KZ650 Rod & Main Bearing Source?

I'v pulled all 5 of the upper half bearings and cannot find a hint of colored paint anywhere, which is frustrating because it seems bearings are sold by color and not size. Partzilla only has brown main bearings listed. I'd place the order today if I was certain they were correct but its a lot of money to gamble on a 1 in 3 chance.

I suppose these markings don't mean anything, or do they?

There's a KZRider member named Larry Cavanaugh. He owns Cavanaugh Racing, and he has a very extensive knowledge about the KZ bikes. Before you buy new bearings you may want to contact him either through this site (his ID is LarryC) or at his business (link below). He hasn't logged onto this site since January 23, 2018, so it might be best to try contacting him at his business. Ed

www.cavanaughracing.com/

You can still buy the three main colors/sizes. All you have to do is order the bearings for a 1980 kz650 or any kz750 as they all use the exact same bearings.
www.partzilla.com/catalog/kawasaki/motor...-kz650-e1/crankshaft
They DID change bearing materials in 1983 and then gave them new part numbers. Years ago when I was ordering new bearings, the 1981 kz750 ones were $22 bucks a piece (thats for one half bearing shell which is $44 total for one journal) and the 1984 gpz750 ones were $9. So guess which ones I bought?
They have since combined all the bearings and lowered the price. Just like when you order a composite base gasket for a gpz/kz750, they will send you the metal base gasket for the zr-7.

Here is how the main bearing/ are marked on the crank and case and then cross referenced to determine the correct color. But please refer to a service manual for complete instructions. There are also connecting rod bearing markings on the crank but use different color codes, so don't don't get them confused. Again...refer to the manual.

Looks like my crankshaft has no markings and my case has no markings. This would mean I would need the "Blue" main bearings (1.498mm - 1.502mm), or, (.0589" - .0591") in bearing thickness. Unfortunately I don't have a quality metric caliper. My inch caliper only reads to the thousandths place, and the difference between the bearings available is 2/10,000". Because my existing bearings are worn I have to take an average reading, and that is a bit over .058" to .059". It is not possible to measure that accurately with the tools I have on hand. I've got a Starrett 0-1" micrometer but that also only reads to the nearest 1/1,000", plus, it has a flat anvil which is no good on the curved bearing surface. Probably the closest I can come will be to use Plastigauge, but I have to wonder how accurate that will be given the uneven wear on my current main bearings. Plus, that will only tell me the clearance between the crankshaft and bearing, not the actual thickness of the bearing.

Use a ball bearing & your micrometer and deduct the diameter of the ball bearing to get the bearing thickness?

Warren3200gt wrote: Use a ball bearing & your micrometer and deduct the diameter of the ball bearing to get the bearing thickness?

Great idea!

A micrometer should have a Vernier gauge that gets you 1/10,000 th of an inch. Look at the thimble, you can see marks for the Vernier.

How to read .0001" on a micrometer:
www.chicagobrand.com/help/micrometers.html

loudhvx wrote: A micrometer should have a Vernier gauge that gets you 1/10,000 th of an inch. Look at the thimble, you can see marks for the Vernier.

How to read .0001" on a micrometer:
www.chicagobrand.com/help/micrometers.html

Mine doesn't have the Vernier scale; it only reads to .001", but I can closely estimate the remaining .0001" between the graduations.

For example, the reading here is .1135" (line is halfway between the 13 & 14).


Using a ball bearing as was suggested by another poster I measured each upper main bearing shell in 3 places. Next I subtracted the ball bearing diameter and averaged them together for an actual bearing thickness.

The results were: #1 = .0584", #2 = .0583", #3 = .0586", #4 = .0582", and #5 = .0583"
In metric the upper bearings are #1= 1.4833mm, #2= 1.4802mm, #3= 1.4884mm, #4= 1.4782mm, #5= 1.4808mm
These are all slightly below the smallest "Brown" bearing thickness range, which is 1.490mm - 1.494mm. I suspect this is due to wear. If the lack of markings on crankshaft and cases are an indicator, the engine should require the "Blue" bearings which would be 1.498mm - 1.502mm.

I think I'm going to get some Plastigauge and measure the actual oil clearance, then I'll pull the crankshaft and measure the actual journal diameter.

Ok, sorry. I don't think I've ever come across a micrometer without a Vernier.

Been carefully measuring the internals of this engine. Last night I measured the crankshaft journals. The good news is the main bearing journals look to be within specification. Tonight I picked up some Plastigauge on the way home from work and measured the oil clearance on the main journals. Three of the five are within spec and the other two are just outside of specification, but on the tight side, not the loose side. My original theory was the bearings didn't measure (thickness-wise) within tolerance because they are obviously worn, but now it looks like they are just the right size. Well, that would be no problem except that the thinnest bearings (the "brown" ones; sized 1.488-1.493mm). My fear is if I buy the thinnest bearings they will still be thicker than the ones I have, and would therefore have less oil clearance than I have now, which is on the tight side of the tolerance. To further complicate matters, the chart says my engine is supposed to have the "blue" bearings, which are the thickest of all. Nothing seems to add up here. Any idea where I've gone wrong?

Plastigauge measurements look good to me:


The measurements

In an earlier post you mentioned measuring the bearing shells in three places and then (presumably) averaging. I think it would be better to take the thickest of your readings because that would show the least wear condition.

Just a thought, you did use a new ball bearing which is perfectly spherical and not an old worn one? If you measured an old one in several places it would be a different reading and skew your calcs.