83-84 GPZ 1100 cams

otakar wrote:

DFIGPZ wrote:

FYI 1983 / 1984 GPZ 1100 cam specs:

INTAKE CAM .354 lift 238 deg

EXHAUST CAM .338 lift 239 deg

hope this helps.
Barry

The Megacycle diagrams tend to agree with you. I know that the standard "J" series intake cams are about .330 because I just measured them. These came from an CSR, that I just measured. Boy that makes me feel really radical, running .420 intakes and .410 exhausts. with 38.5mm intake valves, on my every day rider.

Nothing wrong with that i have 420 lift cams i have done for 900s with 1075 kit ported heads still running SOT retainers W/O issues.

DFIGPZ wrote:

It is a good drop in cam for Z1 900 or KZ1000 stock Z1 900 cam specs :

INTAKE 327 lift ? 237 dur
EXHAUST 296 lift / 229 dur

also you have to remember 83/84 GPZ 1100 had the highest flowing stock cyl head available, also had to run within the constaints of the DFI system and the factory redline was 9,500 rpm. so in other words it DID NOT need extreme cam size on account of head flow. This made for a wide broad power curve. hope this makes it understandable .
Barry

That is the same head I am running on my bike with the .420/.410 cams and oversize valves. Plus my head was also ported quite a bit. Plus it is an 1150 with 11:1s

There is so much confusion regarding the lift on these cams, I was planning on putting them into my bike next month to replace the J cams (just what buda did) but I thought they were .375 lift. In a thread several months ago people measured them at .375, whats the deal?

9am53 wrote:

There is so much confusion regarding the lift on these cams, I was planning on putting them into my bike next month to replace the J cams (just what buda did) but I thought they were .375 lift. In a thread several months ago people measured them at .375, whats the deal?

Install them they are an upgrade from the "J" cams.

According to my research, the "big deal" was an increase of .8mm (.0315")over the standard cam. So at the +/- .328" lift on the stock bikes that would make sense at about .360"+/-. So they definitely would be an upgrade, but just not as much as people thought.

Here is a section of an article from a 1983 review of the engine/bike, where the cams are concerned.

"To go with these changes the camshafts have been reprofiled to give more lift and duration. Both valves now have 0.8mm more lift, and they open six degrees earlier and close six degrees later than before. The valves are also bigger: inlet diameter goes up 1mm to 38mm and exhaust up 0.5mm to 32.5mm, with its angle steepened by one degree to allow this. Uprated springs keep the valves under control; setting clearances is more difficult than before because, with shims now beneath the buckets in the style of the old Z650, the cams must be removed to change them. Other mods of note are hand porting of the inlet tract to smooth out the flow, beefier conrods and an ignition which is now advanced electronically instead of mechanically.

What all this adds up to is a motor in a pretty high state of tune for a big road bike — a motor producing phenomenal peak horsepower at the expense, it must be said, of some low and mid-range grunt. There's precious little doing below six grand, so it's no use pootling along behind a line of cars at about 60mph in top and expecting them to open the throttle and scream past them. Trying just that results in a bronchial slow-progress situation and, if you were expecting instant full-bore acceleration, a terminal head-to-head confrontation with any traffic that might be approaching from the opposite direction.

In other words of one syllable, it don't want to know, John. The revs rise pretty slowly to the magic 6000rpm figure, at which point the various gasses start going where they're supposed to and the GPz shoots forward (you're already doing about a ton at this point, of course) like the street racer it is. And no sooner are you starting to enjoy this sensation than the tacho hits eight grand, the motor breathes even deeper and the speedo rockets on from 120mph to 130, 135 ... and more if you've got the road and the balls to spare."

The last paragraph in that section of article I have experienced every time I punch my bike. My magic # on the streets seams to me about 3000 and on the highway also the 6000. But with my .420 lift cams the bike is brutal. Even with the 2.22:1 gearing I am running when stock used to be 2.73:1 For the short time I ran the stock gearing, I had a hard time keeping the front wheel down on the ground while hard shifting from first to second and second tho third. Even with my gearing the front end pops up while shifting from first to second, if I'm really standing on it.

Look at the bottom of this thread where Tim measured the GPz cams and says .375-.380. The .328 lift may have been the CSR or LTD cams, but I presume the .8mm increase your article states refers to a set of 81-82 GPz cams, or maybe a standard J cam

kzrider.com/index.php?option=com_kunena&...ew&catid=2&id=321585

9am: Havent you just gone from the K-M "cruiser" cams to the J spec cam? I did the same thing.I think what u r going to find if u go to the Geep cams is an increse in top end offset by a loss in low to mid range torque.If ur bike is anything like mine (and I believe they r clones) mine dynos at a little over 80 rwhp with the same set-up u have.Larry C says he can get 10 more rwhp by a fairly straightforward head port.I think I am going in that direction-just to give u another option.Will keep u posted.Please let me know how ur cam swap works if u go that way as well.with a 125 -130 mph bike (by dyno) already,I dont need any more top end.Lol.bj

9am53 wrote:

Look at the bottom of this thread where Tim measured the GPz cams and says .375-.380. The .328 lift may have been the CSR or LTD cams, but I presume the .8mm increase your article states refers to a set of 81-82 GPz cams, or maybe a standard J cam

kzrider.com/index.php?option=com_kunena&...ew&catid=2&id=321585

i would say look at larrycavan post in the thread you posted #321743 he states GPZ approx 360 lift. buy them measure for yourself my 84 cams DO NOT measure 375 or 380 for whats its worth. in the end its all in what you want.

I have a set already, I guess I could measure them and find out for myself, just not sure exactly how to measure...it is the total height of the lobe minus the base circle diameter?

The one you are interested in is the intake cam to measure. Take the cam and measure the base circle of the cam lobe. This means from side to side the round part. NOT from base of lobe to tip of lobe! While you are measuring it, zero out the calipers. Now with the calipers being zeroed out on the base circle, measure the lobe from tip to base, than subtract .005" to accommodate the shim gap. That is the lift of the cam.