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I think you misunderstood me. The total movement of the crank is way more than 0.025". It is closer to 0.125"

But thanks, I think you are correct about roller bearings, at least that is the way I remember it. They do look to wide to be ball bearings unless they are double-row ball bearings.
Hmmm, If the bearings are roller or ball, the races would be steel? Wouldn't that mean the play is from the dowel wobbling in the case... or missing?
 

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Roller bearings, wow! in 1984, did Kawasaki have a few thousand bearings leftover from the 500 and 750 2 stroke engines?

I thought by then they would all have automotive type soft alloy split bearings.
Anyway, the bolt of the rotor should pull the crank against the thrust surface in the crankcase, but this engine has pinned roller bearings;
I wish I had one in front of me because it's tough to see how it works in any of the parts diagrams, or pictures of parts on Ebay.

Doesn't someone else have one of the older engines apart right now?
 

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Discussion Starter · #26 ·
Roller bearings, wow! in 1984, did Kawasaki have a few thousand bearings leftover from the 500 and 750 2 stroke engines?

I thought by then they would all have automotive type soft alloy split bearings.
Anyway, the bolt of the rotor should pull the crank against the thrust surface in the crankcase, but this engine has pinned roller bearings;
I wish I had one in front of me because it's tough to see how it works in any of the parts diagrams, or pictures of parts on Ebay.

Doesn't someone else have one of the older engines apart right now?
Ha-ha, nope. They would have needed far more than a few thousand bearings. When Kawi designed the very first 4 cylinder 4 stroke in 1970-1973 (the Z1) they decided to go with rolling element crank bearings and break with tradition. By doing so, they could use very low oil pressures and get very low engine friction. The low oil pressure meant far less chance of oil leaks and the engines proved to be super reliable.

I think Kawi stuck with this design for the entire KZ 4-cylinder series of bikes. I see the new Z900 has plain bearings however.

Yes, ideally I would love to hear from someone who has one apart now, or has a crank kicking around that they could photograph.
 

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Third edit. While I concur with Kawasakian yeah it is a nagging mystery. These air cooled Kaw big fours were extensively raced and modified for decades, there has to be a guru corner or machine shop that still operates that can help identify the issue and give a concrete answer on what is the cause and should it be addressed and cost involved. That said I looked on the web but came up empty, maybe someone else can have better results.
 

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Discussion Starter · #32 ·
Technically we are not supposed to direct members to a competing web site. But anyone is free to use google which is what I did and came across the same link as haybaler posted. It is somewhat helpful, but I am pretty certain my crank has not twisted which is mainly what that thread is about.

A this point I am torn between three options:

1) Run her until it explodes. (maybe this will never happen)
2) Part it out.
3) Split the cases to find and maybe repair the cause.
 

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I think that bike would all of a sudden start to vibrate a real lot, and you would know to shut it down. Of course, you could just ride it without leaning, on straight roads. :p

Are those crankshafts pressed together?
 

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Discussion Starter · #34 ·
Yes they are pressed together at the factory with tons of force. But I have heard that when you put an aftermarket turbo or supercharger on these engines, you better weld the crank first, or you may end up twisting it.
 

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Same thing with the early GS1100 Suzuki's. I think the 1150's are one piece forged. I never liked the idea of pressed cranks. It seems to me if they are going to do that, then weld them up, make them flat plane and reap all the benefits. Ah, what do I know. I wake up and go to sleep everyday with the realization that I haven't a clue as to what's going on. I'll probably utter my last breath and waft out a hissing, "What was that all about?". 馃
 

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$89 buck is more than reasonable. I won't even take my Tig welder out for that much. Redoing the whole crank for $1K , that is a "gulp" for sure. Doesn't it seem that the only thing that would allow that crank to move like that would be an outer bearing, or one end of the pressed crankshaft having lost it's location? Also, wouldn't it have to be the one on the opposite side? If the number 5 bearing lost the pin, then the movement would be either the end bearing(s) have moved. The crankshaft spreading might cause that end to come out, but the movement in and out is really weird. The connecting rods would not allow that kind of movement, the only thing left is a problem with the outer pressing of the crankshaft ends, and without seeing one in the crankcase, I don't know how you could check these parts without a tear down. The rods would bend with that kind of play, methinks. I think the crankshaft is being held in place, but one of the crankshaft ends has done something that defies physics. :)
 

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Since the motorcycle piston pin is free floating in the con rod small end the rods are sufficiently free laterally to allow crankshaft movement of a few mm.
Pic from
shows the total gap between piston boss and rod.
Stonemason's hammer Kitchen utensil Steering wheel Gas Auto part
 

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Discussion Starter · #40 ·
I am surprised that so far, nobody has claimed to have split the cases of any Kawasaki 4 cylinder engine that uses roller bearings. This would include the Z1, KZ900, KZ1000, KZ1100, ZN1100 and the police versions. Perhaps that is a testament to their reliability?

To answer Kawasakian's question regarding how crank end float is controlled and to comment on his theory, I did some digging and found this photo of a KZ900 crank for sale on fleabay.

Note that in the photo, the outer bearing races are totally free to slide back and forth by a very large amount. These bearing races will be somewhat retained from axial movement once they mate with their corresponding set pins that are in the crankcase bearing bores. However, I believe the main function of the set pins is to make sure that the oil hole in the outer race, stays lined up with the oil feed hole that is in the crankcase. Since that hole is generously oversize, the set pins do not have to be a tight fit.

However we do know that bearing #5 is designed to fix the crank to the crankcase to prevent axial movement. So all thermal expansion will move outwards from bearing #5. This outward movement is easily permitted by the free floating design of the outer races of the rest of the bearings. Thermal expansion would be in the order of only a few thousandths of an inch, so where did 1/8" of float come from?

My current theory is that the tiny pin that locks #5 bearing to the case has sheared or was omitted by whoever may have split the cases in the past. Without that pin, the crank is free to move quite easily based on what I see in the drawing below. Bearing #5 is the one right next to the large gear on the RH end of the crank. Comments?

Auto part Machine Nickel Bicycle part Titanium
 
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