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Now although that statement had to do with a topic about removing the TPS, I recall in other posts of his that the 270 degree motors do not benefit from raising the rev limiter, because they'll cut out at 8100 rpm no matter what you do.



So, if I read this correctly, even with no limiter, the engine won't turn over 8100? And, that is because the engine cuts off as if it had a rev limiter? And, the 360 degree engine doesn't?
OK, looking at the differences, the America/SM 800 engines have a little milder exhaust cam timing and the different crank. The crank causes some differences in the ignition operation. The only way they would be able to sort out the ignition timing accurately enough is to have 2 crank position indicator lugs on the alternator rotor. Cranking speed variations would prevent sorting out which indicator is which, so the coils are undoubtedly fired twice per revolution while the 360 engine fires once per revolution. This reduces the effective dwell angle, especially on the leading cylinder. So, you'd have to use a very different coil design or re-engineer the entire ignition system to get as good a spark on the 270 degree engine.
Another possible factor is that the off spark on the 360 engine occures at the top of the exhaust stroke while, on the 270 engine, one occures in the middle of the exhaust stroke and, on the other cylinder, the middle of the intake stroke. That might not be such a big deal with 2 carburettors, but I know for certain it can cause a V-twin to pook out the carb when the mixure is just right.

As for mucking about with the TPS, that is only used to estimate the load on the engine and adjust the advance curve. For example, if the engine is holding at 4500 and the throttle is wide open, it is a safe bet that it is under a tremenduous load and the ignition should be retarded a bit. Think of this as the vacuum advance on older car engines.

Let's hope there's intelligent life somewhere in space 'cause it's buggar all down here. -- Monte Python