TOPIC:

Hi everyone,

Long time reader, first time poster here. For the last year I have been building a KZ and I have this forum to thank for making it possible. You have all provided me with the wealth of information I needed to make my dream come true. My bike is now completed, and I got to take my first break-in ride last weekend. Thank you all for the knowledge you freely shared.

The Bike
1981 KZ1000 K LTD
KZ1000P 18” rear wheel
KZ1000P clutch
MTC 1135 GPZ style 10.5:1 pistons
Ported 84 bathtub style head
APE springs, studs, and head bolts
Welded 84 crank with 18mm wrist pins
Stock Cam
Mikuni RS34 carburetors
Vance and Hines 4 into 1 exhaust
Undercut transmission
530 chain with 2.66:1 final ratio

To finalize this bike, I need a cam. My question to all of you involves clearing up some confusing information I have regarding camshafts.
It seems to be common knowledge that more duration equals a higher RPM power, decrease in low RPM torque, and lower static cylinder pressure. Less duration equals better low RPM torque, decrease in high RPM performance, and higher static cylinder pressure. This has been stated time and time again on this forum but there is more I would like to know.
Specifically, how does duration, valve timing events, and lobe center angle work together to define a particular camshafts characteristic. Take for example these two camshafts,

Cam Duration@.050 Intake timing Exhaust Timing Overlap Duration Lobe Center
3X 266 (per Joe H) 37BTDC/65ABDC 65BBDC/37ATDC 74 106
Web 44 265 24BTDC/61ABDC 64BBDC/21ATDC 45 110

The Web 44 and the 3X have very similar duration specs. However, the 3X still has significantly larger valve timing events and overlap. How can two cams have nearly the same duration but such radically different overlap? Wouldn’t the lobes be of similar shape and size if the durations are the same? How would the performance of these two cams differ if put in two identical motors?
Making matters even more confusing for the consumer, the larger 3X is marketed as a street cam and the Web 44 a large displacement pro stock??

Here is another example,

Cam Duration@.050 Intake timing Exhaust Timing Overlap Duration Lobe Center
K410 252 (per Jay) 27BTDC/59ABDC 59BBDC/27ATDC 54 106
Web 110 256 22BTDC/54ABDC 56BBDC/20ATDC 42 107

These two cams are marketed similarly and their specs are very close. However, the K410 has higher overlap with less duration? Wouldn’t it be expected that the Web 110 would have higher overlap as it has slightly more duration? Is the Web 110 a lower RPM cam then the K410?

And here is yet another confusing example,
Cam Duration@.050 Intake timing Exhaust Timing Overlap Duration Lobe Center
Web 118 246 18BTDC/48ABDC 48BBDC/18ATDC 36 105
Z1 247 (per Larry C) 16BTDC/56ABDC 56BBDC/16ATDC 32 110

With the Web 118’s tighter 105 lobe center, wouldn’t it be expected to have significantly higher overlap then the Z1? But it doesn’t, there is only a 4-degree difference between the two?

I find this information confusing from a consumer standpoint. If I was trying to decide between purchasing the K410 or the Web 118, it wouldn’t appear the K410 has a radically higher power-band, but it does.
If I was deciding between the K410 and the Web 110, I would expect them to perform similarly. But it seems the K410 would still be a slightly higher RPM cam.
Can anyone shed light on how valve events, overlap, and lobe center angle define a camshaft?

Sounds like a dream bike to me, but being that I'm a little older maybe a little less so.

Please post some pics!

Does your 84 head have the valve shims on top?

My 1135 has an 84 ZN head with a set of 84 ZX cams/stock non-adjustable sprockets. It has the shims on top which makes valve-lash adjustment a breeze. Bigger cams may not work with it though.

Okay first pic, I hope this posts okay,

I only have a couple of worthy pics available at this time and the bike wasnt completly finished when I took them. I still have a lot cosmetic work to do. The PO had glued Kawasaki emblems onto the tank and they started to peel up at the ends. When I removed them it took the paint with. So now Im looking at a complete re-painting. One nice thing though, the PO had the factory swing arm chrome plated.

My bike also has an 84 ZN1100 LTD head with shim on top. I found the whole engine on Craigslst for $200. At the time, neither the seller nor myself knew it was a ZN1100. Im now using the head and crank. The block is a bored 1089 off an 82 KZ1100.

Here is another pic. This one is pre-rebuild with a vetter quicksilver fairing.

Just a reminder that aftermarket "J" engine cams are actually early KZ cams that kind of fit. The cam lobes are not centered in all buckets, the sprockets are not centered so the chain rides on an angle, and if you have a cable driven tach the drive gear on the exhaust cam does not line up with the driven gear in the head. I'm running the K410s and had the adjustable sprockets machined to center the chain.

Another choice is to pick the specs you want, have your OEM cams re-ground, and slot the OEM sprockets for timing. Web Cam who produces cams for APE can do it for you.

Thank you VTEC. I will definatly take a closer look at lobe and sprocket alighment. Guess I shouldve mentioned in the original post that I have a set of 3X's with APE sprockets. Ive never used them but I spoke with Joe at pitstop and he informed me they a powerband of about 5500--9500 RPM. I also have releived the head and valve cover to accept these cams, if I choose to run them.

How would you describe the K410's powerband?

Thought I would give an update....I found a set of used K410's for a good price so I bought them . Put them in at 105 and I'm happy with the results--bike pulls hard all the way to redline. I put on a coat of black spraypaint to get me through the season. Hopefully I'll be able to get a professional paint job done this winter. Ive attached a pic of the bike as it sits now.