Low compression, weighing options.

one thing I may have missed, did you hone the cyls, ? if so how did you do it,

Oval cylinder bores common?

I think so.

Five 750 four cylinder blocks, four were so oval they needed bored oversize, other one was oval also, but not so bad it couldn't be honed to size and still be within service limits.

I haven't checked any 1000 blocks, but it seems to me that the same thing would probably happen.

themachine wrote:

is it low compression? induce some pinging to seat the valves and rings........no.

just go flog the thing like theres no tommorow, if that doesnt seat the rings nothing will.

i thought i heard someone say 1075 kit?

After I put the bike back together, I took it out to a long, flat, country road and did a couple dozen cycles of WOT in 2nd gear up to 8500 RPMs then coast back to 2K and repeat.

Oh, and I have thought about the 1075 kit. Maybe someday.

BSKZ650 wrote:

one thing I may have missed, did you hone the cyls, ? if so how did you do it,

Yes, I did. When I took it to the machine shop to do the valves, I had them hone the cyls too.

With 43,000 on the motor the bores are too big now and no set of rins is going to make any compression, Your rings did seat. You were lucky to get 100lbs. Those clingers are Toast. Out of round, tapered, when u measured with the gauge it should have read HUGE!. A Vietnamese metal worker friend who's friends race motorcycles in Thailand asked me, "you know the Motorcycle"? He said: Take the peeston, put in hole, peeston fall through, no good! No pressure! Make peeston tight, grind peeston little bit. THey race 100cc 2 strokes. He sid my friends put together lot's of money thousands, bet on race, lose all the time. I come to united states, see the bigger peeston the suzuki, i call my country, tell my friend, he no believe me! I say i buy parts send them to you, you wait i come home, i put together, i give you money, you drive good. He say: Most time winna win by this much (spreads his arms apart) my friend he race the motorcycle, he win by 40 feet!! He say been 6yeea, my friends go all ova, they win 90% of time. He had yzf600 with carbs and pipes. Sounded MEAN. He weighed 100lbs tops. This person was very intelligent. Hed been everywhere and had done everything. we were working sheet metal on the front of a school and a spider skurried across one of the panels. I said theres a spider. He said "You know the spider? You eat him too"? Well that's where i draw the line. He showed me movies and videos about life in his country. One showed some kid cooking inside a homeless shelter, he was cracking a huge egg into a kettle of boiling water it looked like a fetus that came out of that egg. I looked at him and asked whatwasthat? He had a screwed up look on his face and said I don't know! So he didn't know it all. How bout another question on compression? :woohoo: :woohoo:

I would think economics would drive your anwer here...

How much does a set of rings cost? (the cheap ones, not the chromemoly)

How much does a set of geskets plus labor to install rings if you're wrong cost?

I would think you would be better odds to get the rings.

One major factor in my reasoning is this... You said you do think you oiled the pistons when you assembled, so you have at least decent odds that your current problem may be glazed cylinders, and rings. so those rings may not seat in the new cylinders either.

Another is you suspect oval cylinders may be your problem, so that could give you uneven wear on your rings. (sure it's not much, but your putting a good bit of money on the other side of the combustion chamber, why not make the rings right too.)

As a side note, it is very common for cylinders to be
SLIGHTLY oval when they are COLD! That's one of the reasons your engine has out of round specs.

Theoretically as the engine warms up, the cylinders become more round and the compression goes up. Which leads to a new question... did you check compression both cold and at normal running temp and are they the same?

I would think you might still have a chance at getting your rings to seat, if that is indeed your problem.
Some ideas I've seen kicked around to get a booger set to seat,

1. pull the plugs, wash down the cylinders with B12, replace the oil with mineral oil, or alternatively, crank the cylinders over for 15-20 seconds dry. Drive as usual.

2 run transmission fluid in a tank of gas. ( will barely run and will smoke like a freight train) This has also been used as a cleaning method for cabon buildup on valves.

I've tried no 1 with limited success. never tried no 2 for that.

good luck and best wishes.

nads.com wrote:

With 43,000 on the motor the bores are too big now and no set of rins is going to make any compression, Your rings did seat. You were lucky to get 100lbs. Those clingers are Toast. Out of round, tapered, when u measured with the gauge it should have read HUGE!.
(SNIP)
How bout another question on compression? :woohoo: :woohoo:

Wow! If understand this correctly. You're saying an engine is toast at 40k miles? Holy shit Batman! :pinch:

This is interesting because the person that started this thread mentioned he had a machine shop hone the bores...
I wonder why they didn't mentioned "oh by the way... yer gunna need a new set of pistons and rings cause we just chewed x thousands off the walls to get'em back to cylindrical from their ovaled-out shape!"?

Is this something common to that model or do all KZ's suffer from this sort of short engine life expectancy?

wrenchmonkey wrote:

nads.com wrote:

With 43,000 on the motor the bores are too big now and no set of rins is going to make any compression, Your rings did seat. You were lucky to get 100lbs. Those clingers are Toast. Out of round, tapered, when u measured with the gauge it should have read HUGE!.
(SNIP)
How bout another question on compression? :woohoo: :woohoo:

Wow! If understand this correctly. You're saying an engine is toast at 40k miles? Holy shit Batman! :pinch:

This is interesting because the person that started this thread mentioned he had a machine shop hone the bores...
I wonder why they didn't mentioned "oh by the way... yer gunna need a new set of pistons and rings cause we just chewed x thousands off the walls to get'em back to cylindrical from their ovaled-out shape!"?

Is this something common to that model or do all KZ's suffer from this sort of short engine life expectancy?

Most KZ's never see those kind of miles (except Ron's) because they are run hard. look on ebay and you will see the average mileage of a 25-30 year bike is around 25K. But that is a hard 25k, at least on my bike it is.

If the machine shop honed them and then the new rings were inserted and measured to be in spec, there is absolutely no way there was an unacceptable amount of wear on the cylinders, though. We could debate how long cylinders SHOULD last till the cows come home, but the rings just don't lie.

my bad. sounds like the rings never seated. Id ask what grit they honed them with to make sure it's correct for the rings though. I've got 400,000 on my old kz and shes running strong. Course it,s time to take another pill, did I take the green one? Or the yellow one? Well ill take two then.:sick:

how about that head gasket? did you re tourque the head, and is there a chance in hell it could be leaking equally on all 4 cyls :huh:

Thinking "honing" is simply de-glazing cylinder walls so new rings can seat. And that boring (not honing) is needed to bring an oval cylinder to specs. Could result in a "de-glazed" oval bore.

Perhaps the machine shop was engaged to do a valve job and to de-glaze the cylinder walls with a honing brush, but not requested to measure the bores or test fitment of pistons or rings.

Is re-sleeving not a feasible option?