Old Kaws Never Die - Big Bore Rebuild
This part of the series will describe a typical rebuild. There are many
variables that will determine how much you spend and what you end up with.
What you start with will help determine how much you spend and what you will end
with. I prefer old Kaws. The bottom ends of these machines do not wear out.
Used parts are still easy to come by and affordable. The other good base
bike is the 4 valve GS1100 Suzuki. These bikes are much harder to come by
and are more expensive to build. The top end has twice the parts of a 2-valve
motor. There are also some oil system problems. These are great project bikes
and will make more HP due to the 4-valve setup. Once you know what you are
starting with, you need to know what you want to end up with. Is it going to
be a street only machine, street and strip, or track only? Being street only
does not mean that you cannot take it to the strip. Going to the track 3 or 4
times a year or every weekend is what I am talking about. Ask yourself some
common sense questions such as; Will I ride this every day? Will I get caught
in traffic? Do I need to ride in stop and go city traffic?
The more power output you want, requires some tradeoffs in reliability,
streetability, and lifespan. The 1200cc motor that I am building is not
going to be used as a commuting machine. I have 2 other bikes that can
be used for that. These large motors will overheat in stopped traffic.
A 1075cc motor will not overheat. My 1150cc bike will start to overheat,
it has a compression of 190psig. All these motors have the same cooling
surface area. These motors came with 8.7:1 compression. By increasing the
displacement and compression ratio you increase the heat load which must be
dissipated by the same surface area. Basic heat transfer tells us that in
order to do this the motor temperature must increase higher. The cam you
plan to use may also make this effect worse. I have installed many different
cams. The hottest is the V&H modified grind also known as Web Cam grind #109.
The result was a cammy motor that really liked to run at high rpm. I have never
seen a power curve of this cam, but it is a top end grind. (0.425 lift and
260-degree duration @0.050 lift) It likes to be revving high, and it will rev
higher and easier than the other cams I have mentioned. For those of you who
are not familiar with the term cammy, it idles funny and can surge. This will
vary with other aspects of the motor. I have installed and degreed a 0.395 lift
with 256 degree duration @0.050 lift. Web cam grind #110. That is a decent cam
and has excellent street characteristics. Not as cammy as the other grind. I am
using the Web Cam grind #119 for this 1200cc motor and grind #110 for another,
both will have a very good idle. All cams should be setup with a 106-110 degree
lobe on the intake cam and 108-111 degree lobe center on the exhaust cam.
The Yosh stage 2 cam and the Web cam grind #119 or #110 are my idea of daily
rider street grinds. These are streetable but still permit you to rev to 10,000 rpm
depending on the timing you use. That isn't bad for a 2-valve antique. But if you
want more top end you need a hotter cam. There are some carb accelerator pump
adjustments that need to be made in order to minimize surging. A clue here is that
a smoother idle will produce less heat at idle. Revving and a higher idle will
produce more heat. Play around and find the adjustment you like.
Now that you know what you want, it's time to get dirty. The 1200 motor needs
new sleeves. The upper half of the case needs bored to accept these bigger units.
I send everything out by UPS to APE. It takes 3 boxes. I send the upper case,
cylinder jugs, and crank out. The crank gets welded. The upper case gets bored.
The old sleeves are removed, the block is bored, and new sleeves get installed,
bored, and honed. Everything comes back along with the piston kit. For a 1075cc
motor you only need to bore a 1000cc motor, but a 900cc motor requires new sleeves.
If you will need sleeves, you might as well go with a 1200cc motor. It costs
the same. If money is tight, get a used cylinder block from a boneyard. I got
one for $75 in Oct '97. That is cheaper than sleeving. An 1135 motor is the
actual size of the 1150cc Suzuki motor in the GS1150. I always refer to my
1150cc Kaw. It's actually an 1135cc motor. Building a 1075cc motor will run ~$500.
While any kit that requires new sleeves will run ~$900 and up. All this is just
parts and machine cost. You must do everything else yourself. If you are going to
pay someone to perform the work for you be prepared to spend much more. Beware of
who you pay to do your motor. Many places will learn how to do it at your expense.
Only use experienced persons. Many racers have shops, use them, not dealers or
automotive types.
The transmission is another place you can spend money on a high
performance engine. There are special gears and machine work that
can be done to beef up your tranny, 2nd gear specifically. I had to
replace the 2nd gear output and high gear output, which is the 2nd gear
input. These are the 2 parts that make up your 2nd gear on an old Kaw.
One has the 2nd gear engagement recesses and the other the engaging dogs.
The dogs wear and round off and so do the recesses. You better make sure
you at least have good parts before you reassemble. If you are willing to
spend the money undercutting the dogs and recesses it's worth it. This years
project is getting a MRE race cut tranny.
