Topic: Crank Wear?

[MidnightLamp]

 

So both of my bits-bike engines have been opened up for my new build, and I'm looking at both cranks and am less than happy with them. The damage is one tiny burnished spot, and some odd scaling. I can't even feel it with my nail or the surface of my fingers at all. Have attached pictures below.

One is from a spare F2 engine,
http://i53.tinypic.com/4t1opv.jpg
http://i54.tinypic.com/2qxbzo3.jpg
http://i51.tinypic.com/2ypg6fr.jpg
http://i56.tinypic.com/29fwbjd.jpg
http://i54.tinypic.com/28nz94.jpg

The one below is from a K5. In the pictures, you can also see the bearings, one or two of which has some light gouging?! The damage is mainly the grooving, but also the difference in surface from the babbit face to the oil face of the crank journal. Where did this damage come from??! 

http://i56.tinypic.com/1ghdp0.jpg
http://i51.tinypic.com/2mw9u8p.jpg
http://i53.tinypic.com/91c4ea.jpg
http://i52.tinypic.com/30artiq.jpg
http://i54.tinypic.com/110bryp.jpg

I have no history on these bikes, but I was hoping to run the F2 crank. Are the journals on both of these toast, or can a little polish go a long way?

Any help you guys can throw my way will be much appreciated!

Cheers!

[scunny]

imho that F2 crank is good to go, the K5 looks toast. but don't trust me, I'm cheap.

[camelman]

That bearing looks a little worn, but I imagine they'd work.  Replacing would definitely ease the mind though.

I took a 1 mm deep gouge about 10 mm long and 4 mm wide out of the crank on my first car (1983 Honda Accord), and drove it another 20k miles before I sold it.  It ran like a top. 

Camelman

[dave500]

if you cant feel the marks its ok.they look good to me.normal wear.

[City Boy]

Hi Midnight.I have viewed your pics and I do not see any unusual wear and tear.My next move would be to polish the journals and crankpins and then install and plastiguage fitted bearings.New bearings would be ideal although if cost is an issue I have also had reliable results from using used bearings including mixing individual shells from different engines!   Rock On

[Legin]

Polish and new shells then good to go. Some evidence of dirt so a good oil way clean as well.

[MidnightLamp]

Thanks for the feedback guys, just dropped off the F2 crank at the machinist! 

My only concern was getting into the mess that is buying a used "good" crank, because as I see it I'd be going through a lot of ebay and forum cranks based on someone else's interpretations of what "good looking journals" means 

I'll be popping it in with new shells of course. The K5 crank will be retired, but I want to try converting it to grub screw oil bores for practice.

Cheers and thanks!

[bryanj]

I rekon the K5 is better than the F2 and all those marks are oil/filter not changed often enough and/or incorrect grade. plus if been apart before not clean enough on re-build