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stock cam lift
- vach
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i'm looking at cams and would like to know what stock is..
1979 kz650 B. Chicago, Illinois
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- OnkelB
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77 KZ 650 B1, 82 GPz 1100 B2.
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- kxhonda
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1977 Kz650B1 #576th made.
Warsaw, In
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- vach
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1979 kz650 B. Chicago, Illinois
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- kxhonda
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1977 Kz650B1 #576th made.
Warsaw, In
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- vach
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1979 kz650 B. Chicago, Illinois
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- kxhonda
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1977 Kz650B1 #576th made.
Warsaw, In
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- vach
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1979 kz650 B. Chicago, Illinois
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- steell
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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?
KD9JUR
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- larrycavan
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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
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- steell
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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.
KD9JUR
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- vach
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1979 kz650 B. Chicago, Illinois
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