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    Flywheel       Spark Plug    Magneto    Brakes      Electrical      Front End     

    Oil       Tires     Gasoline    Drive Belt    Engine    Alignment    Clutch  

If you do not find the information you need on this page be sure to check the Hints & Tips Page.  The Site Search link can be used to find every occurrence of any word or words at this web site. The Site Search is very powerful and can help you find information contained in the technical and historic articles.

Be sure to also see the article on Vanguard Engine Conversions.


How do I get the flywheel off?  On a Cushman Husky or Silver Eagle engine the flywheel is removed by striking the end of the crankshaft with a ball peen hammer.  Before doing this you must remove the flywheel nut and lock washer.  If this nut was installed to the old Cushman specification it was tightened to 70 foot-pounds.  It is going to take considerably more than that to get it off. The best way to remove the nut is to use a ½ or larger breaker bar and a 1-1/16 socket that is deep enough to clear the fins.  While someone else holds the flywheel by it’s perimeter carefully strike the end of the breaker bar with a wood mallet. One or two blows should loosen the nut.  Do not attempt keep the shaft from turning by jamming any part of the flywheel or clutch with a crowbar or similar object. After the nut and lock washer have been removed, screw a knockoff tool on the end of the crankshaft threads, part number 112015 for the OMC engine or 809315 for the Cast Iron engine. The knockoff tool is designed to prevent any damage to the crankshaft threads. If you attempt to remove the flywheel without it or try to substitute a nut for the tool you may damage the crankshaft.  Tap the tool lightly while tightening it to be sure it is seated as far down as it will go.  It will help if you have a second person to put a little outward force it on the flywheel.  Now strike the knockoff tool smartly and squarely with a large ball peen hammer and the flywheel should pop loose. If it does not come loose with the first strike be sure that the knockoff tool is still very tight on the shaft before trying again.  Be very careful when you do this because if you strike a fin it will break off.  When you are ready to reinstall the flywheel first tighten the nut as far as you can with the breaker bar while your helper holds the flywheel by its perimeter. You can torque it to about 25 foot-pounds or more this way. The best way to tighten it the rest of the way is to purchase a strap wrench that can hold the flywheel around its perimeter. One person holds the strap wrench, the other torques the nut to about 60 Ft/Lbs. The original Cushman method is to strike the end of the breaker bar lightly with the hammer to tighten the nut a little more. If you do it this way you just have to use your best judgment and shoot for about 50 to 60 foot-pounds.  A couple good strikes should do the job.  Do not over do it because over tightening the nut may cause the flywheel to crack. Also be very careful with the mallet because you do not want to loose a helper or break off a flywheel fin.

What Spark Plug should I use?   Most references state that a Champion #7 spark plug was used for 1948 and earlier scooters. However, the Cushman manual for the model 32 and 34 published in 1943 states that the correct plug is a Champion 6M. A suitable substitute for either is the Champion D-16 and this is also the correct plug for all later engines that do not have a tapered seat.  Heads with tapered seats used a Champion F14Y, which is no longer made but some Cushman dealers may still have a few in stock. A Champion RF14Y or RF14YC is an acceptable substitute and is readily available, but it is a resistor plug.  Other plugs often recommended for the tapered seat head are the Bosch 6200, Champion 4011, NGK WR5, Champion 870 and Autolite 46. You should make your own determination as to the suitability of any of these alternate plugs. Be sure not to put a tapered seat plug in your non-tapered seat head or it will likely be ruined.  I gap all plugs at .026. Cushman gave various recommendations for gaps over the years, .027 to .030 for the 6M, .030 to .033 for the #7, and .026 for the F14Y.  If you have excessive fouling problems you can go to a higher heat range plug.  A higher number plug is hotter and a lower number is colder.   Many of the hopped up engines work best with a colder plug.

