Crank Journals?

I am working on a GPZ750 engine and finally got the cases apart and had a question about the crank journals. I took as good a picture as I could get and here is what I have. My question is if these have a problem or if they are good enough to reuse. The spots on the one journal made me wonder and the way the hole around the crank oil passage looked like it had been ground a little (may have been before the crank was installed. Any ideas on if these are still good or do I need to start investing in journals and some crank work?

Crank shaft.

yeah shes had some dirty oil in the past.the easiest test i know of to check to see if a crank needs help is to rub the edge of a penny across the journal,if it picks up copper off the penny it needs some help.do you have any better pictures?

You can also check and verify the crank journal oil clearance using plasticguage, its like a wax piece of string you put on the journals and torque everything down, without turning the crank. remove the journal caps and you should be able to see and measurre the thickness of the wax strip after it has been crushed. also see if it is tapered.

I'll try for some better pictures today. The flash was reflecting and washing out the pictures. I was going to borrow a micrometer from a friend and check for roundness. I've got to do the same on the rods to make sure the piston pins haven't worn the rods. They had some dark areas from oil.

I'm worried that the cost of fixing it all may out do the benefits of the larger bore. That and if I send the crank in for work it is tempting to have lots of work done, and that leads to lots of other work and then an engine that costs more than the rest of my bike. Really I am hoping to put this one back together for the cost of wrist pins, gaskets, rings, cylinder honing, valve guides, seals, and a few other things. Otherwise it is going to be a 2 year engine build. However, I don't want to put it together once to have to tear it down in 6 months to do it right.

I don't have any history on the engine, other than when I picked it up it would not turn over, however, a little extra torque on the bolt on the right end of the crank and it popped free and turned over. My guess is a stuck ring as I didn't see any scratches on the crank. Compression was about 40-50 across all 4. Thats all the background I have on it.

Kawi,My eyes aren't what they were, but pic's look like plain bearings are just showing babbit material.would inspect big end rod bearings.if ok, would try this. Get some 600 or finer garnet stap, break (soak) in solvent, and polish crank journals lightly, replace bearing shells w/new (stock if options are avalible(on some bikes there are no opts)and plastiguage. if plastiguage is within + 10% loose, of spec. run it. worn main bearings lose oil presure, which as a result leads to greater wear at rod big end bearings. In a perfect world plain bearings see no contact and should never wear. unfortunalty mostly due to lack of oil cushion at at startup/low oil pressure /passing of debris, wear does occur. passing graft leaves linear striations on crank journal, low oil pressure polishes (eggs) journal at thrust angle. I don't see obvious signs of these. luck G

Send us the crank, we will check it out and if it is OK, we will micro polish it and send it back.
aperaceparts.com/mailers/crankmail.html

Jay

I may drop it off next time I'm passing through to Lancaster. Downfall is saying no when you offer to lighten and balance it as well .

Here are some better pictures.

Another.

And a rod end.

Looks OK to me. Those grind marks next to the oil hole is something Kawasaki does.

Jay