How to Rebuild The
Cushman Cast Iron Engine Manual
The Step by Step Overhaul Guide
Supplemental
Information Center
Click
here for more information on the Engine Manual
Click
here for CAD drawings of Engine Tools
Last update
06/13/08
6/15/00 New Information on removal of
side plate races: I have made tools that will press the races out
of the block and out of the felt seal type side plate very easily.
Removal of the races with the tool distorts the oil retainer
slightly but
it is easily flattened back out and can be reused. I also made a tool that makes
installing the races very easy. CAD drawings of the tools
will be posted soon. The cone in the newer side plate using a
neoprene seal must still be removed with a punch. 6/18/00
Reference to the manual page 15 paragraph 3. The manual says to
install the side plate (with the seal already installed in it) and
verify the end play, then remove the side plate and apply sealant and reinstall. Due
to the difficulty in pressing the seal over the crankshaft you might
want to wait to install the seal in the
side plate until this step has been accomplished. (or see the tip about
this problem below) 6/18/00 Tommy
Goode3 in Texas makes a dandy engine stand that is really helpful when
working on a Cushman engine. A flange on the engine stand bolts to the
two holes on the back of the engine. It allows tipping or rotating the
engine to any angle during assembly. Click here
to see a picture of this engine stand.
6/18/00 I
have prototyped a printed circuit board that is capable of audibly
indicating when the ignition points are open or closed in any small
engine that uses a conventional magneto. When an ohmmeter or buzzer is
used to indicate if the points are open or closed, the low resistance of
the magneto primary winding that is connected across the points obscures
the reading and must be disconnected temporally. This circuit board
ignores the coil primary so it can simply be clipped on the ignition
switch or "kill" wire. Removal of the flywheel is unnecessary
for verification of timing. I am unsure at this time if I will market
this tool. The cost in kit form with a circuit board, all parts, test
leads, instructions, and a case would be in the vicinity of
$30.00-$35.00. It will require soldering. If you have an interest
in this tool please send me an email.
12/16/00 Bill Bruce, one of my web
visitors, was trying to work his side plate with the neoprene seal in it
over the crankshaft in a Cast Iron Cushman engine. He noted that it was
very difficult to work the seal onto the larger diameter area it seats
on without damaging the seal and suggested the possibility of making
some kind of fixture to facilitate the job. With that inspiration,
I made a bushing, tapered on one end, square on the other, that
can be slipped into the neoprene seal. Using this bushing one can simply
slide the side plate onto the engine and the seal drops right in place
with no effort and no damage. I will be placing a drawing of this
device at the tools page soon. If you have need for one before I
do that just email for more information.
Additional Information on Main Bearings and Races
When
I wrote the manual I assumed that bearing and race replacements would be
deferred to a machine shop. I assumed incorrectly, because I have
received requests for more information in this area. If the
bearings and races are smooth and rust free they can be reused. If
the bearings are rusty, pitted or have any other obvious defects they
should be replaced. The races should be very smooth, with no rusting or
pitting. A rough or pitted race can wear out a new bearing quickly, so
replace them if in doubt. Both cones and races are available at
low cost from any Cushman dealer. Removing the main bearings from the
crankshaft requires a special tool made for the purpose. The use of any
other gear puller may result in a bent crankshaft. The tool is
available from Carpenter 1 as part number TOOL-5 . Elbert
Faris2 makes this tool for Carpenter and he can also replace bearings
and repair damaged crankshafts and flywheels 2. The tool has
a special retainer that clamps over the bearing and pulls it off of the
shaft. A separate accessory, TOOL6, is also available for
pulling the crankshaft gear, but the gear seldom requires
replacement. The bearing is replaced by pressing it on the
crankshaft while hot. Before doing so, smooth the crankshaft with
very fine wet or dry sandpaper to remove any rough or rusty spots. Clean
the bearing in a solvent to remove all the protective oil or grease.