How can I tell if my Magneto is OK?  Obtain a test spark plug like the Tool 4 sold by Cushman dealers. This special plug has a clip welded to the grounded side that you can attach to any convenient grounded object. It has a much wider gap than your regular plug.  Find a location out of full sun, connect the spark plug wire to the test plug and kick the engine over normally. You should see an intense blue spark. If your magneto does not have sufficient voltage to jump the gap on the test plug it will not jump the gap on your regular plug satisfactorily when the engine is under compression.  A weak magneto will cause the engine to be very hard to start and may cause it to cut out as you open the throttle. It will also cause spark plug fouling.  Here is a tip that will help you. If you try to start your engine and it is very hard to start and seems to fire or backfire a lot, the most likely cause is either a weak magneto coil, a fouled spark plug, or oxidized or dirty points. It takes much more voltage to jump the gap when the spark plug is under compression so if it tends to cut out when you accelerate most likely have an ignition problem. Since the Cushman engine fires every rotation of the crank and the compression stroke occurs every other rotation, the unspent gas charge will often ignite during the exhaust stroke when the plug is easy to fire. This gives the impression that the engine is trying to start. When an engine is running normally the extra spark has no effect on its operation.

How do I Adjust my Brakes?   Your brake shoes can be centered by first loosening the centering cam directly opposite the actuating cam.  Have a second person hold the brake petal down tightly to force the shoes to center.  While the person continues to hold the brake tighten the cam nut securely. Grabbing brakes can be caused by a loose brake plate screw, a loose centering bolt,  or a worn bushing on the actuating cam  

How do identify my Electrical System?   The very earliest Cushman Scooters used a separate 6 volt AC generator that was run by a belt.  About 1948 they put lighting coils inside the flywheel and called it a Permalite. The earliest of these Permalite systems consisted of two very large coils in parallel that supplied six volts for the headlight and taillight. Cushman apparently had complaints about the lights burning out too quickly and they reduced the size of the coils by about 1/3. One reason that the early lights burned out was because the dimmer switch took the headlight out of the circuit too long when it was changed from low to high beam. While the headlight was momentarily out of the circuit the taillight would occasionally blow from over voltage. With the taillight blown the headlight would follow shortly because it now had too much voltage. There is no voltage or current limiting of any sort in this early system and the voltage delivered to the lights is pretty much a function of the lamp load and how fast the engine is running. The lights are very poor at an idle, more so for the later small coils. In 1959 Cushman went to a greatly improved 12-volt system that featured two coils in parallel for the headlight, a separate coil the taillight, and another separate one for the newly added stoplight. The three separate lighting leads exiting the flywheel plate can identify this system. This system also uses an elementary form of current limiting and it works very well. See the technical section in this web site for more information on electrical systems.
Watch that front end!  If you acquire a new scooter check out the front end before you go for a ride.  On a Springer eagle check the bushings on the front suspension spring arms for excessive play. On a tubular fork model check to be sure the bushings inside the lower section are not worn excessively. Either of the above can cause the front end to go into an uncontrollable oscillation.  Also be sure that the fork bushings are tight and that fork will turn smoothly from limit to limit.  Springer Eagles and many other models use bushings.  The tubular fork models use ball bearings top and bottom with felt washers for grease seals.

How often to change oil  
Cushman Scooters have no oil filter and the oil should be changed very often. Oil is very inexpensive when compared to engine damage.  Under normal conditions I like to change my oil about every 250 miles although this may be a little too often. On a new rebuild I change the oil the first time after one hour of operation. I am not going to go into what kind of oil to use because there are so many strong opinions on the subject.  I use straight 30 weight detergent oil made by any major manufacturer that meets SG specifications. This is surely superior to any oil known when Cushman Scooters were manufactured. Note: it is very hard to find oil that meets the SG specification and there is some question about whether the newer classifications like SJ are suitable for air cooled engines. I have found that Havoline makes a straight 30 weight oil that meets both SG and the diesel classification CD and it should be ideal for our Cushman scooters.

