"Calorific Value" has absolutely nothing to do with jetting.  Stoichometric air to fuel ratio is what is critical.

For example, propane contains about 22% less energy ("net calorific value") per gallon than gasoline but actually burns leaner with an optimal air/fuel ratio of about 15.5 to 1 compared to about 14.7 to 1 for gasoline. 

The same engine run on propane will always have less power than the same engine run on gasoline.  Fact.

If you tried to jet a propane engine richer to make up for the lower calorific value?  You'd just have a rich running engine that wastes fuel and has even LESS power. 

Ethanol is a different case. Ethanol does have less energy per gallon (slightly less that propane) BUT the stoichometric air/fuel ratio for ethanol is about 9 to 1 vs 14.7 to 1 for gasoline.  So an engine run on ethanol needs to be jetted much richer than one on gasoline for a "perfect" burn. 

The difference in energy between gasoline and ethanol is less than the amount extra you need to burn to get the mixture right so Ethanol inherently makes more power than gasoline. 

There are other complexities like burn rate and octane rating than affect the power a fuel can produce in an internal combustion engine, but the above are the facts regarding calorific value. 

The stoichometric ratio for E10 is about 14.1 to 1.  So if you have a 30 pilot jet, you'd need like a 31.5 pilot to compensate for E10.  Next step is a 35. 

It's absolutely true that you jet an engine for what it needs. 

Just don't blame it on using E5 or E10 or some BS about "calorific value". 

That's useful info thanks!

we have many outlets in my town for non ethanol unleaded. And any old gas (1 week or more) goes in the mower. so fuel is always fresh. also I do not use any "snake oil" additives in the fuel. just good old 2S or 2R. also, I have just purchased a 1975 MX 400, so I will be going thru this again soon armed with the knowledge gained here. Starting with a brand new Mikuni 38 on that one.

Your motor will last far longer if you can avoid ethanol type fuels. They tend to dissolve 2T oil, and not a good idea if there is an alternative.