performance cam question for a kz900

mtkawboy wrote: Just thought Id mention that if you use the GPZ cams in your 900 you lose the tach drive & need an electronic tach. I have the 260/260 395 lift cams in my 900/1105 and it is a pain in traffic or slow going. It does run strong but has the head, 10.25-1 pistons & carbs to back it up too

That's weird. My 1075 has k410's, RS34's, and CRH stage 1 port job and has perfect manners in traffic. It also pulls like a train above 4500 rpm's.

My 1197 with .415 lift 252 duration cams, 100CFM head & RS36 Mikunis carureted as smooth as a stock motor with an airbox in traffic. It also pulled in 5th fromn 2300RPM....just roll it on an go

What I've noticed is a restricted intake port with performance cams makes the engine peaky. With adequate porting, the torque spreads is much broader. It's like a dimmer switch on a light. The more you roll it on, the more it pulls.

A mean port velocity of 270 feet per second works really well on KZ motors. To get that you need area. Then you also need the correct valve size for the bore you're trying to feed.... and so one and so forth

Keep duration between about 240 to 250 degrees at .050" if you want a great street ride. If you want more power than you're going to realistically use most of the time, use 260 - 266 degrees of duration cams. But note that you need to crank up the compression to support them or you'll need to flog the shifter to get it going good under 5000 RPM.

In short, buy the parts that work well together for the bike you're going to be happy with all the time.

Pay attention grasshopper. You're getting the good stuff here.

Marked for future reference.

I wouldnt rule out the possability that you 2 are smarter then me

Larry; I really enjoyed your KZ FAQ page/write up. I've had a 76 900 "daily rider" since around 99. I stripped the bike a couple years ago to freshen it up, adding a new stator, solid state rectifier, voltage regulator, halogen headlight, etc etc, but I did not touch the motor except for rebuilding carbs. In hindsight, I wish I had "at the very least" removed the head to port it and do a valve job, but at the time my line of thinking was "it was ok before, should be ok now". This spring I did reinstall the stock air box and sync'd the carbs. Other than a Kerker, it's bone stock but it does run very well.

I'm 51, used to rebuild motors on the side (V8s), did a little drag racing on the side, and I'm doing a frame up restoration on my ole 70 Chevelle SS. I say all that just to let you know a bit of where I'm coming from, my abilities and experence. I'm good with motors, and pretty good with carbs; I just do not have the experience or knowledge with the KZ motors, or for that matter; motorcycle engines of any type. (but I have the ability to learn and understand).

Two things in my future. #1: I have a 77 KZ 1000 LTD I'd like to build for the street for me, basically the KZ that will take me to the age of no more riding. The goal on this motor would be the a good mix of output and reliability. In other words; how many pony's can I get out of it and still have decent street manners. Then; what's it take to achieve that.

#2: I have a 76 900 "parts bike" that I'm seriously thinking about modifying for the vintage motorcycle racing venue. This is a "recent" bug that has bitten me but I think it would be the most fun a person could have with their clothes on! I'm in the process of finding out what all would be required. I don't mean the rules; I have those, I mean what do I need to do to the frame, front suspension, what swing arm, what rear shocks, where do I mount rear shocks, where do I need to gusset up the frame and on and on and on.

Can you point me in the right direction? Appreciate any help you are willing and able to provide.

Chuck Marsh

RE : sprocket work
I noticed a set of J cams I have kicking around here have been ground down a bit where the sprocket bolt are. I am assuming that that is to clear the cam chain when using the earlier KZ peanut chain in a KZ motor. Is it possibel to run the J cam in a 900 ,also it is easier to run a J cam in a MKII with the larger cam sprocket? Do they sell a special conversion sprocket ? Thanks! Steve