FKE 12.9 stamped on top

[Y50 VET]

Hi
Does anyone know about bolts??

I have a blot on the starter on my bike it had sheered off three times

It’s a standard Allen key type with the letters FKE 12.9 stamped on the top dose this refer to the tensile strength or is it a safety sheer bolt??

Sam

[franv8]

Sam - FKE is the manufacturer and 12.9 is the grade of the bolt (tensile strength) - it isn't a safety sheer bolt per se.

[franv8]

By the way if you keep snapping it there is probably a problem somehere - are the other mounting bolts present/tight?

[Y50 VET]

Exactly my thoughts as well, it’s a 1000 cc V Twin so very high compression and the starter is labouring to flick it over, the bolts are not lock tightened in and this is the third time the starter sprag assembly has failed these bolts are holding the housing locked onto part of the flywheel
Any idea if there are higher tensile bolts available and what this equates to ie normal or high tensile??

Sam

[Y50 VET]

Seems there is a problem where the starter flicks over too slow and this has increased torque its too much for the blots to take, seems a bit stupid if you ask me,

Sam

[te51cle]

If you were in Basingstoke I'd suggest dropping in to Hampshire Bolt & Tool. Whenever I've needed anything like that for my bike they've always been happy to advise and supply even one-offs even though they're an indiustrial-sized outfit. I'm sure there must be similar specialist suppliers in your area - time to trawl the yellow pages ?

[Gixer]

Good luck with getting stronger bolts. If its anything like my previous Yamahas all the bolts where one-off unique non-standard sizes/threads (made of cheese)which made getting replacements a complete mare - even though at the time I knew an MD of a company that made nuts and bolts for several main car builders

[boosted ls1]

Seems like a very hight tensile top quality bolt but brittle as well. I think you have a problem elsewhere, in other words the bolts are fine.

Boosted.

[stevieturbo]

12.9 is the highest spec bolt you can get, aside from specials, such as ARP, or aero grade stuff.

[Y50 VET]

thanks i will drop in and see if the parts have arived and get it back together for the weekend
Sam

[ZR1cliff]

The cam bolts i am using are 12.9's,they are toughies,Sam have you tried another make or batch incase youve got a bad batch of bolts there.

[Y50 VET]

i think its a torque issue, i am told the bike is back together and i will go and get the old parts at the same time and have a close look, with a lower flick over the torque is up and that's what is doing the bolts in, i think

Sam

[ZR1cliff]

Sam if it helps to give an idea of what torque value a 12.9 bolt can take,the one i have in front is around 10-15mm thick and is torqued to 25nm and 80-85 Degrees, i think this translate to around 120-130lbs ft (taken from another forum),if anyone knows better pitch in.

[stevieturbo]

If you are shearing a 12.9 bolt, you have other issues. the 12.9 does refer to its sheer strength as far as I know.

The bolt must be coming loose, or fatiguing some way.

Think about it. Many cars only have 2 say M10 bolts holding the brake caliper on, and look what they do.

or a propshaft with say 4 x M8 bolts. In sheer these bolts are extremely strong.

I think the 12.9 actually means it would take 12.9 metric tons to shear it.

Doing a websearch. Not sure how useful these are, just linking what came up for "fastener shear strength 12.9"
www.co-design.co.uk/dpg/bol/bol6.html

www.tech.plym.ac.uk/sme/desnotes/desbolta.htm

www.mcfly.org/screw

[Y50 VET]

The bolts as listed on the blow up are Hex Socket Screw M8x16

www.co-design.co.uk/dpg/bol/bol6.html

useful link about torque ratings etc./////

Hi thanks for the tips everyone, I have found a Aprilia Racing sight in the USA that also quite interesting, I just picked up the bike after its been re built and seems to be running fine now. It was also suggested that one of the parts was walled out and not quite sure if they mean the holes are oval or the part is twisted?

Sam

[franv8]

Bolts in many of these applications are designed to work in tension (even wheel bolts) - they are notoriously bad in pure sheer. To deal with sheer forces parts are designed to be clamped together (e.g. propshaft flanges, wheel flange to hub flange interface etc.) - hence the importance of making sure these surfaces are very clean before you put them back together (and free of paint too).