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"

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