?

subframe loose ?

centrestand moving ?

head bearings loose ?

rear brake plate loose ?

 

[cookie]

shocks topping out ?

nope

shock rubbers knackered ?

new shock.

subframe loose ?

don't think so.

centrestand moving ?

not impossible

head bearings loose ?

i had a little bit of judder when applying (even the OEM), "brake". headstock top nut was finger tight, but i fixed that

rear brake plate loose ?

quite like that idea, and i'll check, but i reckon it's one of steptoes suggestions. hard to be 100% sure, but clonk seems to come from the gearbox area.

 

[Rob Farmer]

but how many people would replace the shock absorbers?

I have on mine

It could be a groove in the gearbox end cover causing the bearing to stick when you let the clutch out. I've had that before.

 

[newbuild100]

Just a thought. When on the main stand, my Gs was making awful grating nosies from the shaft/gearbox area, when the rear wheel was spun. I couldnt suss out what is was (gearbox bearings/swing arm not central etc etc were all checked).
I undid the boot on the output shaft/swing arm and noticed that the bolts holding the g/box shaft to the drive shaft were hitting the bottom of the drive shaft housing.
As i had checked (twice) that the swing arm was central in the frame, i knew it wasnt that. Shining a torch up to the underneath of the frame, i noticed the top eye of the shock absorber had sheared off !!!!!!!!!!!!!!!!!
The remainder of the shock, minus the eye, had wedged itself in the cleat of the frame.
I dread to think what would have happened if that cleat hadnt have been there.
The aftermarket shock WAS replaced by the makers FOC but quite scary eh ?

Metal underpants anyone !!

 

[Kenny]

Just a thought. When on the main stand, my Gs was making awful grating nosies from the shaft/gearbox area, when the rear wheel was spun. I couldnt suss out what is was (gearbox bearings/swing arm not central etc etc were all checked).
I undid the boot on the output shaft/swing arm and noticed that the bolts holding the g/box shaft to the drive shaft were hitting the bottom of the drive shaft housing.
As i had checked (twice) that the swing arm was central in the frame, i knew it wasnt that. Shining a torch up to the underneath of the frame, i noticed the top eye of the shock absorber had sheared off !!!!!!!!!!!!!!!!!
The remainder of the shock, minus the eye, had wedged itself in the cleat of the frame.
I dread to think what would have happened if that cleat hadnt have been there.
The aftermarket shock WAS replaced by the makers FOC but quite scary eh ?

Metal underpants anyone !!

Just goes to show how accidents can happen Spill the beans, what make was it that failed?

Mr Cookie Esq has a brand new OE one fitted

 

[newbuild100]

It was a manufacturer that began with "H" and ended in "agon". !!!!
I have to say they were very good about it.
I was at a workshop 50 miles away some work done on the bike at the time. I rang Hagons and they hinted at "weld the shock up to get you home" which we did. They then replaced the item without any fuss. I could have let the bike sit in the workshop, awaiting a new shock to turn up but getting home seemed like a better option.
I wouldnt let this put me off buying another Hagon, and they did seem genuinely shocked at the failure

 

[cookie]

Could be the shock absorber in the driveshaft or the shock absorber in the gearbox input shaft or the clutch plate arms working loose and moving where they attach to the friction material.

so, having finally got around to checking out the parts diagrams for the two mentioned shock absorbers, would you say that the noise is potentially the result of weak/broken springs or worn cams, and does it need investigating?

i find it rather annoying the moment, but could probably learn to live with it if it's non fatal.

 

[Ogmios]

any vibes through the footrests?

coz mine did / does the 'clunk'.*
then this vibe through the pegs gradually crept in.
now i'm (at some feckin point - when i can! ) stripping it to look at the front U.J and output bearing (?) and work backwards toward the bevel box.
just praying it's not the gearbox / leaving that til last.

*not trying to alarm you - mine had the clunk from when i got it til now - approx 30k miles i think - and only recently does it vibe through the pegs.
Disclaimer;

i could be talking total unhelpful bollards....

 

[cookie]

any vibes through the footrests?

coz mine did / does the 'clunk'.*
then this vibe through the pegs gradually crept in.
now i'm (at some feckin point - when i can! ) stripping it to look at the front U.J and output bearing (?) and work backwards toward the bevel box.
just praying it's not the gearbox / leaving that til last.

*not trying to alarm you - mine had the clunk from when i got it til now - approx 30k miles i think - and only recently does it vibe through the pegs.
Disclaimer;

i could be talking total unhelpful bollards....

no separate vibe, but i can usually feel the clunk.

having now seen the parts drawings, my guess would be that it's the drive shaft shocker rising up the cam under load, then snapping back, clunk, but i've no previous experience of the clunk or even seen the parts involved.

 

[Kenny]

If I recall rightly...the shaft 'shocker' is an 'effin strong spring so I wouldn't worry about it and just enjoy the ride.
"They (nearly?) all do that Sir "

 

[Steptoe]

no separate vibe, but i can usually feel the clunk.

having now seen the parts drawings, my guess would be that it's the drive shaft shocker rising up the cam under load, then snapping back, clunk, but i've no previous experience of the clunk or even seen the parts involved.

I've got the special tool to dismantle the shaft if you need it.

 

[cookie]

I've got the special tool to dismantle the shaft if you need it.

maybe one day. thanks for the offer