On the mylar reed. Some folks when we would race, would swear by the 0.10" mylar reed. Others 0.012" in the same material.

Personally, I've observed some deformation on the .010" reed after a few runs. Enough to not seal at low speeds and make starting a genuine P.I.T.A. The 0.12" version while costing a couple of hundred RPM's didn't seem to deform. Can't remember why the 0.012" mylar reeds didn't make it to production.

Personally, and off company time, I fabricated reeds out of teflon. Same basic performance, same basic dimensions. Now days, making a reed would mean careful work with an exacto. We had a hand operated die. Very similar to a modern day whole punch, only shaped like the reed. Some material, a cutting board, and a quick tap of the hammer would net you one reed.

The plastic/teflon reeds will not have the naturally sealing arc of their metal cousins. All this affects is starting if your not vigorous enough.

Here is another tip. The reed sides have curved cutaway points. The closer to the actual seal you make these cutaways, the faster your engine. But the sooner the reed gets tired. You'll have to experiment...Suggestion, go with a three point contact on the reeds for retention, instead of the factory four. Going with two, and you'll suck the reed every time. Been there, done that.

And on the reed retaining spring, re-arc it and give the reed another 0.015" of room to move in toward the crankcase. Start with 0.010 of extra room and move up from there. If you suck a reed, you've gone too far.

To increase crankcase pressure (slightly), reduce the c'case volume by eliminating the thin gasket between the tank and the c'case. Seal with a high quality, high temp automotive silicone. Anything else and the fuel will attack it. You can also use the newer sealant called "The Right Stuff" available at automotive stores. affectionately called the "black death". It's called that because if you get it on your clothes, nothing will take it out, following by your wife killing you for ruined clothes....:-)

In either case of the silicone or the black death....Allow it to cure overnight at room temperatures, or the sealant will be dislodged in the first run. remember, there is not a lot of seating area..... And don't slobber a lot on the insides, or it'll squeeze out onto the reed rendering it useless. Better to have a tad excess on the outside than on the inside.....

Another trick when we wanted longer run times, was to drill a hole in the tank, and run fuel line from the internal nipple, to an externally mounted tank. Distance is critical. Keep it close.

If you go with the plastic/teflon reeds, the urge will be to use an electric starter. I can't tell you how many engines came back to us "in warranty" with the front of the c'case ground off from an electric starter. Aluminum upon aluminum does not make for a good bushing material.

To convert for electric start: Measure the front prop hub to c'case clearance. If it's not 0.010" or greater, you're going to have to grind on the c'case to create clearance. Get some hobby sheet brass in about 0.010" thickness, drill a hole the size of the crankcshaft and fabricate your external radius. PLace this "shim" between the c'case and prop hub and re-press. Seat the prop hub completely. If it does not spin freely, you need to remove more material from the front of the c'case. Once proper clearance is achieved, (just enough to spin freely, or about 0.0015").....then just add fuel to this "bushing" before each start for lubrication. You'll not eat up the prop hub nor the c'case.


Dave............