ORIGINAL: Evil Homer
How do you adjust the advance on these, the pickup is fixed to the crankshaft and the pick up point is dependent on the way the back plate is installed, there is no way to move or adjust it mechanically that i can see.
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You can't, so you are going to have to reduce the load on the engine. Lower the demand the prop places on the engine by reducing pitch/diameter. As mentioned previously, this engine likes to rev up a bit.
Yes, you may have gotten away with running too much prop under certain conditions, but you may be right on the edge where ambient weather conditions can push the engine into running too hot (in terms of spark advance with a given load).