Install a new cam chain even if you have a low mile motor. The OEM chains
are a weak link. You are increasing stress on the chain due to valve train
mods such as heavy springs, higher lifts, and more rapid accelerations. A $35
cam chain now may prevent a case split later on. Do not use automatic tensioners,
they are a failure waiting to happen. Use a manual unit and take great care to
adjust it properly. Take care to inspect all cam chain gears, idlers and guides
and replace any worn or damaged parts. The compression ratio is determined by
the ratio of swept volume with unswept volume. I have decided to use a J model
head on this motor. That changes that ratio. The J-head has a larger combustion
chamber volume than the older heads. A 2-point drop is the result. I am going
with 13.5:1 pistons, which should give an 11:1 result. The actual result is 215psig
when I did a compression test. Do not pay much attention to compression ratio numbers,
the real compression is the pressure you measure on the gage, those are the numbers
that matter.
Take care in slipping the jugs down and over the pistons. I use my fingers
to compress the rings one at a time. This is no big deal; it takes about 10
minutes. The trick is to stager the top ring front and 2nd ring back. Insert
and tip the pistons slightly in the bore. Use you fingers or Popsicle sticks
compress the rings. Once all the top rings are in tip the pistons the other
way and repeat for the 2nd ring. Make sure the rings are arraigned properly
and that they are installed correctly. Do not continue assembly if you are
not sure. Just double-check everything as you go. Take care that the oil ring
expander is correctly installed and not damaged.
You need to attach a degree wheel on the alternator side of the motor
to degree in the cams. Install everything IAW your shop manual. If you
are using slotted cam sprockets, make sure you know what you are doing
so you don't put the intake cam in wrong. The timing marks are different
than the stock units. Use a 40 or 42 mill thick piece of solder to check
for proper valve clearance. The solder will squish and you know you're too close.
Use a positive stop to find TDC. Rotate slowly until the piston
touches the stop. Note the degree wheel reading. Rotate in the
opposite direction until it touches again. Note the reading.
Exactly œ way between the 2 readings is TDC adjust the wheel.
Repeat until the degree wheel reads the same BTDC and ATDC on the wheel.
There is only one place you can put your dial indicator on a KAW for WEB cams.
The first time I did this, I used a V&H video to do it. This is not easy like
everything else. Get one of those videos and watch it over and over and refer
to it. Do it exactly as they tell you. I only do this twice or thrice a year.
I still refer to that video before I start to remind myself how to do it. This
is the lobe center method. You are positioning the cam such that the center of
the lobe, highest point, has the exact timing you want. The cam I am using has a
recommended 108-degree lobe center for both intake and exhaust. These numbers can
be considered VooDoo majic. Top end power increases with a 110 degree lobe center.
Many cams come with recomended lobe centers of 106I and 109E. Many racers swear by
109I and 111E. Whatever you choose stay in the range of 106-110I and 109-111E.
Make sure you use proper torque and lock-tight the cam sprocket bolts. If they
slip during use your valve timing is gone and your motor will run like crap or
worse. All the major vendors have a video for $30. Well worth it. As for the mag
base and dial indicator, you can pay a lot depending on what you buy. Find a Starret
dealer, industrial supply house, get a basic mag base, a 2 or 3 inch dial indicator
with a 1" travel. You will need an extension tube for the shaft to clear the cam lobe.
Figure on spending $75-$100 on it. They tell you that you will get 5HP from this on
the mild cams. Most RAD cams won't work without it.
Very few people really understand cams. You hear them described in a
mishmash of terms, usually all wrong. Here are some terms and definitions.
INCHES OF LIFT- the distance the cam opens the valve.
DEGREES OF DURATION- the duration in which the valve is open during a
360 degree rotation of the engine.
LOBE CENTER- the timing in which the highest point of the cam lobe is in
relation to crank timing.
More confusion ensues when the duration is defined according to lift.
Manufactures such as Kawasaki say that they have 280 degrees of duration OEM.
They give no reference. That means @0.001 inch lift. Aftermarket usually give
@0.050 lift as the reference. Some now give @0.030 inch lift. The OEM cams
could be described as having 220 degrees duration @0.050 lift. You simply ignore
the time the valve is open until it is open a distance of 0.050 inches. Then
measure duration until the valve is 0.050 inches from closed. According to the
OEM method these cams would then have duration of 300+ degrees. The makers using
0.030 lift as the reference are tricking people to buy the right cams. Everyone
wants to buy more cam than they need or want. By advertising 256 degrees of
duration @0.030 lift you may think that is close to 260 @0.050 lift. It is not.
256 @0.030 is closer to 250 @0.050. You can measure this using a degree wheel.
My Old Kaws Newer Die Series
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