Plain Bearing Crank Bearing Wear

[Nessism]

First photo shows the worst three bearings. KZ750E

Second photo shows the others.

There is a nick in one of the bearings that concerns me, but otherwise the shiny marks don't seem to have suffered significant material loss.

What say ye? Replace or run?

[Sci85]

There's definitely a difference in wear on the top three. I wonder why they would wear differently? Is there anything common amongst the top ones? I'd replace them all just because I had the cases open so why not? Are they expensive or difficult to find now? I guess you could also clean them up if they still measured in spec.

[rphillips]

Jerry Clower once said, if you have to ask yourself, should I do that? Don't do it. Ask yourself, do I want to use those old bearings. Just my opinion

[tatu]

It's open, put new. If they were mad cost or hard to find you could put those back, I might even be tempted to put the best pair where the worst ones were to even it all out if you like. I've not done it and first option would always put new even if it were just disturbed. Some engines specify new rod nuts or and bolts as well.

[Nessism]

Thanks for the comments guys.

I've decided to replace the one bearing shell with the gouge and run the rest. Each shell half costs about $9 so that's $90. If they were worn more I'd be concern, but they really aren't. Just some light scuffing.

[Sci85]

Hey Ed,

Here's the bottom pieces of the bearings out of my '90 ZX-10 engine. I was wondering the same thing since I'm only familiar with engines running roller bearings like the GS's. They don't look that bad to me but it's obvious there is some wear.

Any comments from folks who have built plain bearing engines? What say you folks?

[trippivot]

clean up the surfaces - smooth the nick out - Take a plasti-gauge measurement - then you can make a decision how much material is left.

[GregT]

The 750 shells look fine to me, The early family of Kawa 4's 550/650/750 have a much better lubrication system than the later 16V 900/1000/1100.
Both suffer from kawasaki's habit of using one main to feed two big ends though.
The 16V motors like your ZX10 usually show problems on the rod bearings first, so pull the rods while you've got the crank out.
Given that one of the mains is fed by a small diameter bent tube - and this is supposed to feed two big ends as well, it's worth keeping good oil in it.
The pitting on one shell indicates condensation has occurred - probably due to long periods sitting. If you see that, check the oil pressure relief valve as it's a low point in the system and I've seen corrosion damage in them.

[Sci85]

Wow thanks guys! I posted almost the same thread over on two kawasaki/ninja forums and got squat for replies. I don't know why I even bother with any other forum site.

Yeah, this is the second Kawi I've been into and I can't say I'm that impressed with what I've seen especially compared to the Suzi and Honda's I've done.

I'll check the relief valve for sure.

I heard about the rods but am reluctant to pull them apart because the factory service manual says to use new bolts each time an that's 128.00 bucks just for freaking bolts! WTH??

[blowerbike]

#3 spun bearing has been a common problem on the earlier big ninja's for years.
terry kizer offers a pan mod to fix this before it happens.
redirects oil to the #3 rod and keeps it happy.

[GregT]

Wow thanks guys! I posted almost the same thread over on two kawasaki/ninja forums and got squat for replies. I don't know why I even bother with any other forum site.

Yeah, this is the second Kawi I've been into and I can't say I'm that impressed with what I've seen especially compared to the Suzi and Honda's I've done.

I'll check the relief valve for sure.

I heard about the rods but am reluctant to pull them apart because the factory service manual says to use new bolts each time an that's 128.00 bucks just for freaking bolts! WTH??

The ZZR11 went to bigger rod bolts which are better, but for road use I wouldn't hesitate to reuse the originals. Use loctite too...

The 500 twin uses the same rod bolts and we used to reuse them twice before replacement - and we ran them to 13000RPM...

[Sci85]

#3 spun bearing has been a common problem on the earlier big ninja's for years.
terry kizer offers a pan mod to fix this before it happens.
redirects oil to the #3 rod and keeps it happy.

Ok cool. I'll check him out. Thanks blowerbike. If they knew they had a problem, why didn't they recall and fix the obvious design flaw? What a croc.

The ZZR11 went to bigger rod bolts which are better, but for road use I wouldn't hesitate to reuse the originals. Use loctite too...

The 500 twin uses the same rod bolts and we used to reuse them twice before replacement - and we ran them to 13000RPM...

Ok whew! Thanks for the info GregT. That saves me some real money. Are all plain bearing motors like this? I mean, sheez talk about an expensive rebuild. Bearings and bolts alone are almost 300 bucks. Are plain bearings that much better than rollers that people are willing to spend that kind of money? I can't imagine what it must cost to drag race one of these engines...

[GregT]

Ok cool. I'll check him out. Thanks blowerbike. If they knew they had a problem, why didn't they recall and fix the obvious design flaw? What a croc.
Ok whew! Thanks for the info GregT. That saves me some real money. Are all plain bearing motors like this? I mean, sheez talk about an expensive rebuild. Bearings and bolts alone are almost 300 bucks. Are plain bearings that much better than rollers that people are willing to spend that kind of money? I can't imagine what it must cost to drag race one of these engines...

Kawasaki's of this generation - 16V 900/1000/1100 all have the bolt in bearing block and the pipe feeding it. Bad design.
The 1200 onward doesn't have the bolt in block but still feeds 2 big ends from one main...They also have a crank with a surface treatment such that when a bearing spins, the crank cracks.

Most plain bearing motors are way better than these...

[Sci85]

Most plain bearing motors are way better than these...

That's good to know. Like I said earlier, I'm not impressed with the Kawi engines at all. The first one I did was roller bearing design but even that engine was oddball compared to the Suzi. I'll get this one back together and sell it off and that will be my last Kawasucky...