Once the metal jacket strip was tight against the block, I put the block in our oven in the kitchen for 10 minutes at 250 degrees. (Do this while your wife is away for the day) When I removed the block from the oven, I started to weld on top of the block, from the intake side, to the exhaust side of the block I used Stainless welding rod with my arc welder. I tried welding rod made for cast iron, but the stainless proved to be the best.. When you start to weld the jacket, you welded as fast as possible before the block lost its oven heat. If you did not preheat the block, you could, and often did crack some of the fins. Once the main jacket was welded on the hard part began; now you had to make small pieces to fit into the areas not covered by the bigger jacket. It normally took the better part of a day to prepare the pieces needed and to weld up a water jacket on a motor. I wish I could tell you that the water cooled Cushman was the best. It was in many ways the best for me, but there were several air cooled Cushman engines from North Carolina and California that I was never able to outrun. The builders of these engines were Frank Jarrell, of Kemersville, N.C., and Frank Kiler of Visalia, Ca.

 Now that we have pretty well run through making a water cooled block, I will mention some of the other things that help make this motor stay together and run better. The crankshaft on a Cushman engine is way out of balance. When I first tried to balance the crankshaft I drilled holes in the counter weights, packed the holes with lead, and welded a steel plug to cover the holes. A lot of work, and I never could get enough lead into the crank to bring it into balance. I finally welded a steel plate much like you can buy today on the counter weight. Since we never had the cranks ground to under size, welding this in place worked the best for us. The plate was cut from 1/4 inch steel and was a bit larger than the stock Cushman. The rod, while being one of the strong points of the motor, had a weakness in the area of the 4-rod bolts. The straight cut where the head of the rod bolts were left a shear point where the rod almost always broke. We brazed this area and filled it with brass, covering the head of the rod bolts and then shaping it to give it a rounded appearance. This cut down on the broken rods a great deal. I normally changed rods every month, five each racing season, as a mater of good maintenance. The crankshaft bearing spacing was a weak point, in that they are so far apart and allow the crankshaft to flex near the rod journal, which leads to it breaking at that point. I did break several crankshafts early in my racing career, one time it destroyed the block and camshaft. I learned early in my racing to change the crankshaft every month to 6 weeks. Here again, just good maintenance. On one of the motors the crank broke and the connecting rod hit and bent the camshaft. I put this camshaft in a press to straighten it and for some reason it became one of my best. It was only in later years that I understood that bending it and then pressing it back straight changed the lobe centers. For some reason this cam made a motor run like the "Bat out of you know where." Previously in this article I gave you the degrees for the cams made by Bob Sawyer. Almost all the cams I bought from Bob would give you between.280 to.300 valve lift. Here again, some people would like to lift the valves to the moon, but you can only flow so much thru a valve, and this amount of lift proved to work well. I once took a cam blank to Iskenderian's in California to get a change in the grind. This was not the main Ed Iskenderian shop that everyone knows about, but his brother Luther who had a shop behind the main building where he did motorcycle cams. He was so excited when I told him it was a cam for a Cushman. He said he had driven a Cushman Airborne all over the Philippines when he was in the service in WW2. When I told him the size of the valves, and the valve spring seat pressure of 80 pounds he was honest with me and said I had a good cam for what I wanted to do with the cam grinds made by Bob Sawyer. I did, on several occasions, machine my own cam blanks on my lathe and had the cams ground by Effingham Cam Grinders in Effingham, Illinois.

When I went to the water-cooled motor, piston seizing was a thing of the past as the motor ran so much cooler now. We replaced the piston clips with Teflon buttons. The clips had a tendency to crystallize and break, in doing so destroy the cylinder wall. We reamed the piston so that the wrist pin floated back and forth, with the Teflon buttons pressed in each side contacting the cylinder wall. Cushman did this early on with some of their first motors, except they used aluminum plugs, or buttons as we call them.

To set the end gap for a ring place down it in the bore of the motor and, with a feeler gauge, find how much gap you have. To increase the gap place a fine file straight up in your bench vice and, with a side of the ring in each hand, place the ring with a side on each side of the file, and hold the ring ends tight against the file and draw the ring up and down on the file. This way you take a equal amount off of each end of the ring. Keep putting the ring back in the bore of the motor and checking with the feeler gauge so that you do not open the gap too much. When you have done this with all three rings, place them on the piston. Cushman, in all their literature, fails to tell you where to place ring on the piston after you gap it. Gap the rings on the side of the cylinder opposite the intake and exhaust. The bottom ring should be set so that the gap is straight across the piston from exhaust valve. The 2nd ring gap is across the piston from the intake valve and set the top ring is gap across the piston in line with the exhaust valve. With the rotation of the motor, and rod angle, this allows the rings to maintain the gap you have set, even close this gap a bit on the power stroke. The spark plug we used was Champion 14 mm J series. The J series was a marine plug that gave a number of heat ranges to work with, Most of the time we used a J2 or J4 for a hot day, or a J6 for a normal day, or cool evening. A good spark plug with methanol fuel was a must.

Now that I have explained as best I could about the Water Cooled Cushman, I hope the things we have discussed will give you a few things you can use on building your next scooter motor. I know some of what we talked about may sound strange to some, and some will think I don't know what I am talking about (they still think the world is flat but these are things that worked well for me, I am just passing them on to you.)

I have just finished restoration of my 1960 Standard Eagle in the last 3 months. I put the motor together with lash caps on the lifters, and Wisconsin valves and heavy valve springs. The Wisconsin valves gave me longer valve stems to work with, which gave me a better choice of valve springs. The cam is a stock Cushman that I ground a new profile on. When I put a degree wheel on this motor, I got what I was trying to accomplish, a split over lap. The intake opens 77 degrees before top dead center and closes 35 degrees after bottom dead center. The exhaust opens at 77 degrees before bottom dead center and closes 35 degrees after top dead center.  Intake valve lift is .282 and exhaust is .280.

Photo of Bob's Test Stand

 I am just breaking the motor in so I have not opened it up yet, but I am sure this motor will run well. I got so tired years ago of mounting a motor on a newly painted scooter, and then having to take it off for some reason and damaging the paint in the process so built the motor break in stand that you see in the picture. I have an attachment that bolts where the gray motor block is shown for polishing aluminum racing wheels. That is why the 3/4 electric motor is installed. I also have a 2 HP electric motor that I bolt in place of the 3/4 HP when I break in a Cushman motor. I can start the Cushman and leave it running on the stand, or I can remove the spark plug wire and put it on a second plug laying alongside the motor and allow the electric motor to turn the Cushman. Since the motor turns 1140 RPM it is just right to run the engine for an hour or two to make sure the rod bearing fit is right, and I can also check the output of the magneto lighting coils at that time. After an hour or two with the electric motor I fire up the Cushman, regulate the RPM’s, and run it until it comes up to operating temperature (or until my neighbor has had enough). Then I may run it again the next day for the same amount of time. When I put it on the scooter it has time on it and I know it is going to run like I planned.

 I wish all of you the very best, and keep those Cushman Scooters running

Your California Cushman Friend Bob Jungbluth

Bob raced the Cushman engine for many years and set many records. His need for engine parts resulted in frequent visits to the scrap yard in Lincoln, NE to pickup parts that the Cushman Motor Company was discarding. The parts he salvaged helped save the Cushman Scooter. I thank Bob very much for writing this article for the web site. -Ed