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Valve Tech - What's a 30 degree backcut worth?
- larrycavan
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- polkat
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- roy-b-boy-b
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1979 LTD Street Fighter.1977 KZ1000
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- timebomb33
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1973 z1 2-1974z1-a,2-1975z1-b dragbikes1015cc+1393cc, 1977kz1000,1978kz1000,1981kz1000j, 1997 zx-11, 2000 z12r,1428turbo nitrous pro-mod and a shit load of parts thats all for now leader sask.,CANADA
I THINK MY POWERBAND BROKE
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- BSKZ650
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in my mind I figured it prob helped clean up the flow around the valve also, not sure if there is any way to teast for that.
77 kz650, owned for over 25 years
77 ltd1000, current rider
76 kz900, just waiting
73 z1,, gonna restore this one
piglet, leggero harley davidson
SR, Ride captian, S.E.Texas Patriot Guard Riders.. AKA KawaBob
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- TeK9iNe
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- What did you do!?!
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Valve Angles - Make More Horsepower
They went as far as doing a double back cut, but it yielded no percievable results.
Not exactly bike tech, but still interesting :laugh:
Motorcycle Shop Owner/Operator
79 Kawie Z1000 LTD
81 Kawie Z1000 CSR
83 Honda VT750C A
85 Kawie GPZ900 A2
86 Zukie GS1150 EG
93 Yamie XV1100 E
Lucky to have rolled many old bikes through my doors
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- larrycavan
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It's one of those things where you sneak up on the amount you cut as well.
Here's some numbers for you.
Stock 1983 GPz11 with much larger than KZ port and 38mm stock valves [the're back cut from the factory]
Flowed at 10" of test pressure.
.100 - 28CFM
.200 - 58CFM
.300 - 77CFM
.400 - 82CFM
.500 - 82CFM
Here's the KZ street cut I did with J Intakes and throats at 86% of valve diameter. Bowls are only 33.5mm Runners are still smaller than a J. Flowed without a radiused intake boot that generally adds 3 - 5 CFM to the numbers.
.100 - 30.8CFM
.200 - 55.4CFM
.300 - 78.0CFM
.400 - 84.2CFM
.500 - 86.0CFM
Head will get decked tomorrow and I'll post up some pics of the completed work.
It's getting married to some Cam Motion Z1 Grind cams [.400 lift with 246@.050 dur]and topped off a rack Keihin CRS29 Smoothbores and a 1075 Piston Kit. Should make a really nice street ride...
I could take this head to an easy 90+CFM no problem with 90% throats.
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- Ktm181
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For that matter i'm even keener to get it down here to Aussie and fitted to the "old girl"!!!
Kt
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- Old Man Rock
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I'm just glad I sent Larry my head to do his magic... Give me the spaghetti electrical work any day over all this CFM spanglish... :laugh:
OMR
1976 KZ900-A4
MTC 1075cc.
Camshafts: Kawi GPZ-1100 .375 lift
Head: P&P via Larry Cavanaugh
ZX636 suspension
MIKUNI, RS-34'S...
Kerker 4-1, 1.5" comp baffle.
Dyna-S E.I.
Earls 10 row Oil Cooler
Acewell 2802 Series Speedo/Tach
Innovate LC1 Wideband 02 AFR meter
Phoenix, Az
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- BSKZ650
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Anyone here speak Japanese for I have no clue what the hell Larry just said.... :laugh: :laugh: :laugh:
I'm just glad I sent Larry my head to do his magic... Give me the spaghetti electrical work any day over all this CFM spanglish... :laugh:
OMR
Im thinkin OMR has had too many shorts in his pants:woohoo:
77 kz650, owned for over 25 years
77 ltd1000, current rider
76 kz900, just waiting
73 z1,, gonna restore this one
piglet, leggero harley davidson
SR, Ride captian, S.E.Texas Patriot Guard Riders.. AKA KawaBob
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- Patton
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Anyone here speak Japanese for I have no clue what the hell Larry just said.... :laugh: :laugh: :laugh:
I'm just glad I sent Larry my head to do his magic... Give me the spaghetti electrical work any day over all this CFM spanglish... :laugh:
OMR
1973 Z1
KZ900 LTD
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- Old Man Rock
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Anyone notice the dead guy "Patton" in the image.... :ohmy: :huh: :dry: :laugh: :laugh:
1976 KZ900-A4
MTC 1075cc.
Camshafts: Kawi GPZ-1100 .375 lift
Head: P&P via Larry Cavanaugh
ZX636 suspension
MIKUNI, RS-34'S...
Kerker 4-1, 1.5" comp baffle.
Dyna-S E.I.
Earls 10 row Oil Cooler
Acewell 2802 Series Speedo/Tach
Innovate LC1 Wideband 02 AFR meter
Phoenix, Az
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