Broken Crank

[steve200b]

Any ideas as to the reason for the nose to break of the crank?

The motor was balanced etc. very lucky we found it before more damage was done

[XKLABA]

Did it have an extended oil pump drive fitted ?

[steve200b]

Yep

[89CAL]

Perhaps it was fitted incorrectly. Too much heat in the crank or retaining bolts/screws not installed properly

Just a random guess seen as it sounds like you had a crank collar installed and thats where it broke. Better photos of the fatigue point?

[turbo76lx]

What brand balancer, ATI, Ross?

[Adriano]

Factory balancer bolt and washer?

[steve200b]

Ross balancer and factory bolt with washer

[Ben C34]

That sucks man.

I assume it would have bent some valves. ..

Could it have been something silly like the bolt bottomed out in the crank?

Edited June 1, 2014 by Ben C34

[steve200b]

Very lucky made 480kw with some wheel spin and then lost 100kw and then started looking for the issue and found that. No other damage done lucky. Motor out today for another crank and some rings etc then back on the road in a few weeks

[steve200b]

[89CAL]

Ill look at my wear guide later if I think of it but looks like it has fractured over a longer period of time. How long was this crank in use in this form for? And what Is the previous history of this particular part of the crank? (Heating to remove gear, crank collars on off etc)

[steve200b]

Was in a low km one owner r31 before this build. It has had two years of abuse with no issues. Just thought it was a strange place to break

[SimonR32]

Ross balancer and factory bolt with washer

Funny that...

[steve200b]

Funny that...

I assume you use something different?

[Badgaz]

that happened to one of the drift guys in NZ but it was the other end...his was because he had too much weight on the back of the crank triple or twin plate clutch i believe.

[SimonR32]

I assume you use something different?

Yes I do after seeing so many issues directly related to Ross balancers.

To give you an idea I know a crank that was pulled out that was bent in exactly the same spot with Ross balancer.

[R32 TT]

Yeah not a fan of them either...

[GTRPSI]

Looks like the woodruff key is at a slight angle and has moved inwards causing extra stress on the cranks snout.

Id say the balancer was moving on the crank and the vibration caused it to crack.

Ive heard similar about Ross dampners, that why we went with a ATI one from the start.

[steve200b]

Thanks for the feedback I will change the balancer and see what happens this time

[ido09s]

not the first one i have seen and of all the ones i have seen they have had external oil pumps. Must just be a weak spot in the standard crank that doesnt like the added pressure of a oil pump belt