how high will it spin

Hey I have a kz900 thats got an 1105kit on it and am curious how high these things will rev without coming apart.
cam specs as follows

lift .410
duration at .04 250
lobe centers 108

this is a drag race only machine and im curious what rpm to launch at and shift at

i am not sure i would think it would depend on how well the rest of the motor is built, like is the crank welded? what strength valve springs are they new or wore?

IIRC the roller main bearings are the limiting factor at about 10,000rpm.

yea and i have no idea what, if anything, has been done to the bottom end. Allegedly, the guy that built the bike launched at like 8k rpm but i am not sure. i was hoping with the cam specs some of you smart guys could maybe tell me at what rpm my power curve will decline

and i just put new valve springs in it

chancelton wrote: yea and i have no idea what, if anything, has been done to the bottom end. Allegedly, the guy that built the bike launched at like 8k rpm but i am not sure. i was hoping with the cam specs some of you smart guys could maybe tell me at what rpm my power curve will decline

Ask LarryC, but he's going to need more information that what you provided. What carbs, what size valves, any port work, compression ratio, etc?

My 1075 is for a fact "race ready" from the valve cover to the oil pan and I still won't rev it higher than 10k since its worth more than the rest of the bike.

chancelton wrote: yea and i have no idea what, if anything, has been done to the bottom end. Allegedly, the guy that built the bike launched at like 8k rpm but i am not sure. i was hoping with the cam specs some of you smart guys could maybe tell me at what rpm my power curve will decline

This really is the key because the power will normally begin to taper off before your engine over revs. Determining this can best be done on a dyno. Ed

There's no sense spinning a motor past where it makes power.

Depending on the head & carbs, it could peak anywhere from 8500 to 9500.

I watched a guy with a 1327 drag bike pound the living daylights out of the motor and it didn't go quicker. Had an 88CFM C&W KZ head with 36/31 valves, 38mm Trons and an old set of worn out 8X Andrews Cams.

He could't break a 6.0 1/8th mile with it. His buddy had an 1135 J motor bike running 6.3's with something like 14/50 gearing on it. He kept telling the KZ guy the bike needed lower gearing. KZ guy kept gearing it down and it slowed down to 6.1 - 6.3. He was launching the thing at 9500 with the limiter set at 10,000..... :whistle: I had nothing to do with that bike other than to observe and console the poor guy who was trying to get the owner to listen to him......

launching at 9500?
WHY WHY WHY
I wonder how that broke

id love to get it on a dyno but unfortunately thats not really an option for me.
the bike is actually a custom frame laydown 3 wheeler with paddle tire for sand drag racing and i dont wanna but tires just for a dyno run. the paddles will come off the tires if i get on it on anything hard packed, and at 500 each its not worth it.

i certainly appreciate all the responses guys and I think I gonna set the limiter at 10 and hope for the best. try to leave at around 8k and hope i get enough traction to actually use low gear.

I just got this thing last year and have only made 7 runs on it and it ran terribly. story behind this bike is the guy that built it made it go fast and then sold it and there has been 5 owners since then and it hasnt gone fast for any of them. I wanna be the guy that fixed it. so over the winter i checked compression and it was awfully low so i pulled the head and found that the clearances were way too tight for the valves, had 4 broken valve springs, the headgasket was obviously leaking and the cams needed to be re degreed. so i am trying to get this thing as close to perfect as i can to go shock everyone april 7th.


anyway thanks again for all the advice guys, its much appreciated.

oh, and some eye candy

You change that # and she'll run for ya.... :whistle:
I'm saying it will nose over around 9-9,500.
Flat slides would wake it up.