55.2-59 "Octane adjustment knob"

[whitedog76]

Wasn't it used for summer/winter tuning? Advance in the winter, retard in summer.

[BlouDon]

Originally Posted by whitedog76

Wasn't it used for summer/winter tuning? Advance in the winter, retard in summer.

Assuming fuel octane remains constant, the only way in which winter vs summer can play a role is when it comes to intake air temperatures. This engine has a rather low compression ratio, so it would really require very low octane fuel and rather high intake temps (30ºC or more) to make this engine detonate.

Having set the timing as per the book, timing would be very far away from detonation. I've advanced mine quite a bit which has added at least "1 horse" to the power output - but with so little, every bit helps. I also live at 1400m AMSL which calls for at least another 4 degrees of advance.

I'm running mine on 93 Octane (If that can be believed) and in our high summer temps (30ºC or more) there is no sign of detonation yet - even with timing rather aggressively advanced.