Originally Posted by elacruze
My expertise is in much larger engines, but I have to ask about the noise...is it mechanical, or intake/exhaust roar? On engines with very small cylinders, the valve lash can make an enormous difference in performance. Check the lash, check the spec and if you find that the lash is on the loose side or looser than spec, try tightening it to the tight side of spec. If the main jet in the carb is replaceable, go up one size and retest. if it's not replaceable, consider the cost of a new carb and decide whether or not to drill out to the next size (you sound capable of using good science). Unless the engine is truly not engineered to produce 6, then only a few things can restrict the power that badly. Do the spark plugs have any color at all? If not, certainly you can benefit powerwise by adding some fuel. I know how manufacturers are fast and loose with power numbers, but 50% off sounds like some sort of restriction.
Here's a good one-I had a motorcycle once I thought too slow, and checked everything. A friend of mine, called in frustration found that the throttle wasn't being pulled open all the way. Check to see that you're not working with 2/3 open carburetor.
i don't think it is exhaust as that comes out underwater through the prop. To be honest im not sure.
I am not going to adjust internal components on the engine till i know whether I can return it. However I have thought about going with a larger jet. The throttle I believe is opening all the way. It is actually all the way open at about 3/4 throttle on the throttle control. Turning the throttle control more than that does not increase rpm or change sound of engine at all. The manufacture states that this is normal behavior and that at about 3/4 throttle on the throttle control is actually full throttle.
I would love to test more of these engines to see how they rate comparatively. When it was just mine I thought something was mechanically wrong with it. After testing the second one and getting the same test results I am no longer convinced that it is broken or malfunctioning. Just weak, as in it just runs weak from the factory.