Camshaft issue

[acook3323]

Has anyone had a camshaft snap in half on them. My bike only has 6600 miles on it and it's broken! Is it possible for these to be defective?

[Triple Jim]

You just proved that it's possible. Sorry to hear about it, but unless you find something that caused it to lock up or something, it was just a defective part. I don't know your specifics, but it might be possible to get some help from Kawasaki.

[Motofool]

Originally Posted by acook3323

.........My bike only has 6600 miles on it and it's broken!.........

Pictures of the broken section?

[Z1R rider]

I suppose it could break if one or more of the cam bearing caps was loose. The bolts might have backed out and became loose or (like mine was) the previous owner had over torqued one of the cam cap bolts and broke it....then just left it and put the cam cover back on. Luckily I found it before anything else broke.

[acook3323]

camshaft.jpg

[acook3323]

I talked to a buddy of mine at a machine shop and he said by the looks of the break that it was most likely cracked during heat treatment and that it finally just gave out which is a lot better for me than a valve causing it to break

[dcj13]

Wow! That's really messed up

[Z1R rider]

@acook3323

was one of the cam caps loose or miss matched (reassembled in a none stock location) so that it had too much clearance or too tight at the bearing? I know, hard to tell what a PO might have done.

[acook3323]

I took the cam itself to a machine shop and they believe that it was a defective part that already had a crack in it and just gave out.

[Triple Jim]

You can usually tell if that's the case because part of the cracked surface looks different from the rest.

[Motofool]

Originally Posted by acook3323

I took the cam itself to a machine shop and they believe that it was a defective part that already had a crack in it and just gave out.

https://en.wikipedia.org/wiki/Fatigue_(material)

http://www.totalmateria.com/page.asp...ite=kts&NM=299

[Mohawk]

Yes that can happen from a manufacture or user damaage. Cams are very hard & made from a brittle material, so dropping them can cause cracks adjascent to where the profile changes or machining has taken place as those areas concentrate the shock loads.

Cam bearing caps if removed should always be put back on the shell half they came from, if not then the cam can set up a flex which can cause a shear in the same high stress points. But with such low mileage, I would hazard a guess that the part was defective.

Did it cause any other damage ? Valves, pistons etc ? If not you were lucky. I would approach Kawasaki, they may supply parts at cost as a good will gesture. But if not other damage was done, just get a second hand cam & off you go.

[Motofool]

Originally Posted by acook3323

I took the cam itself to a machine shop and they believe that it was a defective part that already had a crack in it and just gave out.

Reading your other related thread, I realized the following:
You should take any new camshaft and the cylinder head back to that shop.

Assuming the new camshaft is OK, if they find out that one or more of the journals are worn (the internal diameter/shape is greater than the specification's limit), you will suffer a similar failure again.

The reason is that the shaft should be supported by three journals, which support the cyclic bending forces produced by opening and closing the valves and by the rotating masses of the cams.
The material of the shaft is very hard to resist friction but very fragile to resist bending.

If the gap between journal and cam grows too big, proper lubrication does not happen anymore (the protective film cannot sustain itself); resulting a shaft that is scraping soft aluminum from the journal, making bigger in diameter and/or out of round.
Once that has happened, the shaft is supported and preventing from bending too much only by two journals.

Yes, the amount of deflection may be imperceptible, but fatigue (please, see above link) happens due to amount of deflection as much as due to number of cycles of deflections.
Any of those shafts can spin as much as 6000 times per minute or 100 times per second, when the tachometer is marking 12000 rpm.

[Petrolh34d]

Highly likely that it was cast defectively from the factory