I have been examining a Poulan 18cc weedie motor for possible conversion. I have read here that the motor itself is low on power. Just looking at it, I can see a couple of reasons why. Both the intake and exhaust ports are pretty small. However, it has some good points too. The opening for the intake is more than large enough and it tapers down to the opening in the cylinder. It can take a much bigger carb if the port opening itself can be opened up. Same goes for the exhaust. The opening for the exhaust is huge. The transfer ports also seem to be plenty big enough. The crankcase can be carved down to a nice size and is very light. There is plenty of space on the crankcase to mount a sensor for electronic ignition. And finally, the piston ring is pinned. The gasket for the cylinder is very thick also. Seems that compression could be increased by eliminating the gasket and using RTV to seal.

Now to my questions. How would I go about opening up the intake Cand exhaust ports. Looking at the cylinder, looks like the best way would be to grind down on the intake port and up on the exhaust port. This would keep the timing the same for when these ports close. However, this will increase the timing on when they open. Here is my question. How will that affect how it runs? I cant see how this would change much except to allow more fuel in on the intake side. But it could cause a loss of power on the exhaust side if the exhaust opens too much. Am I right in this? If so, what is the limiting factor? Last question, what tool would I use to make these changes? I have a dremel tool. Can I use a grinding bit in my dremel to do this?

I would like to make this motor powerful enough to fly a .60 size warbird. I have a set of plans for a Zero. With the short nose on the Zero, I am sure it could use the extra weight up front if I can get enough horses out of it.

Thanks
Jim