stock cam lift

does anyone know the stock cam lift of a kz650 or kz50 4?
i'm looking at cams and would like to know what stock is..

Stock lift for a KZ650 is 8 mm/0.314 inch.

Just measured my stock Kz650 cams and they had .304" of lift and 220 degrees of duration. And my kz750 cams measured out to .320". The 750 cams also have more duration. GPZ750 cams have .354" lift and 250 duration.

wow! alright.. thanks for taking the time to measure that out. I was thinking the .395 lift and 284° duration. is the .400 290° , says it's for road racing, but not much of an increase from the hot street cam. Or is that just a bit too much? How do you think the idle will be with either of these cams? what's considered mid range and top end? 3000 rpm and up? I'm never really under 4000rpm anyway.

Those cams would prob be a bit big and "peeky" with a 650 and stock compression. Might wanna check out MegaCycle . They have one that is in between Web's and they are a fuzz cheaper.

no, i have a 77 650 motor and i just bought an 81 750 jugs. going for the 810cc wiseco. i'm looking to see what i should put in that. sorry, i should have specified. i did want the stock lift to compare to though. do you think those cams i mentioned are too beefy for the 810cc?

Oh, ok. I am doing the same thing, jugs are at the machine right now. I think it work out better then. But honestly the last think you wanna do is go too big on the cam cause it wont be nearly as fun on the street. I prob gonna go with the Web cams that are just bigger than the gpz750 cams. I'm doing this cause I want to keep my tach drive.

ok, I was just talking to this guy who has the 810cc set up on his 650.. He said he has 80 RWHP with stock kz750 cams. What kind of HP increase would there be with the .385 or .395 lift.. Will the bike idle ok?

I'm in the same boat myself

The big question is the heads, as in what is the stock flow at different valve openings for the KZ750 head vs the GPz750 head. If the flow stops at .360" lift, then a .395" lift wouldn't do any good.
Since the stock 83-85 GPz750 head is supposed to be the best flowing one, maybe those of us planning on using one should talk to Larry Cavanaugh about checking the flow for us.

I have seen absolutely no info on flow or porting the 750 heads, it all about the 1000's


How about it Larry, can you cut us a deal?

steell wrote:

I'm in the same boat myself

The big question is the heads, as in what is the stock flow at different valve openings for the KZ750 head vs the GPz750 head. If the flow stops at .360" lift, then a .395" lift wouldn't do any good.
Since the stock 83-85 GPz750 head is supposed to be the best flowing one, maybe those of us planning on using one should talk to Larry Cavanaugh about checking the flow for us.

I have seen absolutely no info on flow or porting the 750 heads, it all about the 1000's


How about it Larry, can you cut us a deal?

Ship one and I'll flow it for you. You pay shipping both ways...no charge to flow test it....

Regarding the flow sign off lift. It's ok to lift the valve past the sign off point. When picking a cam for your bike, one way to decide on minimum lift is to multiply the valve diameter by .25 [convergence lift]

Example: [As I recall the 85 GPz 750 had a 35mm intake] Can't remember what the 650 had. Probably a 34...anyone?

35mm Intake Valve = 35 * .03937 = 1.377"

1.377 * .25 = .344"

You'll find most cam manufacturers offer a cam that lifts the valve to very near the convergence lift of the valve.

The convergence lift is where the curtain area equals the valve area [within reason]

In other words, without porting the head, you'll at least take full advantage of the area offered by the valve size.

Often that will be the next cam beyond the drop in cam offered by the manufacturer. Here's a couple of the old Andrews cams offerd for the 650 back in the day...

#10 Grind - .330" lift 236* Duration - Drop in
#20 Grind - .340" lift 244* Duration - For 750 engine
#30 Grind - .350" lift 260* Duration - Modified engines through 1982

Obviously lift alone is not the final say but if you're going to go beyond the drop in but wanting to stay away from anything that needs further mods to make it come alive....the grind that's closest to the covergence lift is generally a very good choice for the street with moderate compression motors.

When calculating the required lift for a motor to achieve a specifice design goal, the valve size and the cam lift are used in conjunction to obtain the required curtain area. That can be used in conjunction with the minimum required flow the engine needs to achieve 100% & greater efficiency. It all adds up to the flow you need at a specific lift to obtain a peak horsepower RPM you're after. Get it right.....twist grip heaven...

So for example it's possible to yield a required curtain area from either larger valve or more lift...just depends on the situation. As in all things related to the internal combustion engine...there's more than one way to achive an area requirement.



Larry C

From the GPz FAQ (no idea if it's accurate)
gpzrider.lagemann.org/technical/FAQ2000.htm

Although the valve angle is the same, the 750 has larger valves (33mm intake 29mm exhaust)

Guess I could get off my lazy butt and go find a caliper and measure the valves

Edit:

That statement above is comparing GPz/KZ750 valves to KZ650 valves. AFAIK, the GPz750 and KZ750 valves are the same size.

so, if i use GPZ750 valves on a KZ750 head or a GPZ750 head, the max lift on a cam shouldn't exceed .350 lift? If I used a bigger cam say .385 or .395 what else would have to be modified w/ an 810 kit? What happens if you mill the head?