so what is the real redline for these kz1000 or 900

So what is the real redline for these kz1000 or 900?

Depends on how bad you want to keep riding it. Take it up to 12k if you plan on doing a rebuild soon. :laugh:

Get an accurate tach, even mounted temporarily, and carefully work your way up on your shift points, or better yet, use a rev-limiter you can adjust; start low and work your way up. If your bike's been used aggressively much, the valvesprings can get weak, which can make it go "boom" from valve-float. Replace them if you're not pretty sure they're still strong enough before riding like me. If the springs are good and the motor stock, I doubt you can really hurt it. The head and cams won't allow enough airflow to overrev the stoutly overbuilt Kawasakis. As for a rebuild? How many folks really wear-out their rings, as opposed to just glazing and sticking? Chrome rings, if not gummed-up from sitting or grandma-riding, just about don't wear. Same for the steel cylinder liners until you get into high-compression, high-heat modified engines. Every year, my (formerly my wife's) KZ650 smokes and spits oil out the breather after sitting through the cold part of winter in the garage, until it gets thrashed unmercifully for a week or two. Then it stops smoking, the blow-by goes away, and it runs smoother and stronger, until it sits another couple months. To me, that means the ring grooves have some crud in them, and if I wanted to tear it down, I could clean things up and put it together and it'd be fine. People bore these things to get displacement. I've yet to see any taper or measurable wear in any of the cylinders I've checked-out from my bikes or any of my ebay cylinder purchases (the gouge from a broken oil-ring doesn't count as wear and that was caused by sticking).

Note: I have no clue how high I actually rev the 650. The tach is a joke, but I routinely run-out of power before shifting, because a quick-revving engine with an inconsistant tach is hard to always shift at the right point when you're trying to put the maximum embarrassment on a "hot-rod" harley. Those guys hate getting smoked so bad by a 30-year-old rice-burner anyway, but when you tell them it's just a 650, not a 900 or 1000, they about blow a gasket!:laugh:

Someday I'll finish my Z1 project and start hunting real competitionB)

depends on whats been done to motor,on a basically stock motor id say no more than around 8,000 after that your not making power,youre just beating it to death;) bigger motors generally dont have to turn as many rpms to make same power thats why i like big motorsB)

Redline on my bike is 8500 RPM. I have found that I can take it to 9000 and it pulls good til then. Then I can feel it just stop pulling so I shift. Torque and HP usually occur at different RPM's though. Your manual should list what each is, so check to see. If you are racing, you want to rev it past the torque RPM so that when you shift and the RPM's drop, you will still be close to optimum torque and it will recover faster.

The Z1 / KZ900 / KZ1000 motors have caged roller bearings for the crank - this is the limiting factor. Spin the motor too fast and the rollers stop rolling and start sliding causing a premature end to the crank.

10,000 rpm is a fairly safe limit for the crank - but at 10,000 rpm you run a risk of a shim popping out or a valve floating unless you switch to under bucket shims and heavier valve springs.