Heat the bearing to about 400 degrees in an oven and quickly press it on
the crankshaft. Never press against the opposite end of the crankshaft
or it might distort it. Position a press plate so that you can press
against the back side of the counterweight. Make an arbor out of a
length of pipe of the correct size to just fit over the end of the
crankshaft to press the bearing back on. Do not press against the
rollers or the bearing may be damaged. As soon as the bearing has
been installed lubricate it with motor oil to prevent rusting. The
races are driven out of the side plate and the block with a drive punch.
First remove the old oil seal if you have not already done so. On the
later side plate that uses the neoprene seal you will see two recesses, one on each side. Carefully
position a drive punch in these recesses and drive the race out of the
side plate This newer side plate does not use an oil retainer washer.
(For the following cone removal see the update posted on 6/15/00) If you have the
older felt seal type side plate you will have
an oil retainer washer that has to be driven out with the race. On the block, an oil retainer washer is
always used and it must also be
driven out with the race. The oil retainers will be destroyed and will
have to be replaced. The new races are pressed back in with an arbor,
Cushman part number 876674 If
there is interest I will provide CAD drawings for some of these
additional tools.
Note on Installing Valve Guides
When installing new valve
guides, if you do not have the correct arbor use a 5/16 bolt that is
long enough to index down in the valve guide bosses below the oil
chamber to help center the assembly while pressing or driving the guide
in. Note on Installing the Oil Pan
I recently heard a
horror story from an experienced engine mechanic about the silicone
sealant squeezing off inside the crankcase and jamming the oil
pump. In view of this potential problem I think it may be best to
avoid the use of the silicone material altogether. Permatex 300 is a
good sealant to use. It is described on page 14 of the Manual and comes
in a small can with a brush in the cap that makes it very easy to
apply. You can also put a little on the screw threads to keep them
from weeping oil. I am told that Hondabond, Yamabond, or Halomar, all
aircraft grade sealants, are superior to the Permatex line. I have not
tried them. Notes on Oil
Pumps
There were at least three different style oil pumps used in the two
piece Cushman engines. The first was used with crankshaft 82-5 and 86-5
(Varimatic drive) and has a curled circle at the end of the delivery
tube. The second has a delivery tube that is slightly curved. Both of
these pumps have the second spring and ball in a vertical
configuration. The third pump is the one pictured in the manual
and has the second spring and ball at an angle. The first model
must never be used only with the older 82 series crankshafts, the second
and third are fine for the later 92-5 crankshaft. This is from a Cushman
engineering bulletin dated January 8, 1952. Note
on Connecting Rod Centering in Piston
One engine rebuilder found that his connecting rod was not centered on the
piston pin when the engine was reassembled. The exact cause could not be determined, but it may be
related to replacement bearings and/or races holding the crankshaft out
a little farther than the originals. In this instance the cure was to
remove the spacer behind the crankshaft bearing on the magneto side and
mill off .025. This also required that the the shim thickness
under the side plate be reduced by the same amount. Only a very observant
person would likely notice this off-center condition, so it may be common
in Cushman engines.
Tip for sealing the side plates:
Here is an easy way to seal the side plate and shims on the Cast Iron
engine:
I use a light coat of aluminum paint on all gasket surfaces. I paint the
shims (both sides), block and the side plate gasket surfaces with
aluminum spray paint prior to adjusting the crankshaft endplay. This way
the endplay doesn't change when you make the final assembly of your
engine. The paint is soft enough to bond together and seal the engine
and as an added bonus, it is easy to disassemble when the time comes.
Hope this helps.
Ross Murphy from Cushmannet Errata:
Manual page 2 Paragraph 2. The Flywheel nut is 15/16, not 1-1/16.
Page 12 under the oil pump exploded view, second sentence, eighth word,
"tap" should
read "plug"
Footnotes:
1. Dennis Carpenter Cushman Reproductions (704)
728-1237
2. Elbert Faris (561) 794-4559
3. Tommy Goode, 47B Laura Lane, Bastrop, Texas 78602 Phone (512)
303-0224 |