How do I Make Sure my Chain and Tires Run True?  You should check your tires to be sure they are in alignment. This is easily done with a piece of string. Tie the string to one front axle bolt, run it forward around the tire and back to the rear of the rear tire. Have a second person to hold the fork straight ahead while you do this. Now pull the string very tight and have the person holding the fork turn it back and forth slightly until the string just touches the back of the front tire as it passes by.  You may have to adjust the string down further on the tire to avoid obstructions and you may have to block the wheel to keep it from turning. As the string just comes in contact with the back of the front tire the string should also be touching the front and rear of the rear tire equally. If it is not, adjust the rear axle and try again.  Now, if your frame is straight, your transmission is in exact alignment, and you are just plain lucky your sprockets will also be in perfect alignment. This is easily checked with a piece of 1/8 x 1 inch aluminum flat bar. You will have to trim parts of the flat bar to avoid interference with the frame.  Cut it the right length to reach from the axle nut to the far side of the smaller sprocket.  Now hold the bar against the sprockets and see if they are in alignment.  If not you may find that your transmission is out of line or that your frame is bent.  If you are lucky enough to have them in alignment you are done, and you will know in the future that when your sprockets are in alignment that your wheels are also in alignment. The aluminum bar makes very easy to verify the alignment after chain adjustment. The best way I have found to tighten the chain is to first loosen the bolt that retains the brake shield, then loosen the two axle nuts just part way. Use a block of wood against the nut and gently tap it back with a wood mallet.  If your nut tension is just right the axle will move easily and retain the new position. Move both nuts equally and recheck for alignment with your aluminum bar before tightening. You will be amazed at how little you have to move the axle to tighten up a loose chain.  Many Cushman hubs are not entirely concentric. You should always rotate the rear wheel and check the tightness of the chain as the rear sprocket goes around. You may find one spot that is much tighter than any other and if so this must be the point at which you adjust the amount of slack in the chain.  Failure to do this can cause the chain to become extremely tight at that point and cause excessive wear. The Machinery Handbook says that a chain should have a little bit of slack but that too much is very harmful. I suggest a free vertical movement of about 1/2 to 5/8 of an inch midway between the sprockets. A new chain will stretch quite a bit at first so check it often. When installing the master link always orient the keeper with the open end trailing so that an obstruction cannot knock it off

What is the Best Gasoline to Use?  All Cushman engines are low compression and will run just fine with 87-octane gas.   Because we sometimes do not run our scooters for an extended time the quality and stability of the gas is more important than the octane.  I have used gasoline that turned dark and smelled stale after no more than four to six months.  I have also observed that Amoco 93 octane will stay crystal clear and appears quite fresh after twice that long or even longer and this is my gas of choice. If I am forced to use another brand while on the road I will drain it and replace it with Amoco before parking it.  For extended storage I add a fuel stabilizer. If I am not going to ride the scooter for a month or more  I shut off the fuel and run the carburetor dry.  I do not recommend emptying the gas tank.  Unless it has been sealed it will tend to rust when it is empty, at least  in humid Florida.  If you have problems with your spark plug fouling mixing 20 percent 100LL aviation gas or racing gas with 80 percent Amoco 93. You will be surprised at how much cleaner your engine will be.

How tight should my primary drive belt be? In a word, it should be as slack as possible and still not slip. When you over tighten the belt you put a unnecessary lateral force on both the engine, clutch, and transmission bearings. You also increase rolling friction. Cushman used roller bearings in the clutch that is designed for use with a belt and just bronze bushings in the ones designed for a primary chain drive where there is much less lateral force acting on the bearings. Sometimes the clear liquid belt dressing sold by NAPA stores and others can be used to prevent the belt from slipping and avoid an excessively tight belt. A high quality serrated belt may also slip less. Be sure that you do not buy one of the cheap belts designed for fans and small appliances.

