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Kz 1000 Head porting
- gearhead119
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2000 Zrx1100 Turbo-220bhp/145lbs torque
1978 KZ 1000 project-in progress
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- PLUMMEN
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- larrycavan
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How big you you make the port is relative to how big the motor is and how fast you're going to spin it.
Here's an online calculator to help you out.
www.rbracing-rsr.com/calculations.htm
In the attached picture, I put a yellow line at the throat of the port. If this is a small bore street motor, measure that diameter and make it 90% of the size of the valve.
36 * .90 = 32.5mm
The runners are looking pretty good. Keep them nice and level. Avoid getting low spots in them.
Stock flow on those heads is generally 68CFM@10"water @.500" lift.
How big is the motor?
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- larrycavan
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When you do the valve job, push the seat all the way out to the edge of the valve and then use the outside cutter one more time to narrow the 45 up so there's a thin, shiny line just outside the 45.
If you're cutting the seats by hand with Neway cutters, watch you don't get going crooked with the cutter. The T handle will quickly rock and the cutter will follow a crooked seat in a heart beat.
Best to just go in there first with a 60 and put a light cut in there to see how crooked things are.
Then, take the 30, go easy, keep the cutter straight and wipe the 45 right out. Go back with the 60, set your inside angle to the width you want, then cut the 45 lightly.
Put magic marker on the seat and set the valve in there. DO NOT SPIN IT. Pull it out and see where the seat locates and more importantly, how evenly the marker is dispersed onto the valve. It's a quick/easy way to check your concentricity.
Then adjust the location with the 45 and set outside location with the 30 and width with the 60.
If the head has never been touched, you're going to find the exhaust valves are seated way low on the face. They can be sunk a bunch to push the seat further out on the valve face.
The handiest thing you'll want is a 37.5mm round block to drop down in the bucket bore to check your stem height. You can make one or APE has them for an inexpensive price. I use mine all the time.
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- Motor Head
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- FIX UP YOUR BIKE RIGHT AND CHEAP
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I love the work, done a lot of heads and 2 stroke cylinders. One place I worked in the 80's had a head flow bench. Some very wise people have been doing a rougher port contour on the inside closest angle of flow. And mirror polishing the outside angle of flow. Fuel droplets follow the inside track, and the lighter air flows around the outside of the curve, some roughness helps keep the fuel atomized. Also you may consider either narrowing the outside diameter or the valve guides or shortening them. Some of the KZ head guru's would know about longevity issues with shorting them. Also I didn't see if you retained the stock valves or were going stainless. Stainless will out flow the stock valves, you can also relieve around the valves in the head in the chamber, with a CC equalization, and polish. Then if you have the tools some more gain can be had from doing a 5 angle seat cut, but its really most noticeable when flow benching, once you do the port work and reassemble it will pull like crazy, so all little details will be in or out of the finished head.
Camshaft grind and carb work with a raise in compression, 4 into 1, ignition curve, etc will make it all work. Just hold on tight!
1982 KZ1000LTD K2 Vance & Hines 4-1 ACCEL COILS Added Vetter fairing & Bags. FOX Racing rear Shocks, Braced Swing-arm, Fork Brace, Progressive Fork Springs RT Gold Emulators, APE Valve Springs, 1166 Big Bore kit, RS34's, GPZ cams.
1980 KZ550LTD C1 Stock SOLD Miss it
1979 MAZDA RX7 in the works, 13B...
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- gearhead119
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As far as port texture... it will probably stay roughed up a little... on the intake anyway... exhaust may be smoother.
2000 Zrx1100 Turbo-220bhp/145lbs torque
1978 KZ 1000 project-in progress
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- kzz1p
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- One Test Is Worth A Thousand Expert Opinions!
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What carbs are you suggesting?
What is the motor to be used for?
In performance, you must give up something, to get something. What are willing to give up?
What is your intake port volume? What is the combustion chamber volume?
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- larrycavan
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The flow is in the bowl on those heads
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- PLUMMEN
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absolutely! easiest way i know to illustrate this is with plumbing fittings this first picture is a vent fitting,2nd is called a long sweep.same size pipe/port feeding each.which one do you thing drains/flows better?Street Applications - Taper but don't shorten the guide. It has an important job to do.
The flow is in the bowl on those heads
Still recovering,some days are better than others.
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Still recovering,some days are better than others.
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- irishwill
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a bulb just went off
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- TexasKZ
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1. If I understand Plummen's pvc example, then one of the goals is to remove some material at each end of the long radius (top of the port) and to remove some material from the center of the short radius (bottom of the port). Is this correct?
2. If I assume a set of 29s are going on and I use the 90% formula larrycavan posted above, then is it correct to assume that another goal is to have a gradual taper from 29mm to 32.5mm?
1982 KZ1000 LTD parts donor
1981 KZ1000 LTD awaiting resurrection
2000 ZRX1100 not ridden enough
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