WTF caused this?!?

[mszilves]

So I go to start the bike up tonite, and get a loud "bang/thud", scared the cr*p out of me... so right away I stop cranking. Go to start her up again, and same thing, now followed by a LOUD grinding sound. WTF I thought, the fizzer has been running perfectly, no issues whatsoever.

First thing I do is take off the airbox to see if there is any gas pooled (leaking float valves, but I highly doubt it) in case it's hydrolocked. Nothing, nice and clean valves.

Next I go to take off the starter clutch cover to see what's going on... I find this: now does anyone know why/how in the world this happened, and what might have caused it? I notice that one of the reductions gears is worn, would that be enough? I'm at a loss... and I can't even start or run the bike like this! So at the same time, I guess I need the crank starter gear, and the worn reduction gear? Will I even be able to source these parts from bikebandit etc?

Broken teeth




Teeth sitting in cover


Worn reduction gear

[demon_knight69]

wow, WTF?! that's odd that that would happen all of a sudden. when my transmission finally blew up last year i knew it was coming. i had the third gear grinds and accidentally shifted into third and gave it a handful of throttle. i too got the loud bang followed by nasty rattling sounds. i limped it home and when i got to taking it apart found several broken teeth.

i don't see how yours would have done that though. seems like something would need to be way outta sync or something got in between some teeth.

[mszilves]

wow, WTF?! that's odd that that would happen all of a sudden. when my transmission finally blew up last year i knew it was coming. i had the third gear grinds and accidentally shifted into third and gave it a handful of throttle. i too got the loud bang followed by nasty rattling sounds. i limped it home and when i got to taking it apart found several broken teeth.

i don't see how yours would have done that though. seems like something would need to be way outta sync or something got in between some teeth.

Yeah, really weird... I have absolutely NO issues with my tranny, and the bike runs awesome. This pretty much came out of nowhere, and before started throwing parts at it, I wanted to figure out why this may have happened. The only thing I can think of is the wear on the reduction gear.

[reelrazor]

A) how's the pilot bearing in the cover for the worn gear?

B) how often are you changing your oil? (that's a splash lube area)

[csofos]

A) how's the pilot bearing in the cover for the worn gear?

B) how often are you changing your oil? (that's a splash lube area)

+1000

[mszilves]

A) how's the pilot bearing in the cover for the worn gear?

B) how often are you changing your oil? (that's a splash lube area)

The pilot bearing looks fine. I'm pretty religious about changing my oil, so every 5000km (3000 mi). That's why I'm stumped, because otherwise the engine should be in perfect condition.

[yamaha_george]

wow, WTF?! that's odd that that would happen all of a sudden. when my transmission finally blew up last year i knew it was coming. i had the third gear grinds and accidentally shifted into third and gave it a handful of throttle. i too got the loud bang followed by nasty rattling sounds. i limped it home and when i got to taking it apart found several broken teeth.

i don't see how yours would have done that though. seems like something would need to be way outta sync or something got in between some teeth.

Only needs one tooth to shear then get between the others its like skittle after that
Y-G

[mszilves]

Only needs one tooth to shear then get between the others its like skittle after that
Y-G

So George, you think it was likely just metal fatigue on the flywheel gears?

[haunter]

thats my guess


its old man......

[sweekster]

I was gonna say the worn teeth on the reduction gear caused a tooth to get skipped and then all hell broke loose from there.

[thatkid]

On the bright side I have you covered! PM me your address again and I'll try and get it shipped out USPS before work. Otherwise I'll do it UPS at work.