Piston Rings: Perfect Circle 71148, Hastings 278. Oversize available through 0.050” on special order.
Gas cap: NAPA 7031020 fits but does not have the oil measuring cup attached as does the original. Use only the NAPA cap, do not substitute with another brand.
Kick starter return spring: Garner 1112270135-MR. A turn must be removed, ends torched to soften and hooks formed at ends. These springs do not fit all the kick starters as some of them have a larger diameter “bushing” extending from the rear of the starter.
Carburetor: The 1948 Martin “40” outboard engines used a Carter carburetor which can be modified to work with the Dynacycle engine. Venturi size is correct (23/32”), fuel mixture adjustment comes out the bottom.
Needle bearing MUST be installed by pressing from the imprint side. Apply grease to the outer shell before installing.
I have several unfinished pistons available. OD requires machining to match your overbore, ring groove cut and ring anti-rotation pin installed. Wrist pin bore already machined. New wrist pin and clips are available for an additional $4.50. These are PREMIUM quality, cost me a kings' ransom, but I have more than I will ever need $35 each. Also a few finished stock bore and 0.010” oversize $75 each.
I urge Dynacycle owners to use Amsoil Sabre Pro oil, 40:1 ratio. It burns clean, sparkplug fouling minimized.
The intake reed is prone to pitting and cracking which seriously affects starting and performance. I have the 12 mil spring steel material available at no charge or will make the reed to $8. There are two versions available; one with a single attachment screw, the later engines using two screws. If you want me to make a replacement, let me know which version you have.
Air cleaner: Walbro CAA-4H. This is a nylon-cased filter that fits and functions very well. Replacement element (foam rubber): Walbro 125-15.
If your lower connecting rod needles are pitted (28 pieces), try cracking open a B-1612 needle bearing for replacements. The nipples at the ends of these needles may require moderate buffing to remove sharp edges, if present.
Muffler shell can be replicated by using 2-1/4” exhaust pipe, ~18” length with the one end “belled down” to ~1-1/4 diameter hole (production units were inconsistent. I have measured everything from 1-1/8” to 1-7/8”). Sixteen guage is preferred, however it is difficult to locate. Your muffler shop has the equipment to do this. Muffler insert: Patriot H2971. Some of these inserts have a cap at the far end which will require removal prior to slipping into the muffler shell. I have drawings of the two pieces that attach to the exhaust pipe (nose cone and nut). Email me for copies at firstname.lastname@example.org.
Early production Dynacycles did not have a fuel filter installed. It is imperative that one be placed in the fuel line to keep debris out of the carburetor. See Service Bulletins.
The clip securing the kick starter to its shaft is prone to coming off. Consider drilling and tapping a 1/4-20 hole in the end of the shaft; install a bolt and large diameter washer (1” minimum).
If your engine is not equipped with the lighting feature, consider replacing the ignition points with a solid-state module. Timing position is the same as with the point configuration. Suggested installation pictures available upon request.
After sixty-one years of riding Dynacycle, I have learned the wisdom of always carrying a spare spark plug and removal tool. You can't drive a single cylinder engine with a fouled plug!
Dynacycle issued a Service Bulletin and provided a part for attachment to the bottom of the kick stand. The stock kick stand has an extremely small footprint, whichh can penetrate into warm asphalt or any soft ground – causing the machine to tip. This, in turn, may cause the carburetor float to lose control allowing the fuel tank to drain. Upgrade part consisted of a 1” X 2-1/4” oval plate with a 5/16” rod welded to it. After removal of the tang at the bottom of the stock kick stand, the rod was slipped into the bottom and welded into place.