Copper filings on oil filter base.

These guys would know for sure, as they have done a lot of the older 4's.
Hope you can fix it and still make the trip, hate to plan for a year and not go!!

If there is no odd noise and the oil light is staying off I would ride it and flush the oil....

Maybe it was the remains of a previous engine problem, maybe the neighbor kid put a penny in your oil fill... who knows but if there is no problem then hey, there is no problem!

I agree with wireman for once!

Galactica wrote:

I'll look around myself this evening (right now I'm committed to some time with my wife), but are you guys sure the big end bearings are rollers?

Absolutely certain they are roller bearings.

110% certain they are roller bearings on a pressed crank.

Thanks for all the info. I'm doing a 600km (400mi) camping trip on it this weekend to shake down my gear. I'll pack as for the 3000mi trip. Assuming all goes well, I'll dump the oil and drop the pan next week. I actually don't expect to find a problem, but you never know.

It's an interesting issue though. I'll post my findings and pics next week.

hardr0ck68 wrote:

If there is no odd noise and the oil light is staying off I would ride it and flush the oil....

Maybe it was the remains of a previous engine problem, maybe the neighbor kid put a penny in your oil fill... who knows but if there is no problem then hey, there is no problem!

I agree with wireman for once!

dont ruin your perfect record on my account :S

PLUMMEN wrote:

hardr0ck68 wrote:

If there is no odd noise and the oil light is staying off I would ride it and flush the oil....

Maybe it was the remains of a previous engine problem, maybe the neighbor kid put a penny in your oil fill... who knows but if there is no problem then hey, there is no problem!

I agree with wireman for once!

dont ruin your perfect record on my account :S

Hey even a broken clock is correct twice a day right?

otakar wrote:

110% certain they are roller bearings on a pressed crank.

Why arent cranks made with babbit bearings and pressed together parts? The you could replace damaged journals and youd have the high rpm sometimes sought after.

nads.com wrote:

otakar wrote:

110% certain they are roller bearings on a pressed crank.

Why arent cranks made with babbit bearings and pressed together parts? The you could replace damaged journals and youd have the high rpm sometimes sought after.

nads, I think that you have to look at it as an engineered system. First, in 1975, 10,000rpm was pretty hot. Second, it's not just the main bearings are not the only limiting factor on the redline. Two valve heads can't breath very well at the top end, and still be streetable. Even if you do use huge valves to breath up top, then you have to run high valve spring pressure to control the valve float. This is hard on camshafts and timing components like cam chains etc. Mother Kaw had to make a decision about performance/durability and in the 1970's they definantely erred on the side of durability. It's the whole reason that we laud the KZ for being reliable, and still ride 30 year old bikes all over the country to this day. If you want a motor that you can rev to the moon, then go get any newer 600 cc sportbike. Most of them redline around 17,000 rpm and make more hp than your KZ, and come with a warranty. Will they last 30 yrs? Not likely.

Unless I missed something in these post, what about the bronze bushings in the connecting rod at the wrist pin and piston?

like someone said; dump the new oil and look for more metal shavings. do it again if necessary. a coating of used oil can make steel fragments look like brass. you need to take a magnet to them.

how many miles are on your engine?

how often do you change the oil?

i think you are worrying too much.

Hard to say how many miles on the engine. The odometer read 8900 miles when I got it, but the motor is kinda tired. Compression is 115-135. I've put about 14000 km on it (about 8700 mi), and I change the oil about every 3000-5000 km ( about 2000-3000mi).

I just got back form a 600km (400mi) ride. Just waiting for it to cool down, then I'll drain the oil and have look.

She ran flawlessly until I pulled into the garage and I saw fuel pissing out of the #3 carb overflow. I quickly shut off the petcock, drained the bowls, removed the #3 bowl (damn it was hot), flicked the float a coupla times, reassembled, and voila problem solved