DO NOT use lead free solder. The stuff you get at the local home center
is 95% lead free and solid (no core). This type of solder will not smash properly and not give a
proper smash and will not give me the correct information needed to machine your
Use at least a lead / tin cored solder. A cored
solder like "acid core" or "rosin core" will give you the most accurate
You can find .093" (3/32") Rosin cored solder at your
local NAPA auto parts store Part Number: 31406 Suggested use on most YZ, RM, KX,
You can find .125" (1/8") Rosin cored solder at your local
NAPA auto parts store Part Number: 32406 Suggested for gasgas and some KTM and
Husky 250 and 300's
For smaller bore Japanese engines you can find .062" cored
solder from RadioShack Part Number 64-007
and understand the following before measuring squish
Keep in mind that your head will be machined using your supplied test solders
These test solders are my
only look into your engine so that I know what needs to be done without actually
having the engine in front of me. So, it is very important that you pay close
attention to the process and do the solder tests with great care. Your head will
be modified using these solders that you have provided me.
As you can see in the
example pic's below, (these pic's are examples only and
may not show your particular engine, but the idea and process is the same)
the solder is to lay flat across the top of the piston, over the center line of
the piston pin with a small "camel hump" that also lays flat on top of the
The pic's below are examples only, your engine may
a little different, but the idea is the same for most all two stroke engines.
last note before you go on to the actual Measuring
Squish, make sure that the ends of the solder touch the cylinder
wall on both sides and that both ends are cut blunt and clean
(blunt and clean on the ends is very important).
These are examples of how your
test solders should look.
reason for the small hump is to allow you to either pull the ends farther apart
or push the ends closer together. This will allow you to get both ends of the
solder to touch and rub on the cylinder wall.
hump shape of the solder is to lay flat on top of the piston, also this will
keep the solder from moving around and help keep it in place.
It is also very
important that the hump shape of the solder does not come in contact with the
squish band area.
last note before you go on to the actual Measuring Squish,
make sure that the ends of the solder touch the cylinder wall on both sides and
that both ends are cut blunt and clean
(blunt and clean on the ends is very important).
Again I can not stress
enough the importance of the solder tests. Send at least 3 tests solders with
the head to be modified, they are easy to do.
The test solder below were done
These are some examples of poorly done solder tests. You must
keep the hump shape of the solder small enough, so it will not come in contact
with the squish band. If this hump shape comes in contact with the the squish
band, it will deflect the piston and may give an incorrect reading on the ends
of the solder.
Picture to the left was done
incorrectly as the hump was smashed
It is very important that the ends of the test solder are cut
clean and blunt. This is a very critical area to be measured, it is this
measurement that will be used to do your head modification.
Picture left was done
incorrectly as the end is rounded, not blunt
Now it's time to Measure Squish Band Clearance
The best and easiest way to
do this is by using a piece of rosin-core or acid core-solder
(Do not use a solid, core-less type of solder). You
can buy the rosin or acid core solder from your local hardware store, auto parts
stores or places like radio shack. The solder needs to be thick enough to smash
slightly but not so thick as to bind the engine (after you
do it a few times you will get the hang of it).
The first thing you need to do is remove the
flywheel cover, this will allow you to turn the engine by hand. Next
will need to remove the head and save the old head gasket if it uses one and
re-use it when you do your solder test. Some engines do not use a head gasket, they use o-rings
and the o-rings are not necessary for this test.
Next you will need
to bend your test solder into a hump shape shown in the pic’s above, then fit
them into the bore making sur the ends of the solder touch/rub the cylinder
walls on both sides.
Now turn the flywheel by
hand or use a wrench on the flywheel nut and lower the piston about 3/8" to 1/2"
below TDC. Note, you do not want to move the piston down any lower than this
during the testing procedure.
The test solder needs to lay
right across the center line of the piston pin (3 o'clock 9 o'clock) . Make sure the ends of the solder
touch the bore of the cylinder on both sides. You can use a small dab of grease
on the hump shape that should be laying flat on the top of the piston also, this
helps hold it into place.
Next install the head and use
your old head gasket if it used one (o-ring seal type
of heads do not use a head gasket and the o-rings are not necessary for this
test) and snug it down with the head bolts/nuts. Now carefully turn the
crank shaft rotating the piston over TDC by hand with a wrench on the flywheel nut.
You will feel a slight bind and this is normal. Rock it back and forth a couple
of times over TDC and then remove the head. It is not
necessary to move the piston any more than about 3/8” to 1/2” below TDC.
DO NOT USE THE
KICK STARTER TO ROTATE THE ENGINE, TURN THE FLYWHEEL BY HAND ONLY.
You will see where the solder
was smashed and this is your current squish band clearance. You will need to
send at least 3 of these test solders to me with the head to be modified so I
can re-cut your head for an optimum squish band clearance and volume.
Thank you, Ron