Clutch bolts ahhhhh

[kiwi cowboy]

Hi people:blink:The bike is a 86gsxr400 and the problem is the clutch bolts are breaking.
Full story-took the clutch plates out and put new ones in and because its a race bike got the stronger springs for it too but the manual says to torque up to 7-11 nm but i only got them barly to 7 when one snaped so pulled apart and got a spare bolt out of a spare bike but same thing happened when i did them up again.
The torque wrench is ok im sure of that and the bolts are breaking just were they leave the clutch boss and there is a sleave that tha bolt tightens through onto the boss with the spring round the sleave.
Been quoted 6.50 per bolt via japan witch is ok but no garantee how long to get here and am worried they might not get here before my next meet in three weeks.
The bolts have a number 7 on them witch i understand is high tensile equatint to metric 8.8 tensile but can only get them in 4mm by 40mm in cap bolt or some name like that witch have thread all the way up the bolt and im not sure weather these woul be ok to use for a meating if the others havent arived from japan as im not sure i want to trust the old bolts anymore.
cheers

[pete376403]

Put socket head screws (allen, in-hex, whatever you like to call them). the thread all the way shouldn't make any difference. You sure your torque wrench is reading n-m, not lb-ft?
The fact that you are torquing the bolts correctly doesn't mean they haven't been way overtightened by someone else in the past, either.

[Brian d marge]

Socket head screws have a higher head profile so check they fit also they have less bearing area ( which doesn't matter much )
but what savagery has been going on before to stretch and cause failure of the bolts
they don't have to be super tight as they are held under spring tension and if you are worried I sometimes use a low breaking point loctite

Torque wrenches are only a rough giude anyway

I have a few expensive ones and use em more fore racing as when they click I know the bolt/ nut is done up that all really

Stephen

[The Pastor]

stronger springs are not a good idea, i broke my clutch pressure plate because of strong springs.

i'd go back to stock strength springs.

[kiwi cowboy]

stronger springs are not a good idea, i broke my clutch pressure plate because of strong springs.

i'd go back to stock strength springs.

Whot sort of bik was that on and how mutch stronger were they?.
Mine are only 10% stronger so shouldnt be to bad.

[The Pastor]

Whot sort of bik was that on and how mutch stronger were they?.
Mine are only 10% stronger so shouldnt be to bad.
thats what mine said they were - why are you wanting stronger springs?

[kiwi cowboy]

thats what mine said they were - why are you wanting stronger springs?

Because thats whot others do to there race gsxr,s im told better for racing

[vdog]

personal experience, use stock parts or use a complete aftermarket clutch(ie basket, plates, springs and cover). This is due to the factory parts are designed for an application whereby the fitting of aftermarket springs covers fail, as do the bolts! My suggestion is use brand new springs and for good luck get some 1mm shim steel to tuck under the washers.....or bite the bullet and buy a new aftermarket clutch(like barnett) because the original is properly poked!

[Brian d marge]

ahh clutches

now don't make me reach over for the the big book * im pissed and have spent waaaay too much`h money ...don't ask (

the formula fro torque transmitted through a multi plate clutch is ...r1-r2 * radi

* what loony feeds spaghetti ,,the big round pasta shit ...to a god fairing drinking man ....


and in there somewhere is pressure and trhe number of plates

anyway the pressure has the least effect , nthe number of plates works better


but at the end of the day ,,,how the bayjesus did the bolt snap rather than the pillar

Stephen

[CookMySock]

the manual says to torque up to 7-11 nm but i only got them barly to 7 when one snaped so pulled apart and got a spare bolt out of a spare bike but same thing happened when i did them up again.I'd stop and take a step back before doing anything. Either your torque wrench is reading wrong, or you are reading it incorrectly, or else something is assembled wrong.

Don't touch anything until you find what is bogus, or you will eff something expensive.

Steve

[Yow Ling]

Is it possible you got your nms and foot /lbs mixed up?

[kiwi cowboy]

ahh clutches

now don't make me reach over for the the big book * im pissed and have spent waaaay too much`h money ...don't ask (

the formula fro torque transmitted through a multi plate clutch is ...r1-r2 * radi

* what loony feeds spaghetti ,,the big round pasta shit ...to a god fairing drinking man ....


and in there somewhere is pressure and trhe number of plates

anyway the pressure has the least effect , nthe number of plates works better


but at the end of the day ,,,how the bayjesus did the bolt snap rather than the pillar

Stephen

Dunno whot the f*^k the first bit means but the bolt probly snapped through age?the fact its got 25ml spacer in between the pillar and the bolt head so maybe a minute flex over time?or some one has done it up over tight preveiously an streched them?remembering it 23 years old.

[kiwi cowboy]

Is it possible you got your nms and foot /lbs mixed up?

Not a chance the wrench is nm or inch pounds

[imdying]

Very easy to over torque a fastener if the thread or under the head is lubed incorrectly. Very easy to snap an over torqued fastener. The torque settings you have, how do they specify the bolt should be treated?

[kiwi cowboy]

Very easy to over torque a fastener if the thread or under the head is lubed incorrectly. Very easy to snap an over torqued fastener. The torque settings you have, how do they specify the bolt should be treated?

Does'nt say anything special-it just says to tighten to 7-11 nm

[Brian d marge]

Dunno whot the f*^k the first bit means but the bolt probly snapped through age?the fact its got 25ml spacer in between the pillar and the bolt head so maybe a minute flex over time?or some one has done it up over tight preveiously an streched them?remembering it 23 years old.

the first bit is related to the fact I have a big book of Engineering facts nuts and bolts ,,you name it

its what I do

The second bit is related to the fact that my nearly ex * if it happens again she will be )

fed me some sort of Italianate food

when everyone knows after a nite on the piss ,,,you need eggs and bacon

if you want to , post a clear picture (close up ) of the break in the bolt and we can tell you how it failed also a side picture to to see if the bolt has stretched

Metal when it fails gives you a complete history of itself and they can even trace a failure of an aircraft down to a small crack millimeters long

Stephen