Topic: 77 Cb550k Alternator rotor. Cracked and gouged with no apparent source?

[alacrity]

So here's a conundrum:  something HAD to have caused this.
BUT...
There are no loose pieces of metal inside the cover or around the stator or field coil.
I aimed a homemade dial gauge (pointer wire) on the rotor and rotated the engine and it spins round and true.
And yet, look at the crack on the inner ring and the nasty deep gouges on the outer surface.
The stator and field coil show no damage.

?

[calj737]

If you found no foreign material present, and the bike was running, the only plausible explanation is the damage occurred prior to your ownership and the offending material was removed, but the parts were not repaired.

[alacrity]

Yes, that's what I've deduced as well.
Thanks.
Now I need to find me some parts...
:-(

[alacrity]

and yes, it was running just fine. (a bit lean perhaps - but that's fixed now).

http://feelthemachine.tumblr.com/post/73901177054/77-cb550k-with-3mm-over-pistons-and-a-bump-in

[alacrity]

and while i have things open... I am doing some testing of the parts.
Weirdness from the rectifier.
 I performed the forward bias test using my craftsman 82141 multimeter in diode mode. red lead to green wire, black lead to each yellow wire.
I get what appears to be 600 ohms (give or take about 10) on each one.
Then I get the same numbers on the reverse bias test.

[alacrity]

I am hoping someone joins this conversation... 

I also have one of these from another project that I could concievably use. 
I performed the forward and reverse bias tests and guess what? Yep, very similar numbers to the OEM honda rectifier, and not what I was expecting at all from the FAQ step by step charging system inspection.
5-40 ohms on the forward method
+2000 ohms on the reverse method.

I'm right around an indicated 600 both ways?

http://www.colemanair.us/vp_asp/scripts/shopexd.asp?id=593
http://www.colemanair.us/Shared/RD_SeriesRectifier.PDF

[dave500]

its not cracked its how its made,its a butt joint.

[bryanj]

I seen a lot of rotors look like that where Numpties(engineering term) have tried to remove them the wrong way. Never seemed to matter they always charged ok as long as they spin true

[alacrity]

Dave500: I thought the same thing and as u looked closer. I saw an impact gouge on the leading edge of it that made me think it was busted. The last thing I would want is for this to detonate at 8k rpm


Sent from my iPhone using Tapatalk

[dave500]

dont worry about it,its not cracked,heres one of mine,i have four all the same,your gouge/impact mark might be a guillotine scar?

[rocco]

Hey,

I know this is late, but I just pulled my alternator rotor on a 78' CB550 and it has the exact same "crack" as this one. So I'm going to assume it's alright even though a mechanic told me he thought it was cracked.

[bryanj]

Don't use diode mode on your tester use the Ohms range and you should get the Honda numbers

[jonda500]

Hey,

I know this is late, but I just pulled my alternator rotor on a 78' CB550 and it has the exact same "crack" as this one. So I'm going to assume it's alright even though a mechanic told me he thought it was cracked.

Yes, it's fine, they all look like that!
John