Perhaps the most important modification that you should make before any other,
on all air cooled bikes, is to install an oil cooler. Why? Everything you do
which increases the power output of an engine also increases the heat output.
This is no mystery. The byproduct of the internal combustion engine is heat.
The more power output, the more fuel you burn per minute the more heat you
produce per minute, the more heat output. Adding an oil cooler increases the
heat removal capacity of your motor and prevents oil temperatures from exceeding
the breakdown point.
Anyone, who has increased the compression ratio of their motor, either by using
popup pistons or by milling the head, can verify the huge change in engine operating
temperature that resulted. For example the OEM compression of 900 and 1000cc Kaws
is 8.7:1, 130-160 psig range, while a 1075 or 1260 motor with 10.25:1, 190-220 psig
compression range, a combustion temperature difference of over one hundred degrees
results. What does this mean? The engine combustion occurs at much higher temperatures
and produces more heat per stroke in order to produce more power. If you have ever
been around bikes that have these motors you can feel the heat just standing next to
them. I will leave this explanation at this level; you can get more specific if you
use some heat transfer and thermodynamics engineering references.
There are a lot of options here, but I will tell you my way. I do not use any kit
or factory parts. I modify the oil block on 73-80 Kaws, this also works on most bikes.
You can also replace the oil blocks with small rectangular aluminum blocks with
mounting holes drilled in them along with the oil port which should be tapped for Œ NPT
fittings. In some applications you must block the regular supply port to the main oil
gallery and use a secondary supply port. You must almost always do this in order to
use a big block on a Kaw. The fitting at the side of the block by #4 cyl. is an obvious
example. That is the factory test connection described in the factory manual. Most
aftermarket kits use this connection. I only use this connection on J model Kaws and
when I use big blocks.
The pictured example here works for 73-80 Kaws specifically, but most 2 valve motors
are very similar. Most 4 valve Suzuki motors come with oil coolers, there are some
exceptions, and mounting is obvious on these models.
There are 5 basic components in an oil cooling system.
1) Heat exchanger - require that this be in the wind, but clear of forks in full left,
right, and compressed positions. It should not block airflow to the engine or come in
contact with the engine or exhaust header.
2) Oil pump outlet fitting - this should be a Œ"NPT on the end that fits into the oil
supply block and a 3/8" or œ" hose barb to connect lines.
3) Main oil gallery supply fitting - this fitting has a hose barb and the correct fitting
on the other end. Many types of fittings are available from industrial supply companies.
The metric threads on the test connections on many bikes are standard. With a little
imagination you can adapt any fitting to the needed hose barb connection.
4) Oil pressure gauge - this is optional if you are able to keep your oil pressure
idiot light. If you loose the light, this is absolutely mandatory.
The heat exchanger I use is an advance design unit I found in a JC Whitney catalog.
The dimensions are 1.5"x3"x11" and has 24 horizontal plates. This unit has about
10-20 times the heat removal capacity of the old Lockhart units. This is the smallest
unit available, and meets all criteria for these old kaws and costs $41. This unit is
easily fitted onto 73-84 Kaws with some standard hose nipples and fittings.
The hose I use is a premium product, Goodyear ACALA. Why? This will be obvious if
you cut corners and have a hose pinched or blow off a hose barb. This is a push lock
type hose. It only goes one way on a hose barb. It will not pull off even without a
hose clamp. You still use hose clamps to prevent leaking and for extra security. This
is a tough hose it will not pinch closed and the heat will not effect it. You will have
to get this from an Industrial supplier.
The fitting you will need will vary depending on your specific application. For the
cooler I use a 1/4" MPT to 1/2" MPT, a 90 degree 1/4" FPT elbow, and a 1/4" MPT to hose barb
connection. Everything else should be fairly obvious from the photos.
