Crankshaft primary gear damaged?

[MrAfgatra]

Hello,
I noticed some cracks on the crankshaft primary gear. I assume this is something serious and it requires crankshaft replacement? Am I right? Is it worth it or I should just start looking for an engine?
My bike: fz6 s2 2007; 55k miles

 

[Gary in NJ]

I think that gear is at a high risk for catastrophic failure (it has already failed). I would think that a used engine could be sourced for the cost of the parts alone to repair the damage. The question of why this gear failed is of interest. I wonder if the engine experiences detonation or some other anomaly that causes uneven movement at the crank shaft? Is this a modified engine or one where there is an aftermarket engine controller? Are you running a significant amount of spark advance or high compression pistons?

 

[Motogiro]

Could that be caused by excessive early down shifting with out rev matching? Forces would be in the same direction.

 

[TownsendsFJR1300]

I believe this is the gear you pictured, correct (below)?

Yamaha Motorcycle 2007 OEM Parts Diagram for Crankshaft Piston | Partzilla.com

Buy OEM Parts for Yamaha Motorcycle 2007 Crankshaft Piston Diagram

www.partzilla.com

Is that a gear adjacent to it that it's BARELY TOUCHING?

Agreed 100%, it's a matter of time before it grenades but, if you can, please answer what gear is super close to it/ adjacent to it and if it appears it should be fully meshed.. If so, something major already failed.

** What led you to look into the engine cases, apparently an issue?

.

 

[MrAfgatra]

Thanks for answers. I'm as suprised as you guys. It's not my first bike, but it's the first time I stumbled upon such issue

I believe this is the gear you pictured, correct (below)?

I'm not sure to be honest... This is the gear that is "connected" to the clutch housing

** What led you to look into the engine cases, apparently an issue?

I wanted to inspect clutch discs wear and, just out of curiosity, looked inside the engine.

I wonder if the engine experiences detonation or some other anomaly that causes uneven movement at the crank shaft?

I didn't notice any of this, but the clutch was always quite noisy when engaged (the noise is especially noticable when shift lever is on neutral)

Is this a modified engine or one where there is an aftermarket engine controller? Are you running a significant amount of spark advance or high compression pistons?

No modifications were done to the engine

Could that be caused by excessive early down shifting with out rev matching?

I always use rev matching when shifting, but maybe the previous owner didn't (I have the bike for 2 years)

 

[TownsendsFJR1300]

So it's the gear attached to the clutch pictured below (part #1)?

If it is indeed the below part, that clutch is absolutely replaceable..

Can you take a pic, slightly back some showing the ADJACENT GEAR it mesh's with as well as a close up of that gear (inspecting for damage to that gear).




If it is indeed

 

[MrAfgatra]

Sorry I wasn't clear. The clutch gear is adjacent to the damaged one. I'll take more pictures later today

 

[FinalImpact]

I'd guess the clutch blew up at some point in its life and it digested said clutch bits through the drive and driven gears.
This explains the noise too. The gears have been slightly displaced thus making the noise.
You can pull the clutch drum for a better view keeping in mind the drum has a chain to the oil pump down below.