How Can I Get More Horsepower out of my Engine?  Most 2-7/8 5 HP engines used in the Eagles can be bored out to 3 inches to give about 8/10 of one horsepower more. Before you do this you should give it some serious consideration. The added power sounds nice, and it usually works out fine, but there are reports of blocks cracking. Unless you are an expert and know how to center the bore in the engine block you should not attempt it. You can get far more increase in performance from the 2-7/8 inch engine by replacing the old lower lift cam that only the 2-7/8 inch engine used. Replacing the cam with the newer higher lift cam will increase its power to about 7.2 HP. Mill the head about .030, and using a thin “performance” head gasket it should produce well over 8 HP.  If you want even more performance just put in a Rocket or similar high performance cam and perhaps an oversize intake valve. If you install one of the extremely high lift cams like the Rocket you must check to be sure that there is adequate clearance between the top of the valve to the head and if not must be milled out directly above the valve the absolute minimum necessary to provide clearance. The spark plug will also have to be selected by trial and error to find one that seats with the electrode projection facing away from the large valve. The spark plug can never be removed or installed unless the valves are seated because as the plug is screwed in the electrode will hit the valve. An alternate is to fill in the existing spark plug hole and drill a new hole a fraction of an inch farther to the rear and tap it for a modern spark plug with a smaller threads. These modifications are not for the inexperienced, but any good engine shop should be able to do the work for you. Most shops get really excited about working on a Cushman engine.

How much tire pressure should I use.   Here is another area where there is a large disagreement about what is correct.  Most Cushman tires are rated for about 30 to 32 pounds per square inch of pressure so you should never exceed this.  Many knowledgeable people feel that perhaps 26 to 28 pounds is about right. If you are carrying a passenger you should use the full 30 to 32 pounds.  Higher tire pressures mean less rolling friction so you fast guys will want the maximum.  Check them often because they are famous for leaking down. A low front tire will cause instability when turning and may lead to an accident.

How About Larger Tires?  There are a wide selection of 10 and 12-inch motorcycle type tires available and in general they are much safer than Cushman tires because they are rated for higher speed operation.  The 10 or 12-inch figure just gives the rim size and there is a wide variation between the diameters of the tire used on these rims.  Some of the 10-inch tires are very little larger in diameter than the Cushman tires and they will fit nicely in the front fork and under the rear fender.  12-inch tires may require modifications including fork extenders and are recommended for experienced persons only.

How do I repair a Disc Clutch?  The Disc Clutch used by Cushman is very reliable but it may need new linings or replacement bushings.  I have reproduced a Cushman Technical Bulletin on this subject issued in February, 1959 that is very comprehensive. It is too long to present on this page so please click the link to view the information.

Can I put Electric Start on my Cast Iron Eagle?

Two manufacturers make kits to go on the Eagle to allow electric starting of the engine. Dennis Carpenter Industries makes one that mounts on the floorboard and has a belt that goes to the clutch pulley. Most of the vintage Cushman dealers sell this starter. It has a unique small pulley that completely disengages the drive belt after starting. I have used two of these kits. One was put on a 1953 eagle and it works pretty well, except that the starter often stalls and requires that you turn the key off and back on. It does always manage to start the engine. The other was on a highly hopped up high compression 8 Hp engine and it could not start it reliably and it was removed. There are versions for the Eagles with the flat floor pan and for the Eagles with the raised floor pan. Carpenter suggest removing the kick starter on the raised floor pan model, but if you are very careful it can be left in place to be used in an emergency.  It takes a very careful controlled kick because the starter lever bottoms against the starter motor. Using these starters requires that you charge the battery fully before riding or that you modify the lighting system to provide a small charging current to the battery. You can find more information on this at this web site. Check the Technical Index or use the Site Search.  The other is a starter-generator combination kit marketed by Nevil Swigart and is much like what is used on a gasoline golf cart. It mounts behind and below the seat and has a belt down to the clutch pulley. It stays engaged at all times and provides a significant charging current for the battery after the engine starts.
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