On applications were you must use the test connection on a motor you will have to
look around to find a 90 degree rotating fitting with the right threads to screw into
the case. I do not have a source for you on this; I rummaged around a couple boneyards
and found several aluminum ones. Take a good look at the photos as for how it should
look in the end. Hose routing is key to keep them out of the way of the carbs. The
routing should follow the inside of the frame. Cut the hoses long when you start and
start them from the cooler. Keep several extra inches of hose that you can tuck out of
the way. This will give you slack to move the hoses out of the way to do maintenance
and in case you need to remove a hose you will have enough extra to re-use it. Remember
the hose must be cut from the nipples, it will not pull off. There is plenty of room to
tuck hose to the side of the battery box of behind a side cover.
I use inexpensive general-purpose gauges, $6, and about 10 ft of hose, $20, for each bike.
The brass fittings are not the cheap. They run a few dollars each, $30-40 total. If you
take into account hose clamps and teflon tape you are still under $120 for this vital
high performance system.
Make absolutely certain that there is a flow path from the oil pump outlet to the main
oil gallery. All you have done is diverted the normal oil flow through the cooler prior
to entering the main oil gallery. Some motors have 2 main oil galleries and require the
oil lines to split into 2 lines coming out of the cooler. Be care full to understand what
you are doing. You must understand that if you screw this up, the motor will be ruined.
Most service manuals have an oil gallery map that shows the flow path of the galleries.
It is well worth your time to plan this well ahead and do your homework. The reason I am
going through this is for the enthusiasts who would like to do their own work. Some riders
are better off having someone else do this work for them. Most places will install oil
cooler kits if they sell you one. The problem is that those kits are not designed for
modified bikes. They have very small coolers with small heat transfer capacities.
This is an example of how it should look when it's done. The oil gauge needs to remain
clear of the oil filler plug, the kick-starter, the carbs, your leg, and anything else.
Keep the oil lines clear of all throttle cables, fuel lines, crankcase breather line,
idle adjustment screw, etc. This addition is not difficult, but it does require
patience, imagination, planning, and some technical expertise.
The oil cooler will keep your oil cooler by removing heat from it prior to engine
lubrication. The added oil capacity of ~1 quart if you go with the œ" lines or about
œ quart for the 3/8" lines will extend oil life in the sump. You now have more oil
doing the same work as before and at lower temperatures. If you are careful and use
the same parts as I have described, you will have a heavy duty, high capacity, and
zero maintenance system that will equal or exceed any in use on any racetrack.
For those of you who have different bikes and want to use this setup I have a few
1) Match the oil pressure gauge range with your oil system. Some bikes will need to
use a 0-60 or 0-80 psig gauges. Motors with journal bearings, plane bearings, need a
higher oil pressure.
2) You may want to find some parts at a boneyard for modification. Oil blocks and
fittings do not always work or hold up if modified improperly. You may want a spare
around in case the first try doesn't work.
3) You will probably want to move the horn to a hidden location. The horn location on
many standard bikes is where the oil cooler should go. In many cases go with a single
horn instead of dual and move it inside the frame and high behind the neck.
4) Always make your lines extra long. You can always shorten up, but it's hard to make
I mentioned that it was easy to mount this thing. I will get more specific. There
are 2 ways to do it. On 73-80 frames there is a 1/4 inch ID tube that runs horizontal
just below the neck and between the down tubes. Using 1/4 -20 all thread rod and
2 small L brackets the cooler is mounted. You will have to adjust height so left/right
movement of the fork stops before hitting the cooler. You may have to bend the L into
an S sort of thing.
For most other applications there are holes present already in the area. You need to
make a small rectangular plate with 4 holes, 2 holes for the cooler and 2 for the area
between the down tubes. The horn mounting holes or studs can be used on many bikes.
That's all I can think of. Use cable ties to hold and position the lines. You can get
fancy and paint the brass fittings and put stainless steel braid over the lines of course.
Just make sure the oil path is proper and unrestricted. Planning and care will save time,
money, and brain cells.
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