TOPIC:

I've got the engine out of my '79 on the bench and torn apart for inspection and overhaul. I'd like to replace the crankshaft and rod bearings when I reassemble it but I have't had luck finding them. Any idea where a man might find new stock size bearings?

Be aware that there are at least 3 different sizes of the connecting rod bearings, and installing the wrong size may lead to problems. Take a look at item #14 in the link below for more info. Ed

shop.gearhead.com/oempartfinder.htm?arib...50-C1-1977/070052B-7

www.ebay.co.uk/p/Kawasaki-NOS-Big-End-Be...z650-Kz750/645465816
B1 to B3 parts list says this part no which is different to ebay lsting. Beware 92028-1102

650ed wrote: Be aware that there are at least 3 different sizes of the connecting rod bearings, and installing the wrong size may lead to problems. Take a look at item #14 in the link below for more info. Ed

shop.gearhead.com/oempartfinder.htm?arib...50-C1-1977/070052B-7

So if I understand this I'll need to remove the rod bearings and look for a color marking? Also, based on that link is it safe to say there is only one main bearing size (color) or do I need to be mindful of variations there as well?

First you shoul determine for certain that new bearings are needed. These engines are surprisingly robust. Unless the engine spent its whole life at the dragstrip, or has 200,000 miles on it, or was seriously flogged without any oil, the bearings are probably ok.

TexasKZ makes an excellent point. My 1977 KZ650 has more than 61,000 miles on it and there are no bearing problems. Of course, my bike is still in it's infancy. RonKZ650 put more than 168,000 miles on one of his KZ650 bikes (see link below) and I don't think he experienced any problems with the bearings. Is there something in particular that leads you to believe the bearings are bad? Ed

www.kzrider.com/forum/5-chassis/603552-r...heavy-braking#746917

Here are some pics of the some main bearing halves. Now I have not checked them with Plastigauge so my thoughts on replacing them are only based on look and feel. Mostly I thought it might be a good idea to install new bearings since I'm into it this far. Thanks for the help and advice.

There are raised bumps on several of the upper halves. I haven't yet removed the crank to check the lower halves. It's difficult to capture on camera but the dark round raised spots can be felt with the finger.




The crank journals look pretty good though.

After seeing them forget the plasticgage idea (you know about that anyway) and see what others think....... look a little rough to me.

That is really interesting. I cannot imagine how the bearings would get bumps. I think you will want to plastigauge them anyway. As I recall, the color coding has to do with the thickness of the bearings. Are the crank journals ok?

There are a series of specific stamps/marks on both the crank itself, and the lower engine case that Kawasaki used to determine what bearing shells to use to obtain the correct clearance. When the case was line bored at the factory they measured it and stamped the case to signify the inner diameter. The crank journals were also measured and marked according to the size. You then compare the crank and case markings to determine whether to use blue, black or brown coded bearings. Your old bearings will probably still have the color code marks on the side. (Mine did at least.) You can then verify that they match the case/crank markings to better help you order the correct size.
Once you have the new bearings installed you can then plastigauge the journals to verify that the proper clearance has been obtained.
This will all be outlined in the factory manual.

I bought all my crank and connecting rod bearings from Partzilla.com

MkC wrote: So if I understand this I'll need to remove the rod bearings and look for a color marking? Also, based on that link is it safe to say there is only one main bearing size (color) or do I need to be mindful of variations there as well?

Sizes in both main and big end shells will most likely vary , it's rare (but possible) for them to be the same.
Simply go by the colour markings on the edge of the shells for re-ordering replacements and if the paint is no longer visible then use the number system on the upper case and crankshaft..
The raised dimples are common and i have seen it plenty on the camshafts shells of the bigger Z900/1000.
I think it's either heat/lack of lubrication or batch related and tend avoid re-using them.
Looking at your pics there is also evidence of light scoring and i would fit new shells and be sure to use a quality oil when re-built.

Most likely the bearing shell color code will still be visible. You may want to try removing a shell or two (don't forget where they go) and looking on the edge of the shell for a paint mark. As mentioned, they are either blue, brown, or black. Then simply replace the shell with one of the same color.