A bit baffled by shell bearings

Hi

Any thoughts would be welcome.

Of necessity, I've had to open the engine on my KZ440. While it's open, I'm renewing things that need to be renewed, as well as things that don't get a look-in unless the engine is open. For example, cam chain. Obviously, crank seals as well. But now I'm thinking, shell bearings... My conrods are well within the allowed spec for side clearance. They're fine. So it's generally undesired to remove them at all and disturb the OK bearings in them. But I have to replace my pistons anyway, shell bearings are cheap, and so the conrods have to come off...

So I looked at the manual, and the information is confusing. Apparently the shell bearings you need are not just one part number. There are 4 different part numbers corresponding to markings on the conrods AND crankshaft. Surely, this can't be right? The book says, it depends on whether the conrod and crank are black or brown, and whether each have an "O" marked cast in relief, or they don't. I don't know. There's also a table underneath which says bearing insert thickness varies according to which colour it is: blue, black or brown. Ah, it's confusing.

In any case, I was thinking, on the one hand, if I find it confusing then so would others, in which case those bearing inserts have never been changed. On the other hand, the bearings already in there are fine. Should I persist and replace them anyway? I'm worried I'll make a mistake and choose the wrong bearing inserts.

I kinda went through this. I rebuilt a kz440 a couple years ago. The guy I got it from had the external oil line break and he ran the engine low on oil and destroyed the con rod bearings. I remember there was 3 or 4 options depending on the paint mark or some color of the crank. It was a royal pain in the ass. 

What are the condition of the bearings?  Unless they are all scuffed up, there is no value in replacing them.  If they are scuffed, first thing is to look for the color on the bearing edge.  Most likely it will be easily visible, then order the same color.  If the color is not obvious, use the FACTORY Kawasaki manual, and work though the details regarding what bearings you need.  It ain't that hard to figure out.  What is hard sometimes, is finding the proper parts for your bike.  A quick check at partzilla suggests that Kawasaki doesn't sell con rod bearings anymore.  That leaves ebay.  Hopefully you can find what you need.

If they are within spec I wouldn't unbolt or change them. You can change the pistons by removing the barrels.
Steve

I wouldn’t change any bearings if they don’t need to be. 

What is the reason for replacing the pistons ?
When it comes to "big end" shells side to side movement won't tell you their condition. You can only inspect them by removing the caps (make sure they go back in the same place and the same way round) as long as the bearing is seated correctly and lubed when you put it back you should be fine (don't lube the back of the bearing) For the small cost and time involved I would measure the bearing clearance with plasigauge for peace of mind now you have gone to the trouble of getting in there.

Wookie58 wrote:

What is the reason for replacing the pistons ?
When it comes to "big end" shells side to side movement won't tell you their condition. You can only inspect them by removing the caps (make sure they go back in the same place and the same way round) as long as the bearing is seated correctly and lubed when you put it back you should be fine (don't lube the back of the bearing) For the small cost and time involved I would measure the bearing clearance with plasigauge for peace of mind now you have gone to the trouble of getting in there.

Replacing the pistons is absolutely necessary because one of them blew up (disintegrated), as per a previous post.

The manual states that sideways clearance should be measured from the big end (i.e. slip a plastigauge between the conrod and the edge of the crank) as you've stated, and specifies a wear limit for this. I have no reason to suspect anything is wrong with the bearings. I will probably not replace them.

As per the other poster, I would find it tricky to install the pistons while the conrods are still attached to the crankshaft.