Here, http://www.youtube.com/watch?v=noH_SOBe0YE can be seen the case reed version of the Tanaka 26cc.

The stock cylinder had the head milled off and a new head button was made that is secured with long bolts that also holds the cylinder down. The head button carries an OS Turbo Plug.

The stock intake port has been plugged and a new, reed intake assembly has been installed to the bottom of the crankcase.

The carb is from a K&B .40 Sportster with a venturi bore of .34" as opposed to the stock bore of .45"

On the baseline, 18 X 6 Zinger wood prop, we are getting a solid, 7500 RPM. That translates into an extra .4 horsepower over the stock gasser on ignition.

We have shed nearly two pounds of ignition gear and gained power at the same time. Can't beat that.

However, we likely would gain that and more, if we could increase the compression ratio on the stock gasser. The real payoff with this conversion is the weight reduction.

Unfortunately, throttling didn't exist. Anything less than 3/4 throttle produced a flameout.

Flipping the engine to a sidemount configuration cured that, interestingly enough. We are speculating that at low throttle, engine suction was insufficient to draw fuel properly. Sidemounting provides for much easier fuel flow to the bypasses for delivery to the cylinder.

The plug is a P8, OS turbo plug. This is their cold plug and was tried in this case, simply because that's what we had on hand.

The head button was made to give us a compression ratio of 14:1 and this has proven to be about right. Decreasing the compression as an experiment will be tried but we don't anticipate any benefits. The runs today don't exhibit any overcompressed symptoms. More productive will be increasing compression to the point of getting some ping. Then we'll back off a bit and proceed to experiment with a bit of nitro (2-5%) along with various plug heat ranges and extra shims.

Pictured is the installation of an Enya, three needle throttle from their .60 which has a bore in the barrel slightly larger than the stock Walbro.

Throttling still wasn't perfect as we couldn't get less than 3K. The stock, ignition engine on gas gave a forever, solid idle of 1.3K So, as a side mount improved throttling, we reasoned that inverted might be even better. Unfortunately, it was pretty much the same as side mount.

Either the reed design itself isn't suited to this configuration, or a reed on the case just isn't a good idea.

Next up will be to install the reed assembly onto the sideport as per the stock arrangement.